Adverse Childhood Experiences and Bullying During Adolescence: A Systematic Literature Review of Two Decades

Abstract

There is a need for a comprehensive understanding of the relationship between adverse childhood experiences (ACEs) and the emergence of bullying behaviors in adolescence, as well as their subsequent implications for youth well-being. This study systematically reviewed the link between 11 unique ACEs (including the original 10 from the 1998 CDC-Kaiser ACE study plus child welfare involvement) and three specific bullying behaviors (i.e., perpetration, victimization, and bully-victim) over two decades (1999–2019). Five databases (i.e., Embase, ERIC, PsycINFO, PTSDpubs, and PubMed) were used to identify 51 studies. The findings showed a consistent pattern of positive associations for certain ACEs, specifically cumulative ACEs, maltreatment, family violence, physical abuse, and domestic violence, with bullying perpetration and victimization. However, sexual abuse and divorce and separation were not consistently related to perpetration or victimization. In addition, general abuse was positively associated with perpetration, whereas emotional abuse and children in the welfare system tended to be victims rather than perpetrators of bullying. Notably, several ACEs, including neglect and household dysfunction, remain largely understudied in relation to bullying. The research also predominantly focuses on bullying perpetration and victimization, with bully-victims receiving much less attention. Finally, the research on the impact of bullying behaviors on the well-being of youth with ACEs is too limited to make definitive conclusions regarding the mediating or moderating role of bullying on youth well-being outcomes. The results underscore the importance of understanding and accounting for the simultaneous and cumulative effects of ACEs. This understanding is essential when designing trauma-informed interventions and prevention strategies to combat bullying. Future longitudinal studies should rectify methodological and psychometric shortcomings, investigate potential mediators and moderators, and integrate health outcomes of positive experiences with adverse childhood experiences to capture shared risk and resilience pathways.

Introduction

Bullying behaviors typically peak in adolescence (Dake et al., 2003) and have lasting negative effects on youth well-being for both perpetrators and victims (Halliday et al., 2021; Rigby, 2003). Adverse childhood experiences (ACEs) have been examined as risk factors for bullying behaviors, given their established links to broader spectrums of violence and victimization (Pournaghash-Tehrani & Feizabadi, 2009; Whitfield et al., 2003). While there is evidence that some ACEs are positively related to bullying behaviors (e.g., Hong & Espelage, 2012; Lee et al., 2022; Lereya et al., 2013), it is unclear whether these positive associations extend to all 10 ACEs as investigated in the seminal US CDC-Kaiser ACE Study (Felitti et al., 1998). Further, there is potential heterogeneity across ACEs in terms of their associations with bullying (Felitti et al., 1998). For example, certain deprivation- versus threat-related ACEs may have a stronger association with bullying victimization compared to perpetration and vice versa (Hildyard & Wolfe, 2002; McLaughlin et al., 2014). As such, there is a need for a more nuanced and comprehensive understanding of the associations between ACEs and bullying behaviors. The current study addresses this gap by systematically reviewing and synthesizing two decades of research following the CDC-Kaiser ACE study, examining the associations of 11 ACEs (10 ACEs from the CDC-Kaiser ACE study plus child welfare involvement) with bullying perpetration and victimization during adolescence as well as the mediating and moderating role of bullying behaviors on the well-being of youth with ACEs.

Bullying, a widespread public health issue (Olweus, 1978; Center for Disease Control and Prevention [CDC], 2011), is a significant challenge impacting youth’s well-being globally. Bullying often develops during childhood, peaks in adolescence, and typically occurs within a school environment (Dake et al., 2003). There is a significant percentage of youth involved in bullying, though prevalence rates vary across studies. For instance, a notable 2009 large international study showed that approximately 27% of youth reported being involved in bullying, with 10.7% as perpetrators, 12.6% as victims, and 3.6% as bully-victims (Craig et al., 2009). In the US, the 2009 National Crime Victimization Survey showed that 28% of youth ages 12–18 reported some form of bullying victimization; more recent data from 2019 indicated that 22% of youth reported bullying victimization (National Center for Education Statistics, 2022).

The American Educational Research Association (AERA) adopted a standardized definition of bullying in 2013 to address varying prevalence rates and foster consistency in psychometric measurement. Specifically, the definition of bullying includes three characteristics that distinguish it from general aggression: an intent to cause harm, a power differential (either physical or social), and aggressive behavior that is repeated or likely to be repeated (AERA, 2013). The CDC further defines bullying as “any unwanted aggressive behavior(s) by another youth or group of youth who are not siblings or current dating partners that involves an observed or perceived power imbalance and is repeated multiple times or is highly likely to be repeated” (Gladden et al., 2014, p. 7). Bullying perpetration can be direct, confronting the victim, or indirect, without direct communication. There are three forms of bullying: physical (e.g., physical aggression), verbal (e.g., oral or written communication), and relational (e.g., harming one's reputation and relationships; Gladden et al., 2014). Youth can be an aggressor or perpetrator of bullying, a victim or target of bullying, or a bully-victim and experience both perpetration and victimization. The current review focused on these three subtypes of bullying behavior (i.e., perpetrators, victims, and bully-victims).

Research indicates that bullying perpetration and victimization can have lasting adverse effects on youth. Perpetrators of bullying report higher rates of anxiety, low social skills, delinquency, and substance use, to name a few (Hamstra & Fitzgerald, 2022; Jones et al., 2019; Walters & Espelage, 2019). Victims of bullying report higher rates of depression, anxiety, and suicidality, as well as lower quality of life, social support, and academic achievement (Hansen et al., 2012; Laith & Vaillancourt, 2022; Takizawa et al., 2014). Bully-victims typically have worse psychosocial adjustment outcomes than perpetrators or victims alone (Nansel et al., 2004), potentially stemming from low emotion regulation skills combined with high aggressive-impulsive behaviors (Schwartz et al., 2001).

ACEs are pervasive traumatic events that occur during childhood and adolescence and have a lasting impact on an individual’s well-being across the lifespan (Dube, 2018, 2019; Felitti et al., 1998). ACEs are common, with nearly two-thirds of the population experiencing at least one ACE and over 15% reporting four or more (CDC, 2023). Numerous systematic reviews and meta-analyses consistently show links between ACEs and a range of psychosocial, behavioral, and health outcomes, including substance use; sexual, mental, and physical health problems; obesity and weight problems; diabetes; behavior problems; victim of violence; and lower overall quality of life (Hao et al., 2015; Hughes et al., 2017; Patruccelli et al., 2019). During adolescence, the impact of ACEs often manifests as behavioral risks such as aggression, antisocial behavior, substance use, and sexual risk behaviors that can persist into adulthood (Dube, 2018).

According to the landmark CDC-Kaiser ACE study (Dube et al., 2003; Felitti et al., 1998), there are 10 specific ACEs: physical, sexual, and emotional abuse; physical and emotional neglect; witnessing domestic violence; caregiver substance misuse; household mental illness; parental separation and divorce; and parental incarceration. The current review defines ACEs as these 10 specific ACEs, plus child welfare involvement, as well as their various combinations and the cumulative score of all ACEs (see Fig. 1). Child welfare involvement (e.g., child protective service investigation) was included as an additional ACE, considering the high prevalence rate of ACEs among this population (Turneya & Wildeman, 2017) as well as research examining bullying in the context of child welfare involvement without analyzing a specific ACE as defined in the CDC-Kaiser ACE study. For example, Mohapatra et al. (2010) found that family child protective services involvement was associated with higher odds of youth bullying victimization; including such research allowed this review to be more inclusive.

Fig. 1

The singular and combined ACEs included in this review

Considering ACEs' documented associations with broader forms of violence and victimization (Pournaghash-Tehrani and Feizabadi, 2009; Whitfield et al., 2003), it is not surprising that ACEs have been examined as potential risk factors for bullying behaviors (Duke et al., 2010). This is also consistent with social learning theory, such that youth may internalize the violence they witness at home or experience with their caregivers and may learn that aggression is an acceptable way to interact with peers. From this perspective, the family context contributes to the learning and maintenance of aggressive behaviors, and caregivers act as a model that youth reference in future interactions and relationships (Bandura, 1978).

Empirical evidence has documented positive associations between certain ACEs and bullying behaviors. For instance, in a literature review that examined social-ecological factors associated with bullying, Hong and Espelage (2012) noted consistent positive associations between exposure to interparental violence and both bullying perpetration and victimization. Similarly, in a recent systematic review including 14 studies, Lee et al. (2022) found that most of the studies reported significant positive associations of intimate partner violence exposure with bullying perpetration (75% of articles) and victimization (70% of articles). Further, in a meta-analysis that examined parenting behaviors on bullying victimization and bully-victims, Lereya et al. (2013) showed that negative parenting behaviors, including parental abuse and neglect (i.e., two ACEs), were positively associated with bullying victimization and bully-victims. The effects were generally small to moderate (Hedge’s g range: 0.10–0.31) for victims and moderate for bully-victims (Hedge’s g range: 0.13–0.68; Lereya et al., 2013).

However, the etiological mechanisms underlying the links between various ACEs and bullying behaviors may differ across ACEs (Felitti et al., 1998; Hildyard & Wolfe, 2002; McLaughlin et al., 2014). Some ACEs might influence social development, causing externalizing issues and leading to bullying perpetration and aggression (Felitti et al., 1998; Hong et al., 2012). Conversely, other ACEs could cause emotional challenges, such as internalizing problems, leading to victimization (Christina et al., 2021; Felitti et al., 1998). Further, according to the dimensional model of ACEs and psychopathology by McLaughlin et al. (2014), ACEs can be classified into threat and deprivation categories. Experiences of these different categories of ACEs have differential implications for youth’s peer interactions, which may further affect their likelihood of becoming a bully perpetrator, victim, or bully-victim. For example, neglected youth (i.e., deprivation category) are more likely to withdraw from peers than abused youth (i.e., threat category; Hildyard & Wolfe, 2002) and thus may be more likely to be victims than perpetrators of bullying. Further, prior research contends that multiple ACEs should be considered as risk factors for violent adolescent outcomes, including bullying (Duke et al., 2010). Thus, it is critical to examine the relations between all the different ACEs and bullying behaviors rather than generalizing findings about the associations of some ACEs with bullying to other ACEs.

Despite robust reviews and meta-analyses examining the associations between ACEs and bullying, research has typically focused on a single or small number of ACEs in terms of their associations with bullying. No systematic review has synthesized the associations of all 10 ACEs from the CDC-Kaiser ACE study (Dube et al., 2003; Felitti et al., 1998) with the three subtypes of bullying behaviors (i.e., perpetrators, victims, and bully-victims) during adolescence. Thus, the current review adds to the literature by providing the first systematic review of quantitative evidence regarding the associations of all 10 ACEs from the CDC-Kaise ACE study, plus child welfare with bullying behaviors.

Current Study

In light of the potential heterogeneity in the associations between ACEs and bullying behaviors and the lack of a systematic understanding of these associations, the primary goal of this study was to provide a comprehensive synthesis of two decades of literature on the associations between ACEs and bullying behaviors during adolescence. Specifically, the current systematic review examined this research question: Do the associations between ACEs and bullying behaviors differ across various ACEs? Said differently, are some ACEs associated with bullying perpetration and others related to victimization? Previous research indicates positive associations between some specific ACEs and bullying behaviors. However, it is also possible that divergent pathways exist through which specific ACEs link to bullying behaviors. Literature that examined the mediating and moderating effects of bullying in the associations of ACEs with a variety of youth psychosocial outcomes is also included.

Method

Search Strategy

A systematic literature review was conducted as part of a more extensive search that explored the associations between ACEs and peer relationships. This search identified two distinct groups of studies: (1) bullying (n = 51) and (2) general peer relationships (n = 92). Thus, the review was separated into two manuscripts. This paper reports the 51 records on bullying and the 92 records on general peer relationships are documented in J. H. Wang et al. (2023).

Five databases were searched for the project: Embase (September 24, 2019), ERIC (September 30, 2019), PsycINFO (September 30, 2019), PTSDpubs (September 30, 2019), and PubMed (October 13, 2019). Search terms focused on three categories: ACEs, peer relations, and age range, and they were combined by the Boolean operator AND (see Supplemental Appendices A and B for specific search terms). The qualifier [All Fields] or its equivalent (e.g., [Anywhere] in PTSDpubs) was used, except for PubMed, in which the qualifier [Mesh] in addition to [All Fields] was used when relevant (see Supplemental Appendix B). Two limiters were used: (1) the year of publication was between 1999 and 2019, and (2) the publication was in English.

Data Screening

DistillerSR (Version 2.39.0), a software for systematic reviews, was utilized for screening. First, duplicates were removed, and the second author completed the title screening. Next, multiple pairs of two independent reviewers assessed articles through abstract and full-text screenings. To ensure inter-researcher agreement, each researcher achieved 80% agreement with the second author on practice articles prior to beginning screenings. Reviewers also met weekly to review progress and discuss questions. Inter-researcher agreement was above 80% across all weeks of screenings (abstract screening: 81–95% across 11 weeks; full-text screening: 83–92% across 8 weeks). At the end of each screening phase, reviewers discussed discrepancies until a consensus was reached and involved a third reviewer when necessary. On a few occasions, when a consensus could not be reached with the third reviewer, that article was included.

Eleven singular ACEs (i.e., 10 ACEs in the CDC-Kaiser ACE study plus child welfare involvement), as well as their various combinations, were included (see Fig. 1). In terms of the combined ACEs, maltreatment refers to combinations of neglect (physical, emotional) and abuse (physical, sexual, emotional). Household dysfunction included a combination of the following ACEs: witnessing domestic violence, caregiver substance misuse, household mental illness, parental divorce and separation, and parental incarceration. Further, composite ACEs referred to combinations of ACEs from the maltreatment and household dysfunction categories. Lastly, family violence includes a combination of experiencing abuse and witnessing domestic violence.

ACE definitions were slightly modified from the CDC-Kaiser ACE study. Specifically, “mother treated violently” was expanded to include other types of domestic violence (e.g., no specification of the domestic violence perpetrators; fathers treated violently). Further, this review focused on ACEs related to or perpetrated by caregivers, except sexual abuse. Therefore, ACEs not related to or caused by caregivers (e.g., community violence, sibling substance misuse, school violence) did not meet this review’s inclusion criterion on ACEs. In terms of sexual abuse, there was often no information regarding who the perpetrators were. Thus, all references were included unless there was information that it was sexual victimization perpetrated by peers.

Abstract screening used the following criteria for inclusion (see Supplemental Appendix C for protocol): (1) empirical research; (2) ACEs were studied during birth through adolescence; (3) peer relations were studied during adolescence; and (4) the study examined an association between ACEs and peer relations, with peer relations examined as a dependent variable or as a moderator on the association between ACEs and other youth outcomes. A screening criterion for assessing peer relations as a mediator (or indirect effect) was not set because all mediation analyses were included based on the criterion that they examined the relationship between ACEs and peer interactions.

Full-text screening added the following criteria beyond those in abstract screening (see Supplemental Appendix D for protocol): (1) English full-text, (2) publication in peer-reviewed journals, and (3) quantitative research. A cut-off range for adolescence (10 years 0 months to 19 years 11 months; World Health Organization, n.d.) was set. Peer relation variables and moderated youth outcomes had to be measured during 10–19 years.

Data Extraction and Synthesis

Data extraction was also conducted via DistillerSR (Version 2.39.0). The first two authors conducted data extraction; each extracted half of the data and verified the data extracted by the other author. Conflicts in data extraction were resolved weekly. Studies were further excluded that only reported bivariate correlations between ACEs and peer relationships. In addition, the definition of caregiver substance misuse was aligned better with the CDC-Kaiser ACE study by including only studies that suggested problematic substances (i.e., general substance use such as smoking was considered insufficient to meet the inclusion criterion on ACE). Further, a p-value of 0.05 was used to evaluate statistical significance, although other values might have been used by the original authors (e.g., p < 0.10). Finally, the following information was extracted from each study: authors, year, country, research goals, sample information, design, analytic strategies, ACE measures, peer relation measures (including bullying), and key findings (see Supplemental Table S1). There were two marginal cases, the details of which are described in Appendix E. Thematic analysis was utilized to make sense of the findings. Specifically, the first two authors discussed and synthesized the prominent themes of the key findings across studies throughout the data extraction phase and further consolidated these themes after completing data extraction (Braun & Clarke, 2023; Goagoses & Koglin, 2020).

Quality Assessment

The 14-item checklist developed by (Kmet et al., 2004) was used to evaluate the quality of the included articles. This checklist was initially developed for experimental designs. Three of the 14 items were irrelevant to the current search and excluded (i.e., random allocation, blinding of subjects and investigators). Each item was rated as N/A, No (0), Partial (1), or Yes (2). The total quality score for each study was the total sum divided by the total possible sum, with a possible range of 0–100%. Theoretically, the higher the total quality score, the higher the quality of a study. The first two authors independently evaluated each study, discussed discrepancies, and reached 100% agreement across all included studies.

Results

Study Inclusion

The larger search went through five phases, reducing the number of records from 47,241 to 140, which was summarized in a PRISMA diagram for systematic review (see Fig. 2; Page et al., 2021). Studies were excluded if they did not meet all inclusion criteria as described above. The number of studies excluded at each phase was as follows: de-duplicating (n = 13,705), title screening (n = 28,731), abstract screening (n = 4,069), full-text screening (n = 520), and data extraction (n = 76). Among the final 140 records with data extracted, 51 on bullying were reported in this study, and 92 on general peer relationships were described in J. H. Wang et al. (2023).

Fig. 2

PRISMA flowchart of the search

Study Characteristics

A summary of the 51 included studies is provided in Table 1 (see Supplemental Table S1 for more details). There was an increasing trend in the number of publications since the first study was published in 2005 (see Fig. 3). The studies were conducted in 22 countries or regions across continents. The US had the most studies (n = 14), followed by Brazil (n = 5), Canada (n = 3), South Korea (n = 3), and Sweden (n = 3). The following countries or regions had two studies each: China, Finland, Norway, South Africa, Taiwan, and the UK. Further, the following countries contributed one study each: Cambodia, France, Ireland, Israel, Japan, Malawi, Mexico, Spain, The Netherlands, and Vietnam. Lastly, one study had participants from both the US and Puerto Rico.

Table 1 Overview of the included studies

Fig. 3

Number of included articles per year

The quality assessment total score ranged from 0.59 to 1.00 across studies, with a mean of 0.81. Readers are recommended to interpret the total score in the context of a study’s methodology (e.g., design and analyses) and the quality scores at the item level (see Table 2). Some studies had a high total quality score due to their high quality, whereas others received a high score because their methodology was simple and multiple items were not applicable. The scores for the 11 items ranged from 0.82 (outcome measure) to 1.98 (study objective).

Table 2 Item-level quality assessment scores of the included studies

Study Results

The results are organized in two sections: (1) the associations between ACEs and bullying (i.e., the main effect) and (2) the mediating and moderating roles of bullying. The main effect section is further organized by the three bullying behaviors (perpetration, victimization, and bully-victims) and then by ACEs (first combined ACEs and then singular ACEs) when appropriate. Results are described in a separate subsection when there are at least two studies on the association between an ACE and bullying behavior. ACEs with only one study are presented at the end of one subsection. Additionally, the main effect section reported links between the independent variables (i.e., ACEs) and mediators (i.e., bullying) of the mediation models. The term “special sample” refers to samples recruited from non-school or community settings or a unique cultural context.

Associations Between ACEs and Bullying Behavior

Across the 11 singular and six combined ACEs (see Table 3), physical abuse was most studied in relation to bullying (n = 16), followed by domestic violence (n = 13), sexual abuse (n = 11), emotional abuse (n = 8), divorce and separation (n = 8), abuse (n = 6), and family violence (n = 6). The remaining ACEs had three or fewer studies, and household dysfunction had no studies.

Table 3 Number of studies and analyses regarding the relations of ACEs with bullying perpetration, victimization, and bully-victims

Associations Between ACEs and Bullying Perpetration

There were 34 studies, primarily cross-sectional (cross-sectional, n = 27; longitudinal, n = 7), that examined the associations between ACEs and bullying perpetration. Some studies investigated multiple ACEs in relation to bullying perpetration. For instance, Williamson et al. (2018) examined the relations of four ACEs (i.e., physical abuse, sexual abuse, emotional abuse, and domestic violence) with bullying perpetration. This led to a total of 59 associations analyzed (i.e., 41 positive, 17 nonsignificant, and one negative) across all studies. Across all ACEs (see Table 3), cumulative ACE score (or composite ACEs), maltreatment, and family violence were positively associated with bullying perpetration across all studies. Abuse, physical abuse, and domestic violence appeared to be positively related to bullying perpetration, as most studies found positive associations, and the few studies that reported nonsignificant associations could be explained by methodological features. The associations between the remaining ACEs and bullying perpetration were not studied at all or appeared to be inconclusive either because the total number of included studies was too small or the results were split between positive and nonsignificant relations.

Overall, sample sizes appeared adequate, considering the complexities of most models. Samples were mainly recruited from schools or communities, with a few studies recruited from special groups, including a psychiatric youth sample (Mustanoja et al., 2011), youth involved with child welfare (Sterzing et al., 2020), and youth offenders (Viljoen et al., 2005). The predominant analytic strategy was logistic regression, although other analyses were used, such as the Chi-square test, the Kruskal–Wallis H test, linear regression, multilevel modeling, manifest path analysis, and structural equation modeling (SEM) with latent variables. The primary method of assessing bullying perpetration was self-report, except for three studies that included either parent report (Morcillo et al., 2015; Odar Stough et al., 2016) or peer nomination (Wei & Lee, 2014). Further, many studies utilized single-item measures (e.g., Duke et al., 2010) or lacked psychometric information (e.g., CDC, 2011), although multi-item measures were used in other studies (e.g., Espelage et al., 2014). Lastly, only seven of the 34 included studies were longitudinal, with three examining family violence (Espelage et al., 2014; Grant et al., 2019; Low & Espelage, 2013), two on domestic violence (Knous-Westfall et al., 2012; Le et al., 2017), one on abuse (Hong et al., 2017), and one on divorce and separation (Wei & Lee, 2014). Thus, although a pattern of positive associations was reported for multiple ACEs (e.g., cumulative ACE score), it is largely unknown the extent to which ACEs are associated with bullying perpetration over time.

Composite ACEs. All three cross-sectional studies reported positive associations between cumulative ACE scores and bullying perpetration. Specifically, Duke et al. (2010) reported that the cumulative ACE score was positively related to bullying perpetration. Further, the likelihood of perpetration increased two fold for girls and 2.7 fold for boys when youth had four or more ACEs, compared to peers with no ACEs. Further, Reisen et al. (2019) found that bullying perpetrators were more likely to report total adversity (i.e., OR = 5.8 for 4–10 ACEs, OR = 2.3 for 1–3 ACEs). Finally, Forster et al. (2020) reported that an increase from 0 to 6 ACEs was associated with higher physical bullying perpetration probability, although an increase in ACEs was not significantly related to relational bullying perpetration.

Maltreatment. Positive relations between maltreatment and bullying perpetration were found across all three cross-sectional studies. The definition of maltreatment (i.e., a combination of abuse and neglect) differed slightly across studies as G.-F. Wang et al. (2019) included sexual abuse, and the other two studies did not (Holt et al., 2009; X. Wang et al., 2017). Specifically, G.-F. Wang et al. (2019) reported that maltreatment was associated with higher odds of being in the bully group compared to the non-involved group for each form of school bullying (i.e., physical, verbal, relational, and cyber). Holt et al. (2009) found via a Chi-square test that bullies were more likely to report maltreatment. Lastly, using SEM, X. Wang et al. (2017) reported that maltreatment was positively related to concurrent bullying perpetration.

Family Violence. Positive associations between family violence and bullying perpetration were reported in all five studies (three longitudinal; two cross-sectional) that utilized various analyses (i.e., multilevel modeling, SEM, regression, logistic regression). Two cross-sectional studies conducted logistic regression and reported that family violence was associated with increased odds of bullying perpetration (Fitzpatrick et al., 2007; Fujikawa et al., 2016). Of note, Fitzpatrick et al. (2007) analyzed a predominantly African American sample and Fujikawa et al. (2016) examined a Japanese sample.

In a longitudinal study (3 waves across 3 semesters) with baseline bullying perpetration controlled, Low and Espelage (2013) found that Wave 1 family violence positively predicted Wave 3 non-physical bullying perpetration. However, this association became nonsignificant when additional control variables were added to the model (i.e., depression, substance use, hostility). Wave 1 family violence was not significantly related to Wave 3 cyberbullying perpetration (Low & Espelage, 2013). In another longitudinal study (3 waves across 3 semesters) that examined the mediating role of bullying perpetration on the relation of family violence with youth substance use, Espelage et al. (2014) conducted SEM and reported that family violence was positively associated with later bullying perpetration. In the last longitudinal study (4 waves across 2 years) with multilevel modeling, Grant et al. (2019) found that between-person family violence predicted increases in bullying perpetration over time, and within-person family violence was positively associated with concurrent bullying perpetration. Of note, these three studies were conducted by the same research group. Further, Low and Espelage (2013) and Espelage et al. (2014) analyzed the same dataset.

Abuse. Abuse had positive relations with bullying perpetration in two studies but nonsignificant associations in one study that used a limited measure for perpetration. Specifically, Shamu et al. (2016) found via SEM that abuse (i.e., physical, emotional, and sexual) was positively related to concurrent bullying perpetration. Hong et al. (2017) reported in a longitudinal study through path analysis that abuse (i.e., physical and emotional) was positively associated with later bullying perpetration. Lastly, Lepistö et al. (2012) suggested that family abuse (i.e., physical and emotional) was not related to concurrent bullying perpetration utilizing multivariate analyses. Of note, a single-item dichotomized measure was used to assess bullying perpetration in Lepistö et al. (2012), whereas Hong et al. (2017) and Shamu et al. (2016) both utilized multi-item measures.

Physical Abuse. Physical abuse was positively related to concurrent bullying perpetration across six studies that analyzed school or community samples but was not significantly associated with concurrent bullying perpetration in the three studies that had special samples. Specifically, physical abuse was associated with increased odds of bullying perpetration in the three studies utilizing logistic regression (CDC, 2011; Duke et al., 2010; Lucas et al., 2016). Physical abuse was also positively related to bullying perpetration in studies utilizing SEM (Min et al., 2015), path analysis (Williamson et al., 2018), and regression (I. R. de Oliveira et al., 2018). These six studies included various control variables in their models, including witnessing domestic violence (CDC, 2011), neglect and emotional abuse (Min et al., 2015), and demographic variables (Duke et al., 2010). All six studies analyzed school or community samples.

The remaining three studies conducted logistic regression in special samples and showed nonsignificant relations between physical abuse and bullying perpetration (Ameli et al., 2017; Mustanoja et al., 2011; Sterzing et al., 2020). Of note, Ameli et al. (2017) was the only one of the nine studies that recruited a sample from an African country (i.e., Malawi). Possible cultural and linguistic differences in the measurement of physical abuse and bullying perpetration might explain the nonsignificant finding. Mustanoja et al. (2011) analyzed a psychiatric sample, and Sterzing et al. (2020) examined a female-only sample with half of the participants involved with child welfare. Such sample characteristics differ from the school or community samples in the six studies above that reported positive associations and may help explain the observed differences.

Sexual Abuse. Eight cross-sectional studies examined the associations between sexual abuse and bullying perpetration, four of which reported positive relations, and four reported nonsignificant findings. The four studies reporting positive associations utilized Chi-square tests or logistic regression and did not control ACEs other than sexual abuse in analyses, which might have impacted the results. The diverse sample characteristics (e.g., school, community, youth offenders, child welfare, and psychiatric) and measurement strategies across the eight studies might have also contributed to the heterogeneity in the findings. Specifically, using a Chi-square test, Viljoen et al. (2005) found in a sample of youth offenders that bullies were more likely to report sexual abuse than non-involved youth. Holmberg and Hellberg (2010; Chi-square test) reported in an all-female school sample that girls who had been sexually abused were more likely to report bullying perpetration than their non-abused counterparts. Duke et al. (2010) found in a school sample that sexual abuse was related to increased odds of bullying perpetration. Further, Mansbach-Kleinfeld et al. (2015) reported in a community sample that sexual abuse was related to higher odds of bullying perpetration.

The remaining four studies indicated nonsignificant associations between sexual abuse and bullying perpetration. Specifically, Mustanoja et al. (2011) found that sexual abuse was not significantly related to the odds of bullying perpetration in a psychiatric youth sample with physical abuse and witnessing interparental violence (i.e., another two ACEs) controlled. Williamson et al. (2018) indicated that sexual abuse was not associated with bullying perpetration through path analysis with multiple ACEs (i.e., domestic violence exposure and emotional and physical abuse) controlled. Sterzing et al. (2020) discovered that youth with sexual abuse were not more likely to be bullies compared to non-involved youth in an all female sample, with approximately half involved with the child welfare system. Lastly, Mignot et al. (2018) found that sexual abuse was not related to bullying perpetration. Of note, single-item measures were used to measure sexual abuse and bullying perpetration by Mignot et al. (2018).

Emotional Abuse. The associations between emotional abuse and bullying perpetration appeared mixed across the six cross-sectional studies (positive, n = 3; nonsignificant, n = 3). Of note, the studies showing positive associations utilized univariate regression strategies (i.e., linear regression, logistic regression), whereas studies indicating nonsignificant findings used multivariate analyses (i.e., SEM, path analysis) or a special sample. Specifically, Ameli et al. (2017) reported that emotional abuse was associated with higher odds of bullying perpetration among girls but not boys, with other ACEs (i.e., domestic violence, physical abuse) controlled. Lucas et al. (2016) found that emotional abuse was related to higher odds of bullying perpetration. Further, I. R. de Oliveira et al. (2018) reported that emotional abuse was positively associated with being a bully via linear regression with demographic variables but no other ACEs controlled.

The remaining three studies suggested nonsignificant associations. Specifically, Williamson et al. (2018) reported that emotional abuse was not associated with bullying perpetration in a path analysis with other ACEs controlled (i.e., domestic violence exposure, physical and sexual abuse). Min et al. (2015) found that emotional abuse was not related to bullying perpetration via SEM with neglect and physical abuse controlled. Lastly, Sterzing et al. (2020) reported that youth with emotional abuse were not more likely to be bullies via logistic regression in an all-female sample, with about half involved with the child welfare system.

Domestic Violence. Findings were fairly consistent that domestic violence was positively associated with bullying perpetration, as positive associations were reported in nine of the 12 studies with different control variables included (e.g., no control variables, demographic variables only, and demographic and other ACE variables). However, it is unclear how witnessing domestic violence affects youth bullying perpetration across adolescence, as the predominant design was cross-sectional (n = 10). Further, most studies utilized simple analyses like logistic regression (n = 8) or Chi-square tests (n = 2).

Specifically, three cross-sectional studies conducted logistic regression with various ACEs controlled in the models (i.e., physical abuse, CDC 2011; parental mental health, Odar Stough et al., 2016; physical and emotional abuse, Lucas et al., 2016), all of which reported a positive association between witnessing domestic violence and the concurrent odds of bullying perpetration. Two cross-sectional studies conducted logistic regression without controlling any other ACEs but also reported a positive relation between witnessing domestic violence and the odds of bullying perpetration (W. A. de Oliveira et al., 2016; Duke et al., 2010). Two additional cross-sectional studies found that bullies were more likely to report domestic violence exposure via Chi-square tests (Holt et al., 2009; Viljoen et al., 2005).

Further, two longitudinal studies showed positive associations between domestic violence exposure and bullying perpetration. Le et al. (2017) explored bullying stability through a short-term longitudinal design (i.e., 2 waves across 6 months) and logistic regression in a Vietnamese school sample. They found that witnessing interparental violence (IPV) was associated with decreased odds in the stable low group of bullying perpetration and increased odds in the declining group but not related to the increasing group. The increased odds in the declining group may have been due to the high baseline level of bullying perpetration in participants who had witnessed IPV. In another longitudinal study that spanned 6–7 years, Knous-Westfall et al. (2012) reported through regression that witnessing severe IPV where an injury was present predicted higher rates of relational bullying perpetration in boys and girls, and higher rates of overt bullying in boys only, although witnessing any type of IPV was not significantly associated with later bullying perpetration (i.e., overt or relational). Of note, Knous-Westfall et al. (2012) did not control for baseline levels of bullying perpetration.

The remaining three studies showed nonsignificant associations between witnessing domestic violence and concurrent bullying perpetration. Specifically, Williamson et al. (2018) reported that domestic violence exposure was not significantly related to bullying perpetration in a path analysis with three other ACEs controlled (i.e., physical, sexual, and emotional abuse). Similarly, Ameli et al. (2017) reported in a Malawi sample that domestic violence exposure was not associated with the odds of bullying perpetration with other ACEs (i.e., physical and emotional abuse) controlled. Lastly, Mustanoja et al. (2011) reported in a psychiatric sample that witnessing IPV was not related to the odds of bullying perpetration, with physical and sexual abuse controlled.

Caregiver Substance Misuse. Mixed results (i.e., positive and nonsignificant) were suggested regarding the associations between caregiver substance use and bullying perpetration in two cross-sectional studies with logistic regression. Specifically, Duke et al. (2010) reported in a US school sample that family alcohol and drug use was associated with increased odds of bullying perpetration, with demographics controlled. Morcillo et al. (2015) found in a sample of Puerto Rican children living in the US or Puerto Rico that parental substance use was related to higher odds of bullying perpetration with demographic variables controlled. However, this association became nonsignificant once child characteristic variables (i.e., early aggression, academic achievement) were added to the model. Thus, the positive association reported by Duke et al. (2010) may have been an artifact of only including demographic controls.

Household Mental Illness. Two studies reported mixed results (i.e., negative and positive) regarding the associations between household mental illness and bullying perpetration. Both studies conducted cross-sectional logistic regression and used parent-reported single-item measures of bullying perpetration. However, they used different definitions and measurements of parental mental health, which may explain the discrepant findings. Specifically, in a national sample of normal weight, overweight, and obese youth, Odar Stough et al. (2016) found that youth whose mothers had poor mental health were less likely to be a bully, with multiple variables controlled (e.g., domestic violence exposure). However, paternal mental health was not associated with bullying perpetration. In a sample of Puerto Rican children living in the US or Puerto Rico, Morcillo et al. (2015) reported that maternal depression was related to higher odds of bullying perpetration, with demographic variables controlled. However, this association became nonsignificant once child characteristic variables (e.g., early aggression) were added to the model (Morcillo et al., 2015). In the same study, authors found that parental antisocial behavior was related to higher odds of bullying perpetration. This relation remained significant when other control variables (e.g., child characteristics and maternal depression) were added, except in the final model, where cultural factors were included (Morcillo et al., 2015).

Divorce and Separation. Mixed findings (positive, n = 2; nonsignificant, n = 1) were reported across the three studies examining parental divorce and separation on bullying perpetration. All studies used family structure in analyses, which indicated possible divorce and separation. However, they were conducted in three different cultures, which might explain the discrepant findings. Specifically, in a Taiwanese sample with longitudinal multilevel models (5 waves across 1 year), Wei and Lee (2014) found that living with two married biological parents was negatively associated with later physical bully centrality (i.e., less likely to be nominated as a bully). In a sample of Puerto Rican children living in the US or Puerto Rico with Chi-square tests, Morcillo et al. (2015) found that a higher percentage of children from single-parent families reported bullying perpetration than two-parent families. However, in a predominantly African American sample, Fitzpatrick et al. (2007) reported that alternative family structures (i.e., no biological parents; one biological parent; one biological parent/stepparent) were not significantly associated with bullying perpetration, compared to intact families (i.e., living with two biological parents) via logistic regression with multiple variables controlled (e.g., family violence).

Child Welfare Involvement. The associations between child welfare involvement and bullying perpetration appeared mixed (i.e., positive and nonsignificant) across the two cross-sectional studies. Specifically, Mohapatra et al. (2010) found that child protective services involvement was related to higher odds of bullying perpetration among girls but not boys. However, Edwards and Batlemento (2016) reported that youth in out-of-home placement did not differ significantly from youth in the six home-living arrangements regarding bullying perpetration via the Kruskal–Wallis H test.

Other ACE. Min et al. (2015) reported that neglect was positively related to bullying perpetration in a cross-sectional SEM controlling for physical and emotional abuse.

Associations Between ACEs and Bullying Victimization

There were 36 studies, primarily cross-sectional (cross-sectional, n = 30; longitudinal, n = 6), that investigated the relations of ACEs with bullying victimization. Some studies examined more than one ACE in relation to bullying victimization. For example, CDC (2011) investigated the associations of physical abuse and domestic violence exposure with bullying victimization. This led to the number of associations examined to 58 (i.e., 43 positive, 15 nonsignificant, and 1 negative). Across all ACEs (see Table 3), the cumulative ACE score (i.e., composite ACEs), maltreatment, family violence, neglect, and child welfare involvement were positively associated with bullying victimization across all studies. Physical abuse, emotional abuse, and witnessing domestic violence appeared to be positively associated with bullying victimization as most studies showed positive associations, and the few studies reporting nonsignificant findings could be explained by their methodological features. The associations between the remaining ACEs and bullying victimization were not studied at all or inclusive as the total number of included studies was too small, or the results were split between positive and nonsignificant.

Overall, sample sizes were adequate, with three studies having relatively small samples (N = 129, Knous-Westfall et al., 2012; N = 125, Sterzing et al., 2016; N = 125, Wei & Lee, 2014). Most samples were recruited from schools or communities, except for five samples recruited from special groups, including youth from disadvantaged neighborhoods (Cluver et al., 2010), psychiatric youth (Mustanoja et al., 2011), youth involved with child welfare (Sterzing et al., 2020), sexual minority youth (Sterzing et al., 2016), and youth offenders (Viljoen et al., 2005). The predominant analysis was logistic regression, although other analyses were also used, including Chi-square tests, Kruskal–Wallis H tests, linear regression, multilevel modeling, path analysis, and SEM. Further, the predominant assessment of bullying victimization was self-report, except for three studies that included either parent report (Bowes et al., 2013; Mansbach-Kleinfeld et al., 2015) or peer nomination (Wei & Lee, 2014). Multiple studies used single-item measures (e.g., Mustanoja et al., 2011) or lacked information on measures (e.g., CDC, 2011), although multi-item measures were used in other studies (e.g., Williamson et al., 2018). Lastly, only six of the 36 studies were longitudinal, with one study on each of the following ACEs: abuse (Hong et al., 2017), physical abuse (Bowes et al., 2013), sexual abuse (Hébert et al., 2016), emotional abuse (Calvete et al., 2018), domestic violence exposure (Knous-Westfall et al., 2012), and divorce and separation (Wei & Lee, 2014). Thus, it is unclear across all ACEs how they affect bullying victimization longitudinally, even if they were reported as positively related to bullying victimization above (e.g., family violence).

Composite ACEs. Positive relations between the cumulative ACE scores and bullying victimization were reported in two cross-sectional studies that conducted logistic regression, with gender differences to consider. Specifically, Reisen et al. (2019) found that victims were more likely to report total adversity than non-victims (i.e., OR = 9.8 for 4–10 ACEs, OR = 2.7 for 1–3 ACEs). Forster et al. (2020) reported that an increase from 0 to 6 ACEs was related to higher relational and physical victimization probability in boys and girls, whereas increases in the number of ACEs were associated with increased physical bullying victimization in boys only.

Maltreatment. Positive associations between maltreatment and bullying victimization were reported in two cross-sectional studies with different analyses and definitions of maltreatment. Specifically, G.-F. Wang et al. (2019) conducted logistic regression and reported that maltreatment (i.e., a total score of physical, emotional, and sexual abuse; physical and emotional neglect) was associated with higher odds of being bullied (i.e., physical, verbal, relational and cyber). Holt et al. (2009) found through a Chi-square test that victims were more likely to report maltreatment (i.e., neglect and physical and emotional abuse) than non-victims.

Family Violence. Positive associations between family violence and bullying victimization were reported in two cross-sectional studies with logistic regression. Specifically, Fujikawa et al. (2016) reported in a Japanese sample that family violence was associated with increased odds of being a victim. Lucas et al. (2016) found in a Swedish sample that experience of family violence was related to higher odds of bullying victimization.

Abuse. Overall, abuse seemed to be related to higher concurrent levels of bullying victimization. Three cross-sectional studies reported positive associations and one cross-sectional study reported nonsignificant findings that measured bullying victimization via a single dichotomized item. Longitudinal associations between abuse and bullying victimization were nonsignificant in the only longitudinal study. Specifically, Hong et al., (2018; regression) found that parent abuse (i.e., physical and emotional) was positively associated with direct cyberbullying victimization, as well as indirect victimization. Cluver et al., (2010; regression) suggested that abuse (i.e., physical or sexual) was positively related to bullying victimization. Further, Frías and Finkelhor (2017; logistic regression) reported that abuse (i.e., physical or emotional) was associated with higher odds of being bullied and cyberbullied.

However, Lepistö et al. (2012) reported that family abuse (i.e., physical and emotional) was not related to current bullying victimization. Of note, Lepistö et al. (2012) used a single dichotomized item to measure bullying victimization, whereas the other three aforementioned studies used multi-item measures. Lastly, through longitudinal (3 waves across 2 years) path analysis, Hong et al. (2017) found that parental abuse (i.e., physical and emotional) was not associated with later bullying victimization, either directly or indirectly, via socially withdrawn behavior and deviant peer affiliation.

Neglect. The two cross-sectional studies reported positive associations between neglect and bullying victimization, both with South Korean samples. Specifically, Hong et al. (2018) found via regression that parental neglect was positively associated with direct and indirect cyberbullying victimization. Min et al. (2015) indicated that neglect was related to higher levels of victimization using a SEM with group analyses controlling for emotional and physical abuse.

Physical Abuse. Findings were fairly consistent that physical abuse was associated with higher concurrent bullying victimization, with caveats to consider, such as gender differences and forms of bullying victimization. However, the longitudinal associations between physical abuse and bullying victimization warrant further investigation. Specifically, physical abuse was related to increased odds of bullying victimization in the four cross-sectional studies with logistic regression (CDC, 2011; Lucas et al., 2016; McMahon et al., 2012; Malta et al., 2014). Physical abuse was also positively associated with bullying victimization in five other cross-sectional studies that utilized a variety of analyses, including regression (I. R. de Oliveira et al., 2018), multilevel logistic regression (Azeredo et al., 2015), path analysis (Sterzing et al., 2016; Williamson et al., 2018), and SEM (Min et al., 2015). These nine studies included multiple control variables in analyses, such as demographic variables only (I. R. de Oliveira et al., 2018), domestic violence exposure (CDC, 2011), neglect and emotional abuse (Min et al., 2015), as well as sexual abuse, emotional abuse, and domestic violence exposure (Williamson et al., 2018). These studies also highlight the need to consider gender differences and the various forms of bullying victimization. For instance, Min et al. (2015) reported that physical abuse was positively related to increases in victimization in boys but not girls. Sterzing et al. (2016) found that physical abuse was positively associated with physical bullying victimization but not other forms of victimization (i.e., verbal, relational, or electronic).

A positive relation between physical abuse and bullying victimization was reported in the only longitudinal study. Specifically, Bowes et al. (2013) conducted logistic regression in a longitudinal UK sample and found that chronic bullying victims (i.e., experiencing bullying victimization in both elementary and secondary schools) had increased odds of reporting physical abuse compared to children who were never bullied or only bullied in elementary school.

The last two studies indicated nonsignificant associations between physical abuse and bullying victimization (Mustanoja et al., 2011; Sterzing et al., 2020), both of which conducted cross-sectional logistic regression. Notably, Mustanoja et al. (2011) analyzed a psychiatric youth sample, and Sterzing et al. (2020) examined a female-only sample with half of the participants involved with child welfare, whereas most of the 10 studies mentioned above that reported positive associations utilized school- or community-based samples.

Sexual Abuse. There was no consensus regarding the associations between sexual abuse and bullying victimization, with four studies reporting nonsignificant findings and four studies reporting positive associations. Such heterogeneity could be caused by the different forms of bullying victimizations examined (e.g., Sterzing et al., 2016) or various ACEs controlled in the models. Specifically, Mustanoja et al. (2011) found that sexual abuse was not significantly related to the concurrent odds of bullying victimization in a psychiatric youth sample with physical abuse and witnessing interparental violence controlled. Sexual abuse was also not significantly related to the concurrent odds of bullying victimization in a female-only sample, with half involved with child welfare (Sterzing et al., 2020) and a community sample of youth (Mansbach-Kleinfeld et al., 2015). Lastly, Williamson et al. (2018) found that sexual abuse was not associated with concurrent bullying victimization using a path analysis controlling for multiple ACEs (i.e., domestic violence exposure and emotional and physical abuse).

In contrast, the remaining four studies suggested positive associations. Specifically, bullying victims were more likely to report sexual abuse than non-involved youth (Viljoen et al., 2005; Chi-square test). Holmberg and Hellberg (2010; Chi-square test) found in a female-only sample that girls who had been sexually abused were more likely to report bullying victimization than their non-abused counterparts. Further, Sterzing et al. (2016) found that sexual abuse was positively related to concurrent physical bullying victimization but not other forms of victimization (i.e., verbal, relational, and electronic) in a sexual minority sample with path analysis. It was unclear what confounding variables were included in the model (Sterzing et al., 2016). Lastly, Hébert et al. (2016) reported that sexual abuse was positively associated with later bullying and cyberbullying victimization in a longitudinal study (2 waves across 6 months) with path analysis. However, the study did not control the baseline victimization or any ACEs other than sexual abuse (Hébert et al., 2016).

Emotional Abuse. Overall, emotional abuse was positively associated with bullying victimization. Five of the seven studies reported positive associations with various analyses and control variables, although most studies were cross-sectional. Further, findings highlighted the need to consider the implications of different forms of bullying victimization, culture, and sample characteristics. Specifically, Lucas et al. (2016) reported that emotional abuse was related to increased concurrent odds of bullying victimization. A positive association between emotional abuse and concurrent bullying victimization was also reported by I. R. de Oliveira et al., (2018; regression) and Williamson et al., (2018; path analysis). Further, Sterzing et al., (2016; path analysis) found in a sexual minority youth sample that emotional abuse was positively related to concurrent verbal and electronic bullying victimization but not relational or physical bullying victimization. Lastly, in a longitudinal study (3 waves across 1 year) with SEM, Calvete et al. (2018) found that Time 1 emotional abuse was associated with higher levels of Time 3 bullying victimization via Time 2 rejection schema. These studies included various control variables, such as demographic variables, witnessing domestic violence, and physical abuse (Lucas et al., 2016); demographic variables only (I. R. de Oliveira et al., 2018); witnessing domestic violence, physical abuse, and sexual abuse (Williamson et al., 2018); and Time 1 and Time 2 bullying victimization (Calvete et al., 2018).

The remaining two studies reported nonsignificant associations between emotional abuse and concurrent bullying victimization. Specifically, Sterzing et al. (2020) found that youth with emotional abuse were not more likely to be victims compared to non-involved youth through logistic regression in a female sample, with about half involved with child welfare. The study sample was unique compared to the samples of other studies in this section, most of which were school- or community-based samples. Lastly, Min et al. (2015) reported that emotional abuse was not related to bullying victimization in males or females through SEM group analysis in a South Korean sample with neglect and physical abuse controlled. This sample was recruited in South Korea, whereas most of the remaining studies in this section were conducted in Western countries.

Domestic Violence. It was fairly consistent that witnessing domestic violence was positively related to bullying victimization, as shown in seven of the eight studies, although one study also reported a negative relation based on gender (Mustanoja et al., 2011), and another study reported a nonsignificant association (Le et al., 2017). However, most studies were cross-sectional (n = 6) and utilized logistic regression (n = 5). The findings suggest a need to consider gender differences (Mustanoja et al., 2011), different forms of domestic violence (e.g., psychological vs. physical domestic violence; Frías & Finkelhor, 2017), and bullying victimization (overt vs. relational; Knous-Westfall et al., 2012), as well as the severity of domestic violence exposure (Knous-Westfall et al., 2012).

Specifically, positive associations between witnessing domestic violence and bullying victimization were reported in two cross-sectional studies that conducted logistic regression, with various confounding factors controlled (i.e., physical abuse, CDC, 2011; demographic variables and physical and emotional abuse, Lucas et al., 2016). Further, Mustanoja et al. (2011) suggested that witnessing interparental violence was associated with higher concurrent odds of bullying victimization among boys but decreased odds of victimization among girls in a psychiatric youth sample with physical and sexual abuse controlled. Also, using logistic regression, Frías and Finkelhor (2017) found that witnessing psychological family violence was related to higher odds of being bullied and cyberbullied, whereas witnessing physical violence was not. In addition, Cluver et al. (2010; linear regression) indicated that domestic violence was positively related to bullying victimization in a sample of youth from deprived neighborhoods in South Africa. Further, Williamson et al., (2018; path analysis) reported that witnessing domestic violence was positively associated with bullying victimization directly or indirectly via post-traumatic stress disorder. However, such associations became nonsignificant once physical, sexual, and emotional abuses were controlled.

In a longitudinal study that spanned 6–7 years, Knous-Westfall et al. (2012) found that witnessing severe interparental violence (IPV, defined as injury present) predicted higher rates of later overt bullying victimization but not relational bullying victimization. The positive association between severe IPV and later overt victimization remained significant, even after adding parenting practice variables to the model. Knous-Westfall et al. (2012) also reported that witnessing any type of IPV predicted higher rates of later overt bullying victimization in the entire sample and higher levels of relational victimization in girls only, both of which became nonsignificant after parenting practice variables were controlled. Lastly, Le et al. (2017) followed a sample of Vietnamese youth over 6 months and reported that witnessing IPV was not significantly associated with the odds of being in any subgroups of victims (i.e., stable low, declining, increasing, or stable high).

Divorce and Separation. Mixed findings (positive, n = 3; nonsignificant, n = 3) were reported across the six studies regarding the associations of divorce and separation with bullying victimization. Of note, half of the studies used family structures rather than directly measuring divorce and separation. Most studies were cross-sectional (n = 5) and used simple analyses like logistic regression or Chi-square tests (n = 5). Specifically, Undheim and Sund (2010; Chi-square tests) found that bullying victims reported higher levels of divorce compared to non-involved students. Jablonska and Lindberg (2007) reported that youth from single-father families had increased concurrent odds of bullying victimization, whereas youth from single-mother or shared custody families did not. Further, Azeredo et al., (2015; multilevel logistic regression) indicated that not living with two parents was positively associated with the concurrent risk of bullying victimization compared to living with two parents.

The remaining three studies all suggested nonsignificant associations. Specifically, McMahon et al. (2012) found in a male sample that parental divorce and separation were not associated with the concurrent odds of bullying victimization. Lien and Welander-Vatn (2013) reported that living in a non-two-parent home was not significantly related to the concurrent odds of continuous bullying victimization. Lastly, in the only longitudinal study (5 waves across 1 year), Wei and Lee (2014; multilevel modeling) suggested that living with two married biological parents was not significantly related to victim centrality (i.e., the likelihood of being nominated as a victim of bullying).

Child Welfare Involvement. Positive associations between child welfare involvement and bullying victimization were reported in all three cross-sectional studies from three different countries. Specifically, Edwards and Batlemento (2016) suggested that youth living in out-of-home placements were more likely to report bullying victimization than youth living at home through a Kruskal–Wallis H test in a US sample. Mohapatra et al. (2010) reported in a Canadian sample that family child protective services involvement was associated with higher odds of bullying victimization. Lastly, Long et al. (2017) found in a UK national sample that foster care was related to increased odds of bullying victimization.

Other ACEs. In a US sample with sexual minority youth (N = 125), Sterzing et al. (2016) conducted path analysis and suggested that neither emotional nor physical neglect was related to any forms of bullying victimization (verbal, relational, physical, or electronic).

Associations Between ACEs and Bully-Victim

Nine studies (cross-sectional, n = 8; longitudinal, n = 1) examined the associations of ACEs with being bully-victims. Several studies investigated multiple ACEs in relation to bully-victims. For example, Viljoen et al. (2005) examined the associations of physical abuse, sexual abuse, and family violence with bully-victims. This led to the number of relations examined to 19, among which 13 appeared as positive and six as nonsignificant (see Table 3). Across all ACEs, family violence was positively related to bully-victims across all studies. Physical abuse and domestic violence seemed to be positively associated with bully-victims as most of the studies showed positive results, and the few nonsignificant findings had methodological features that could explain them. The relations of the remaining ACEs with bully-victims were not studied at all or appeared inconclusive due to the small number of included studies, or the results were split between positive and nonsignificant.

Overall, sample sizes appeared adequate, with most samples recruited from schools or communities, except for three samples recruited from special groups, including a psychiatric sample (Mustanoja et al., 2011), youth involved with child welfare (Sterzing et al., 2020), and youth offenders (Viljoen et al., 2005). However, only one of the nine studies was longitudinal (Le et al., 2017). Thus, it is unclear how ACEs are related to bully-victims across time for family violence, domestic violence, and physical abuse, which have concurrent positive associations with bully-victims. Further, all studies used self-report to assess bully-victims, and half of the studies (n = 5) either used single-item measures (Fujikawa et al., 2016; Lucas et al., 2016; Mustanoja et al., 2011) or lacked clarity on bullying measures (CDC, 2011; Sterzing et al., 2020). Lastly, all studies analyzed data via simple strategies (i.e., logistic regression or Chi-square test).

Family Violence. All three cross-sectional studies found positive associations between family violence and bully-victims. Of note, Viljoen et al. (2005) conducted Chi-square tests in a youth offender sample that was predominantly male (79.5%), whereas Fujikawa et al. (2016) and Lucas et al. (2016) conducted logistic regression in school-based samples.

Physical Abuse. Overall, there seemed to be positive concurrent associations between physical abuse and being a bully-victim. Four of the six studies with various control variables suggested positive associations, and the remaining two studies that suggested nonsignificant associations analyzed special samples. However, all studies were cross-sectional and used simple analyses: logistic regression (n = 5) or a Chi-square test (n = 1).

Specifically, physical abuse was associated with higher odds of being bully-victims compared to non-involved groups in three school-based samples (CDC, 2011; Lucas et al., 2016; Yen et al., 2015). These three studies included various covariates, such as age (Yen et al., 2015), witnessing domestic violence (CDC, 2011), as well as emotional abuse, witnessing domestic violence, and demographic variables (Lucas et al., 2016). The association between physical abuse and being bully-victims was moderated by gender, such that girls with physical abuse reported higher odds of bully-victims than boys (Yen et al., 2015). Physical abuse was also related to higher odds of being bully-victims versus pure bullies or victims (Yen et al., 2015). Further, in a sample of youth offenders (79.5% male), Viljoen et al. (2005) found via Chi-square tests that bully-victims were more likely to report physical abuse than non-involved youth.

The remaining two studies suggested nonsignificant associations between physical abuse and being bully-victims utilizing cross-sectional logistic regression (Mustanoja et al., 2011; Sterzing et al., 2020). Of note, Mustanoja et al. (2011) examined a psychiatric youth sample, and Sterzing et al. (2020) analyzed a female sample with half involved with child welfare and lacked clarity on the bullying measures.

Sexual Abuse. The relation between sexual abuse and bully-victims appeared mixed across the three cross-sectional studies (i.e., one positive and two nonsignificant). Specifically, Viljoen et al., (2005; Chi-square tests) found in a sample of youth offenders that bully-victims were more likely to report sexual abuse than non-involved youth. However, sexual abuse was reported as unrelated to the odds of being bully-victims in a psychiatric sample (Mustanoja et al., 2011) or a female sample with half involved with child welfare (Sterzing et al., 2020). Caution should be exercised in interpreting the literature as all three studies used special samples (i.e., youth offenders, psychiatric sample, child welfare involved sample) who likely had additional adversity than sexual abuse.

Emotional Abuse. The association between emotional abuse and bully-victims appeared mixed across the two cross-sectional studies with logistic regression (i.e., one positive and one nonsignificant). Specifically, Lucas et al. (2016) reported in a Swedish school sample (N = 3197) that emotional abuse was related to higher odds of being bully-victims, with several confounding factors controlled (i.e., demographic variables, witnessing domestic violence, and physical abuse). However, Sterzing et al. (2020) found in a US female sample (N = 236) with half involved with child welfare that youth with emotional abuse were not more likely to be bully-victims.

Domestic Violence. Positive relations between witnessing domestic violence and bully-victims were reported in three school samples with various control variables but not in a psychiatric sample. Specifically, in a school sample, Lucas et al. (2016) reported that witnessing domestic violence was associated with higher concurrent odds of being bully-victims, with multiple control variables included (i.e., demographic variables, physical abuse, and emotional abuse). CDC (2011) reported that witnessing domestic violence was associated with higher concurrent odds of being bully-victims, in another school sample with physical abuse controlled. Further, in a short-term longitudinal school sample (2 waves across 6 months) exploring bullying stability, Le et al. (2017) found that youth who reported often witnessing interparental violence (IPV) had increased odds of being in the increasing group of bully-victims, as well as the stable high and stable low groups, but not the decreasing group, compared to youth who did not (or rarely) witness IPV. Lastly, in a psychiatric sample, Mustanoja et al. (2011) reported that witnessing IPV was not associated with the concurrent odds of being bully-victims.

Other ACEs. One study examined the relation between maltreatment and bully-victims. Specifically, G.-F. Wang et al. (2019) reported in a large random cluster sample that maltreatment was related to higher concurrent odds of being bully-victims compared to the non-involved group for various forms of school bullying (i.e., physical, verbal, relational, and cyber).

Associations Between ACEs and General Bullying

One study did not differentiate between bullying perpetration and victimization. Specifically, in a cross-sectional sample of justice-involved youth (73.3% male), Dembo et al. (2021) reported that sexual assault was positively associated with the concurrent odds of bullying behaviors. However, family alcohol problems, drug abuse, and parent incarceration were not related to bullying behaviors.

The Mediating and Moderating Roles of Bullying

Overall, the mediating and moderating effects of bullying on the well-being of youth who experienced ACEs were much less studied than the associations between ACEs and bullying behaviors. However, the limited literature suggests that, in many cases, bullying may further adversely affect youth’s well-being via mediation and moderation.

Bullying Behavior as a Mediator

Mixed (i.e., significant and nonsignificant) results were reported regarding the mediating (or indirect) effects of bullying perpetration and victimization on the association of ACEs with youth well-being outcomes across the four and three studies, respectively. The phrase “mediating effect” was used for longitudinal studies, and “indirect effect” was used for cross-sectional studies. When there were mediating (or indirect) effects, ACEs were related to higher levels of bullying perpetration and victimization, which in turn were associated with negative youth outcomes, except Shamu et al. (2016). Further, the literature suggests possible gender differences in the mediating effects of bullying perpetration and victimization (e.g., Espelage et al., 2014; Min et al., 2015). However, the literature is limited in that many studies did not include three (or more) waves of data or a formal significance test of the mediating effects, and multiple ACEs were not studied.

Bullying Perpetration as a Mediator. Overall, four studies examined multiple ACEs as independent variables (i.e., family violence, neglect, physical abuse, emotional abuse, and combined physical, sexual, and emotional abuse) and youth well-being outcomes as dependent variables (i.e., substance use, intimate partner violence, anxiety, depression, and suicidal ideation). Specifically, in a longitudinal US sample (3 waves across 18 months; N = 1232) with SEM group analyses, Espelage et al. (2014) found that Wave 2 bullying perpetration mediated the association of Wave 1 family violence with Wave 3 youth substance use among boys, but not in girls. Also utilizing SEM, Min et al. (2015) reported in a cross-sectional South Korean sample (N = 1198) that neglect and physical abuse were positively associated with bullying perpetration, which was further positively related to suicidal ideation. Further, the indirect effect of neglect and physical abuse on suicidal ideation was reported as significant. However, it was unclear whether the indirect effect was solely via bullying perpetration or included the effects of delinquency and depressive symptoms (Min et al., 2015). In addition, the authors reported no indirect effect of bullying perpetration on emotional abuse and suicidal ideation (Min et al., 2015).

In a cross-sectional South African sample (N = 3755), Shamu et al. (2016) suggested a potential protective effect of bullying perpetration on youth intimate partner violence. Shamu et al. (2016) found that childhood abuse (i.e., physical, sexual, and emotional) was associated with increased bullying perpetration rates in girls and boys, which were in turn related to decreases in physical and sexual intimate partner violence victimization in girls (b = −0.10) and perpetration in boys (b = −0.081). However, no significant tests of these indirect effects were reported, and the associations between bullying perpetration and intimate partner violence were quite small. Lastly, I. R. de Oliveira et al. (2018) explored the indirect effect of bullying perpetration on the relations of physical and emotional abuse with anxiety and depression in a Brazilian cross-sectional sample (N = 347) via regression and reported it as nonsignificant. Both physical and emotional abuse were positively related to bullying perpetration, but bullying perpetration was not significantly associated with anxiety or depression. Of note, the sample size of I. R. de Oliveira et al. (2018) was much smaller than the three aforementioned studies that suggested possible mediating (or indirect) effects. Additionally, I. R. de Oliveira et al. (2018) recruited participants from schools in areas with high crime rates, whereas the other three studies did not.

Bullying Victimization as a Mediator. The three studies investigated four ACEs (i.e., sexual abuse, physical abuse, emotional abuse, and neglect) as independent variables and multiple youth well-being outcomes as dependent variables (i.e., mental health problems, anxiety, and depression). Specifically, Hébert et al. (2016) reported in a short-term longitudinal study (2 waves across 6 months) that Wave 2 cyberbullying and bullying victimization mediated the association of Wave 1 sexual abuse with Wave 2 youth mental health problems. Min et al. (2015) reported in a cross-sectional sample that bullying victimization had a significant indirect effect on the association between neglect and depressive symptoms in females but not males. Of note, it is unclear whether this indirect effect was solely via bullying victimization or included the effects of delinquency (Min et al., 2015).

Bullying victimization was also reported as having a significant indirect effect on the associations of physical abuse and emotional abuse with depression in I. R. de Oliveira et al., (2018; N = 347) but not in Min et al., (2015; N = 1198). I. R. de Oliveira et al. (2018) utilized regression analysis and a Brazilian sample from schools in high-crime areas, whereas Min et al. (2015) conducted SEM group analysis in a South Korean community sample. Lastly, I. R. de Oliveira et al. (2018) reported a significant indirect effect of bullying victimization in the relation of physical abuse and emotional abuse with anxiety.

Bullying Behavior as a Moderator

Only one study examined bullying behavior as a moderator of the association between ACEs and youth well-being. Specifically, Herba et al. (2008) followed a longitudinal (2 waves across 2 years) Dutch national sample and found that there was a significant interaction between parental internalizing disorder (i.e., a mental health problem) and bullying victimization on youth suicide ideation. When compared to youth who were not involved in bullying, the odds of suicide ideation were increased among youth who were pure victims and whose parents had internalizing disorders but were not increased among youth who were bully-victims and whose parents had internalizing disorders.

Discussion

Research indicates positive associations between some ACEs and bullying behaviors, as well as potential heterogeneity in these associations across ACEs. However, no systematic review has synthesized the literature between all 10 ACEs as examined in the original CDC-Kaiser ACE study and bullying behaviors. The current study provided the first systematic review across two decades (1999–2019) after the CDC-Kaiser ACE study (Felitti et al., 1998), examining the associations of 11 singular ACEs (i.e., 10 ACEs from the CDC-Kaiser ACE study plus child welfare involvement) and their combinations with three subtypes of bullying behaviors (i.e., perpetrators, victims, and bully-victims). This review included 51 empirical studies from 22 countries with various sampling strategies and analyses and adequate sample sizes. The pattern of the findings is surprising in that many ACEs were positively associated with both bullying perpetration and victimization, with a few notable exceptions. Further, there was a tendency for research to focus on perpetrators and victims, with much fewer studies examining bully-victims. Together, the review provides insight into the associations between ACEs and bullying behaviors that may inform future research and practice regarding bullying prevention and intervention.

Associations Between ACEs and Bullying Behavior

This review uncovered strikingly similar patterns of associations of several ACEs with bullying perpetration and victimization. First, composite ACEs, maltreatment, family violence, physical abuse, and domestic violence had positive associations with both bullying perpetration and victimization. Second, sexual abuse, as well as divorce and separation, were not consistently related to either bullying perpetration or victimization. Third, general abuse tended to be positively related to perpetration but not victimization, whereas emotional abuse and child welfare involvement tended to be positively associated with bullying victimization but not perpetration. Fourth, several ACEs from the neglect and household dysfunction categories, either in the form of singular or combined ACEs, were understudied or not studied at all in relation to bullying behaviors.

Prior research indicated potential heterogeneity across ACEs in terms of their associations with bullying behaviors (i.e., some ACEs were positively associated with bullying perpetration, whereas other ACEs were positively related to bullying victimization; Felitti et al., 1998; Hildyard & Wolfe, 2002; McLaughlin et al., 2014). Findings from this review only partially support this notion (i.e., the findings on general abuse, emotional abuse, and child welfare). Of note, several deprivation-related ACEs (e.g., neglect) are understudied (or not studied) in relation to bullying, which could have impacted this review’s capacity to evaluate the heterogeneity across ACEs regarding their relations with bullying behaviors.

The positive associations of the multiple ACEs (i.e., composite ACEs, maltreatment, family violence, physical abuse, and domestic violence) with both bullying perpetration and victimization align with a recent meta-analysis examining the effects of one form of ACEs—namely, exposure to Intimate Partner Violence (IPV)—on bullying behaviors (Lee et al., 2022), which identified similar patterns across bullying perpetration and victimization among individuals exposed to IPV. The current literature focuses on examining the unique effects of individual ACEs, rather than examining them as a collection (e.g., cumulative ACE score), on bullying, which may explain why the patterns are so similar. The effects of risk factors like ACEs often generalize, and ACEs are associated with negative outcomes across multiple domains, including various forms of violence and victimization (Duke et al., 2010). From this perspective, observing similar patterns with both bullying perpetration and victimization is not surprising. ACEs frequently co-occur, and it is typical for adolescents to experience multiple ACEs simultaneously (CDC, 2023). Moreover, some ACEs may be experienced at higher levels earlier in development than later and vice versa. However, studies examining the unique effects of individual ACEs do not provide insight into shared ACEs across the transition from childhood to adolescence. Given that ACEs often co-occur, their cumulative impact across development should be a focal point of future research, encompassing the identification of co-occurring ACE trajectories. These efforts will help understand the mechanisms by which differing ACE profiles relate to bullying behaviors and can inform tailored and targeted intervention efforts.

The findings that sexual abuse, as well as divorce and separation, were not consistently associated with either bullying perpetration and victimization is surprising and inconsistent with the social learning theory (Bandura, 1978) that dysfunctional interactions with caregivers at home may spill over into youth’s peer interactions and increase their likelihood of bullying behaviors. Such findings highlight the need to consider resilience factors that might mitigate the relations between ACEs and bullying (e.g., Positive Childhood Experience [PCE], D. Wang et al., 2021), which could help identify targets for future bullying prevention and intervention programs.

The findings that general abuse was positively related to bullying perpetration (but not victimization), whereas emotional abuse and child welfare involvement were positively associated with bullying victimization (but not perpetration), support the notion that the etiological mechanisms linking ACEs to bullying behaviors may differ across ACEs (e.g., threat- vs. deprivation-related ACEs; Felitti et al., 1998; Hildyard & Wolfe, 2002; McLaughlin et al., 2014). Interestingly, all these three ACEs include some types of threat-related ACEs (i.e., abuse), although child welfare involvement could also indicate deprivation-related ACEs (e.g., a child could be investigated by child protective service due to parental neglect). Findings highlight the need to consider the specific makeup of each ACE profile rather than simply grouping ACEs into threat and deprivation categories when studying their relations with bullying. However, findings on these three ACEs should be interpreted with caution, considering the small number of studies included (e.g., three studies on general abuse and bullying perpetration; and two studies on child welfare and bullying perpetration).

Lastly, bully-victims have received much less attention, in terms of their associations with ACEs, compared to either bullying perpetration or victimization (e.g., 19 analyses vs. 59 and 58 analyses; see Table 3). This is consistent with a recent meta-analysis on intimate partner violence (IPV) exposure and bullying, which also found that bully-victims were understudied (Lee et al., 2022). Among the ACEs that were examined in relation to bully-victims, family violence, physical abuse, and domestic violence were positively associated with bully-victims. Relations with maltreatment, sexual abuse, and emotional abuse were inconclusive due to the limited number of studies included and mixed results. Given their experience with both bullying perpetration and victimization, bully-victims are an important group that warrants further study. In addition, the finding discussed above that multiple ACEs were positively associated with both bullying perpetration and victimization also points to the importance of studying bully-victims in relation to ACEs.

Mediation and Moderation of Bullying

It is too early to make definitive conclusions regarding the mediating or moderating roles of bullying on the associations between ACEs and youth well-being outcomes. The extant literature has documented that bullying experiences have lasting adverse effects on many psychosocial and health outcomes across adolescence (Halliday et al., 2021; Serafini et al., 2023) that are sustained in adulthood (Camodeca & Nava, 2022). Additionally, ACEs and bullying victimization often co-occur, and bullying victimization is considered a new form of ACE in the revised ACE scale (CDC, n.d.; Finkelhor et al., 2012). It is plausible that ACEs cause increases in bullying perpetration and victimization that then lead to changes in psychosocial well-being and health (i.e., mediation). Similarly, the negative associations between ACEs and psychosocial and health outcomes may be exacerbated by bullying behavior (i.e., moderation). Such ideas are consistent with the small literature presented in this review regarding the mediating (e.g., Espelage et al., 2014; Hébert et al., 2016; Min et al., 2015) and moderating (i.e., Herba et al., 2008) effects of bullying behaviors among youth with ACEs. Together, they call for additional research to examine the mediating and moderating roles of bullying.

Implications of the Findings

As schools strive to address challenges around bullying behaviors, they grapple with identifying effective prevention and intervention strategies. The effectiveness of universal school-based bullying prevention programs is weak to modest at best and particularly weak during adolescence (Gaffney et al., 2019; Salmivalli et al., 2021). Further, these programs often fail to reach their primary intended audience—those most victimized or persistent perpetrators (or both), which include youth who experience ACEs. Questions also abound about the extent to which programs can be realistically tailored to meet the diverse needs of students (Salmivalli et al., 2021). Exploring the etiological underpinnings of bullying behaviors, particularly ACEs, can shed light on ways to enhance the effectiveness of school-based bullying prevention and intervention efforts. This review underscores a consistent positive link of several ACEs with bullying perpetration and victimization. It is plausible that adolescents who have those ACEs likely experience the dual role of bully-victims (i.e., both victims and perpetrators of bullying). This overlap between bullying perpetration and victimization complicates the development of effective bullying prevention and intervention strategies.

Prior research has advocated for a concerted effort to identify youth at heightened risk of bullying behaviors to help expedite timely prevention (Jansen et al., 2012). ACE screenings could facilitate early identification of youth who would most likely benefit from targeted bullying prevention and intervention. This approach may increase the effectiveness of these efforts, given that ACEs are robust indicators of bullying behavior, as found in this study. In addition, there are calls for bullying prevention programs to extend programming beyond schools and incorporate families. Such efforts could help parents learn essential skills and start bullying prevention before school entry (Lee et al., 2022; Lereya et al., 2013). The findings from this review on the positive links of multiple ACEs with bullying perpetration and victimization could be utilized by parents for early identification of potential risks of experiencing bullying and providing or seeking timely prevention. Further, findings highlight the need to provide bullying prevention and intervention through the lens of trauma-informed care and avoid retraumatizing these youth (Taylor & Siegfried, 2005) because youth involved with bullying likely also have experienced multiple adverse (or traumatic) experiences.

Limitations and Future Directions

Limitations of the Current Systematic Review

There are several limitations of the current review that need to be considered. First, the findings might be an underestimate of the literature on ACEs and bullying. The review coverage years were 1999–2019. This systematic review is part of a larger search that extracted data from 140 articles and took several years to complete. However, studies have yet to review the associations of the 11 singular ACEs (10 as defined in the CDC-Kaiser study and child welfare involvement) and their combinations with bullying behaviors. Further, this review searched five major databases. However, it is possible that some articles could have been missed if they were not in the five major databases but showed up in others (i.e., Criminal Justice Abstracts). In addition, this review did not include other adverse and traumatic experiences (e.g., community violence).

Second, challenges arose with identifying the definitions of ACEs and bullying for some studies. For example, Fujikawa et al. (2016) measured violence by asking participants, “Have you suffered from violence by adult cohabitants during the past month?” In this case, it was unclear whether youth were the direct target of the violence, witnessed it, or both. This study was classified as family violence to be inclusive. Similar issues were encountered with bullying definitions, particularly among older studies. Fortunately, in 2013, the American Education Research Association’s (AERA) Bullying Task Force released a research report and recommendations for preventing bullying in schools (AERA, 2013). Since then, there has been a concerted effort to conform to a standard definition of bullying that includes repeated nature, power differential (physical or social), and intent to cause harm. Further, the timeframe used to assess ACEs and bullying varied across the studies, such that some measured lifetime and others focused on the past six months. Recollection timeframes are a vital consideration to keep in mind, particularly for longitudinal studies, as well as the importance of measuring ACEs prospectively rather than retrospectively. Additionally, no studies met the inclusion criteria that examined bystander behaviors in relation to ACEs, although “bystander” and “bystanders” were included in the search terms. Bystanders play a vital role in the extent to which bullying behaviors occur. Future reviews may consider broader search terms (e.g., defending behavior) to capture the literature regarding the associations between ACEs and bystander behaviors (e.g., X. Wang et al., 2017).

In addition, this review focused on synthesizing the literature regarding (1) the associations between the 11 ACEs and bullying behaviors and (2) bullying as a mediator and moderator on the well-being of youth with ACEs. Thus, it was outside of the scope of this review to explore in detail the mechanisms by which ACEs are related to bullying behaviors. However, the literature indicates several potential mediators and moderators on the associations between ACEs and bullying behaviors, for example, psychological distress (Sterzing et al., 2016), post-traumatic stress disorder (Williamson et al., 2018), moral disengagement (X. Wang et al., 2017), and social withdrawal (Hong et al., 2017). Future research may explore such mechanisms.

Lastly, the results are presented separately in multiple sections for studies that examined the associations between multiple ACEs and bullying behaviors, which might have drawn unnecessary attention to studies with unique findings. For example, Mustanoja et al. (2011) examined the associations of three ACEs (i.e., physical abuse, sexual abuse, and witnessing IPV) with three bullying behaviors (i.e., perpetrators, victims, and bully-victims). As such, results were presented in nine sections, and eight of the nine effects were nonsignificant. Although this is an extreme example whose nonsignificance may be attributable to the psychiatric sample examined, precautions should be taken to interpret findings from a single study.

Limitations of the Current Literature and Recommendations

While the current review identified consistent positive associations between several ACEs and bullying behaviors, there is a pressing need for further examination on this topic, in particular the understudied (or unstudied) ACEs and the co-occurrence of multiple ACEs in relation to bullying perpetration and victimization, as well as almost all ACEs in relation to bully-victims. In this section, substantive and methodological recommendations for future research are presented.

Adverse Childhood Experiences

Although the existing literature has found positive associations between multiple ACEs and bullying behaviors, albeit some ACEs more than others, much more research is needed. It is somewhat surprising that only a few studies examined composite ACEs (e.g., the cumulative ACE score) in relation to bullying behaviors, considering the frequent co-occurrence of multiple ACEs, as reported in the CDC-Kaiser ACE study. Notably, composite ACEs, while indicating the presence of multiple ACEs, fall short of capturing the severity or identifying the specific collection of ACEs youth experience. Mixture models are a family of person-centered models that allow for examining heterogeneous data patterns and can be leveraged to identify specific ACE combinations over time. Capturing differing patterns of conjoint ACEs across time is essential to examine differential outcomes across developmental transitions (e.g., adolescence to young adulthood).

Research Design and Analyses

Studies varied widely on the type and number of variables that were adjusted, with some studies using univariate approaches that did not adjust for covariates. This variability was addressed by rating the studies and giving more weight to results from multivariate analyses when relevant. For example, the association of family abuse with bullying perpetration was examined using a Chi-square test and logistic regression by Lepistö et al. (2012). It was significant in the Chi-square test but not in the regression analysis with multiple covariates. As such, results were extracted from the regression analysis (vs. the Chi-square test). When interpreting the findings, it is important to consider the within and across study characteristics (e.g., sample, design, analysis, and measurement).

Further, most of the included studies (40 of 51) were cross-sectional. Thus, it is unclear how ACEs affect bullying behaviors across time, although ACEs were conceptualized as predictors of bullying behaviors in this review based on prior research (Bandura, 1978; Pournaghash-Tehrani and Feizabadi, 2009; Whitfield et al., 2003). Longitudinal studies are warranted to further understand the relations between ACEs and bullying behaviors. There is also a pressing need for more advanced multivariate methods. Most studies used Chi-square tests, regression, and manifest path models, which limit the types of research questions that can be examined. Adopting innovative methods and longitudinal designs such as contemporary multivariate longitudinal techniques can uncover novel patterns of ACEs and their relations to changing rates of bullying behaviors across pivotal developmental transitions. Further, recent work to group ACEs into substantive domains could inform how ACEs are conceptualized and modeled longitudinally (Usacheva et al., 2022).

Measurement

The included studies’ measure quality was low overall. It scored the lowest among the 11 items on the quality assessment form, with an average score of 0.82 on a scale of 0–2. Very few articles scored 2 on the measurement item, and multiple articles scored 0 (see Table 2). Regarding bullying, most studies used a dichotomous item to measure both bullying perpetration and victimization. Some studies computed a measure of bullying perpetration or victimization by averaging (or summing) several items, creating a manifest variable. Further, most studies neither measured nor modeled bully-victims, which is problematic given the known co-occurrence of bullying perpetration and victimization and the evidence that bully-victims have worse outcomes than either perpetration or victimization alone (Nansel et al., 2004; Schwartz et al., 2001). In addition, bystander experiences, often captured in a distinct variable, were not included.

Bullying measures need to capture the multifaceted and co-occurring nature of this complex phenomenon. For example, it is plausible that someone could witness a bullying incident and be involved in another as a victim or perpetrator the following week. Bullying behaviors have both persistent (i.e., trait-like) and fluctuating (i.e., state-like) characteristics that span several subtypes (i.e., perpetrators, victims, bully-victims, and bystanders). Bullying measures should not only capture varying levels across multiple sub-domains but also account for change over time, as well as how bullying occurs within a peer network.

Conclusion

The relationship between the 10 ACEs identified in the CDC-Kaiser ACE study (Felitti et al., 1998), child welfare involvement (i.e., another ACE), and bullying behaviors was previously unclear, despite some evidence indicating a positive association between certain ACEs and bullying behaviors. This study conducted the first systematic review of two decades of literature (i.e., 1999–2019) following the CDC-Kaiser ACE study to address this gap. The findings indicate a consistent positive association between various ACEs and both bullying perpetration and victimization, which include composite ACEs, maltreatment, family violence, physical abuse, and domestic violence. However, some ACEs were not consistently related to either bullying perpetration or victimization, and others were positively associated with perpetration or victimization but not both. The research to date has largely overlooked the cumulative impact of multiple co-occurring ACEs on bullying behaviors. In addition, the dual role of adolescents as both perpetrators and victims of bullying (i.e., bully-victims) is understudied in relation to ACEs, as well as the mediating and moderating effects of bullying. Findings highlight the need for longitudinal multivariate research to unpack the complex interplay between ACEs and bullying during adolescence. Ultimately, this review underscores the need for comprehensive ACE screenings and adopting a trauma-informed approach in the development of bullying prevention and intervention efforts.