Introduction

Sex trafficking is one of the fastest growing global criminal enterprises [1], with reported cases in 115 countries [2••]. It is estimated that in 2016, nearly four million adults and one million minors were forced into sexual labor [3]. While exact definitions may vary by country, sex trafficking as defined in the United States (U.S.) refers to the “recruitment, harboring, transportation, provision, or obtaining of a person for the purpose of any commercial sex act where such act is induced by force, fraud or coercion, or when the person induced to perform sex acts is under the age of 18 years” [4]. Sex trafficking has serious consequences to the individual and society [5]. Experiencing sex trafficking has been shown to increase rates of physical illness [e.g., 5] as well as mental health conditions [e.g., 6–8] and can lead to social stigmatization and/or criminalization of trafficked individuals [8]. Sex trafficking also has a significant impact on society, sustaining organized crime, and depriving citizens of basic human rights and feelings of security [9]. Thus, determining methods of identification and prevention are of great importance. As such, this review will provide an overview of recent research (2019 to 2022) in the field of sex trafficking and critically evaluate findings to communicate suggestions for future research and policy work. The review will include a description of the characteristics of sex trafficking cases, risk factors for experiencing sex trafficking, recruitment and maintenance processes, identification and intervention techniques, and treatment approaches. Although the majority of research focuses on trafficked individuals who are under 18 at the time of exploitation, the information described throughout this review includes both child sex trafficking (CST) and adult sex trafficking (AST).

Characteristics of Sex Trafficking Cases

Globally, sexual exploitation (i.e., sex trafficking) is the most common form of human trafficking representing 50% of the cases of trafficked individuals [2••]. While it is estimated that almost five million individuals (adults and children) are trafficked for the purposes of sexual exploitation internationally [3], it is expected that this number has recently increased due to higher levels of unemployment resulting from the COVID-19 pandemic [2••]. Further, the global prevalence of sex trafficking is likely underestimated given the lack of a standardized definition [10, 11] in addition to various individualized (e.g., failing to recognize experiences of victimization, nonreporting due to fear of individuals who perpetrate trafficking or law enforcement) [10, 12, 13] and systematic (e.g., lack of a central database to track occurrences) [14] barriers.

According to the UNDOC [2••], females experience sex trafficking at disproportionate rates, with women and girls, respectively, representing 77% and 72% of the individuals experiencing sexual exploitation. Others have estimated these rates to be even higher with some sources suggesting that up to 99% of sexually trafficked individuals are women and girls [3, 15•]. Most trafficked individuals enter sex trafficking before the age of 18, with the average age of first sex trafficking experience ranging from 12 to 15 years [15•, 16•]. Individuals who identify as part of the LGBTQ + community have twice the odds of being trafficked compared to those who identify as heterosexual [17]. This is hypothesized to be the result of familial discrimination and a lack of available services which increase their chances of experiencing other risk factors (e.g., homelessness) and leads to a higher likelihood of engaging in sex trafficking to meet basic needs [17]. Furthermore, while in lower income countries children are more likely to be trafficked for labor, in high and upper-middle income countries such as those in North America and Europe [2••], children are more likely to be trafficked for sexual purposes. Research also suggests domestic trafficking is more common than international trafficking [18••].

While most trafficked individuals are female, most individuals who perpetrate sex trafficking are male [15•, 19, 20••]. However, recent studies suggest that the prevalence of female individuals who perpetrate sex trafficking may be increasing, with estimates ranging from 16 to 32%. Differences in rates of female individuals who perpetrate sex trafficking may be related to location, as research conducted in the Netherlands identified that individuals who perpetrate sex trafficking internationally are significantly more likely to be female than individuals who perpetrate sex trafficking domestically (21.5% versus 12%) [18••].

The type and size of the sex trafficking organizations may vary based upon several factors. For instance, Veldhuizen-Ochodničanová and colleagues [20••] found that individuals who perpetrate sex trafficking domestically in the U.S. were more likely to work independently and have a single individual they were victimizing while individuals who perpetrate sex trafficking internationally were more likely to work in organized groups and have a larger number of individuals they were victimizing (i.e., over 10). Kragten-Heerdink and colleagues [18••] identified support for these findings in an international context, with individuals who perpetrate sex trafficking internationally reporting victimizing more individuals than those who perpetrate sex trafficking domestically in the Netherlands.

Risk Factors

Numerous factors contribute to the likelihood of being sexually exploited. Several studies have identified risks for experiencing CST in the U.S., including child maltreatment (e.g., prior sexual abuse), involvement in foster care, a history of running away, alcohol and substance use/abuse, poor mental health, justice system involvement, unstable home environments, peer or family influence (e.g., witnessing others engage in sex work), identifying as part of the LGBTQ + community, severe physical disabilities, and/or low cognitive abilities [8, 16•, 17, 19, 21–25]. Similar risk factors have also been reported in Canada and Israel [e.g., 21, 26]. Research comparing domestic and international trafficking suggests that risk factors may differ depending on the context. For example, Kragten-Heerdink and colleagues [18••] found that individuals who were sexually trafficked domestically were more often described as vulnerable due to factors such as age, homelessness, and difficulties in the home (e.g., abuse), whereas those sexually trafficked internationally were more often described as vulnerable because of their disadvantaged background (e.g., poverty and lack of education) and/or a need to provide for others.

Process of Recruitment and Maintenance

One method of improving identification of those being trafficked is through knowledge and recognition of the tactics and processes by which individuals become sexually exploited. Often, individuals have preestablished relationships with those who perpetrate their sex trafficking (e.g., family and friends) and tend to become involved due to economic need [19]. Using a sample of 26 individuals who had experienced sex trafficking in the U.S., Reed and colleagues [27] identified three types of relationships that lead to CST: (1) friends, (2) romantic relationships, and (3) family. For more than half of their sample (54%), friends had influenced involvement in sex work, either through peer pressure or modeling a way to survive/obtain money [27]. Others (31%) had romantic relationships with “boyfriends” who later became pimps, using coercion or violence to force the trafficked individual into sex work and keeping the money for themselves [27]. Familial involvement in sex work was also identified as a pathway towards involvement in CST in 15% of the cases [27]. In another recruitment model developed in the U.S., Roe-Sepowitz [15•] proposed that individuals who perpetrate sex trafficking tend to recruit by targeting vulnerable children (e.g., runaways, those who respond to overtures of romance) and promising money, drugs, alcohol, or a place to stay. The author also noted use of various methods of control such as sexual, physical, and psychological abuse to condition trafficked individuals and prevent them from leaving [15•].

In an effort to synthesize the research on the behaviors and tactics involved in the trafficking process, Winters and colleagues [28••] conducted a review of the literature (including both sex trafficking and child sexual abuse) and proposed the Sexual Grooming Model of Child Sex Trafficking (SGM-CST). According to the SGM-CST, the behaviors and tactics used by individuals who perpetrate sex trafficking can be conceptualized into five stages: (1) victim selection, (2) gaining access and isolation, (3) trust development, (4) desensitization to sexualized content and touch, and (5) postabuse maintenance [28••]. Victim selection involves choosing an individual to traffick based on specific internal and external vulnerabilities (e.g., drug addiction, intellectual deficits, inhospitable home environment, and unmet needs at home). Once the individual perpetrating the sex trafficking has identified a preferred individual, they begin to engage in behaviors aimed at accessing the child, such as manipulating their existing relationships or isolating the child from emotional supports and physical protective factors (e.g., areas with surveillance). The individual perpetrating the sex trafficking then focuses on gaining the trust and cooperation of the individual they are trafficking, as well as others in that individual’s life. This may involve presenting oneself as romantically interested, providing compliments and attention, or utilizing more materialistic tactics such as giving money and gifts. After trust has been established, the individual perpetrating the sex trafficking works to desensitize the youth to sexual content (e.g., asking sexually explicit questions) and contact (e.g., taking explicit photos and exposure to pornography). Lastly, individuals who perpetrate sex trafficking engage in postabuse maintenance to facilitate future abuse and/or prevent disclosure of the abuse. Both emotional manipulation (e.g., competition among trafficked individuals and instilling feelings of shame) and controlling behaviors (e.g., physical abuse, sexual violence, verbal threats, and blackmail) may be used at this stage. This model provides a framework for understanding the recruitment tactics of individuals who perpetrate sex trafficking and could help with prevention through identification, educational efforts, investigations, and prosecution of CST cases. The authors indicate that the next step is validating the SGM-CST using data from trafficked individuals [28••].

International research reveals use of similar methods of recruitment (e.g., through relationships), trust development (e.g., showing attention or gifts), and maintenance (e.g., deception, persuasion, psychological control, and threats) [21, 29]. However, there appears to be some variation by country as studies from Spain and India show recruitment into sexual exploitation may occur as the result of prior engagement in domestic servitude or due to familial obligation. As examples, in Spain and Morocco, young girls from economically disadvantaged families in rural areas are often recruited to work as housemaids for wealthy families and are subsequently targeted by trafficking networks [30], while CST is considered normative among some castes (e.g., Bedia) in India to provide financially for the family [31].

It is also important to consider how these methods may vary depending upon the type of sex trafficking operation. For instance, Veldhuizen-Ochodničanová and colleagues [20••] compared differences between domestic and international sex trafficking processes in the U.S. They found differences in victim selection decisions, in that individuals who perpetrate sex trafficking domestically tended to select minors and individuals who had run away from home, whereas individuals who perpetrate sex trafficking internationally were significantly more likely to target poor, uneducated, or homeless individuals [20••]. In reference to methods of recruitment, they found that individuals who perpetrate sex trafficking domestically and internationally used some approaches at similar rates (e.g., romancing, promising interstate travel, and taking care of money/needs); however, significantly more international trafficking cases involved promises of a job or an American visa [20••]. The researchers also found significant differences in the strategies used to gain and maintain control. Specifically, individuals who perpetrate sex trafficking domestically were more likely to use drug dependence as a method of control, whereas those who perpetrate sex trafficking internationally were more likely to reference smuggling debt, deportation, and ID confiscation in order to maintain compliance [20••]. In a similar comparative analysis conducted in the Netherlands, researchers found differences in the use of violence as a means of coercive control, noting that this method was employed significantly more often by individuals who perpetrate sex trafficking domestically than those who perpetrate sex trafficking internationally [18••]. Overall, these findings suggest that consideration of the country and context (i.e., international versus domestic) is important when looking for indications of victimization.

Identification and Intervention

While research has identified risk factors and recruitment processes involved in sex trafficking, considerably less is known about the extent to which this knowledge has been applied by healthcare professionals, law enforcement, and educators to identify and intervene in cases of sex trafficking. The few studies which have been conducted appear to focus on North American-based professionals.

Screening

Several studies in the U.S. have examined how to improve identification of sex trafficking in healthcare settings. One commonly studied tool is the Short Screen for Child Sex Trafficking (SSCST), a 6-item measure which includes questions relevant to risk factors (e.g., physical violence, running away, sexual history, and substance use) [32•]. Peterson and colleagues [33] examined the use of routine screening for CST using a modified version of the SSCST in emergency departments. They found that the modified SSCST improved specificity when children present with a high-risk chief complaint (e.g., sexual assault, physical assault, and runaway) by increasing CST identification rates from 1.3% to 11.3% during comprehensive follow-up evaluations [33]. Similarly, Hurst and colleagues [34] examined the effectiveness of an electronic self-report version of the SSCST. In a sample of 212 patients, 22 of the 26 patients who had experienced sexual exploitation (84.6%) screened positive for trafficking using the tool. Results suggest that this self-report method was helpful in identifying CST and may be useful in busy clinical environments to ensure additional evaluation services are provided for those who screen positive for CST [34].

Training

In addition to utilizing screening tools, research has highlighted the importance of training professionals who frequently encounter trafficked individuals on identification procedures. Research conducted with service providers (e.g., counselors, medical personnel, law enforcement, and educators) who frequently interact with those who may be experiencing sex trafficking suggests that training can be an effective method of improving identification and access to services.

Service Providers

It appears that many service providers have received at least some training on the identification of CST. To examine the effectiveness of training programs aimed at improving identification of CST, Preble and colleagues [35•] used snowball and purposive sampling targeted at members of antitrafficking networks to survey a range of service providers (e.g., law enforcement, child protective services, and medical personnel; n = 107) in a midwestern state in the U.S. Ninety percent of respondents indicated that they had received training for CST, most often related to the definition of human trafficking, vulnerability factors, and identification of trafficked individuals. However, the authors propose that continued definitional confusion among professionals who had received training may suggest that current methods are not sufficient for improving identification of trafficked individuals [35•].

Awerbuch and colleagues [36] examined the impact of a full-day educational intervention for U.S. professionals working with individuals who may be experiencing CST (e.g., nurses, counselors, police officers, and social workers). They found that the training, which included a description of CST, impacts of screening and identification, an explanation of trauma bonding, and skills for communicating with trafficked individuals, was effective in increasing sex trafficking knowledge among some practitioners [36]. The Commercial Sexual Exploitation of Children (CSEC) is another training manual which has had positive impacts on increasing identification of trafficked individuals in the U.S. [37]. Modules in this program explore (1) an overview of CSEC, (2) pathways and precursors, (3) understanding impacts, (4) victim identification and engagement, (5) effective service delivery, (6) investigating cases, (7) working with cases, and (8) medical and mental health care of trafficked individuals [37]. Kenny and colleagues [37] provided nine three-hour training sessions over the course of six months and found statistically significant differences between pretest and posttest scores on a measure of sex trafficking knowledge. Professionals (e.g., therapists, transportation workers, and social workers) reported that they had a greater ability to identify and recognize trafficked individuals, an improved understanding and knowledge of CST, an increased ability to communicate with and engage trafficked individuals, and a heightened desire to educate others on this problem after receiving the training.

Of note, researchers have identified variations in the definition of sex trafficking as a barrier that impedes identification of trafficked individuals, which may impact the quality and effectiveness of trainings. Preble and colleagues [35•] found that, despite previous training, many respondents indicated confusion regarding definitional aspects of sex trafficking. When examining service providers’ understanding and identification of CST, Gonzalez-Pons [38] found that the persistence of myths related to CST and a lack of definitional understanding interferes with identification of trafficked individuals and service delivery.

Law Enforcement

Trafficked individuals may come in contact with law enforcement due to suspicion regarding the commission of delinquent behavior. Interrogations by police can create mistrust thereby decreasing the likelihood of disclosure and identification [39]. Consequently, research has started to focus on law enforcement responses to sex trafficking. Miller and colleagues [40] examined the effectiveness of the Law Enforcement First Responders Protocol for Commercially Sexually Exploited Children (FRP), a training program that aimed to help law enforcement officers identify those who had been trafficked while avoiding criminalization of these individuals under prostitution laws in the U.S. While overall effectiveness on identification rates was not discussed, the authors note that by encouraging officers to connect trafficked individuals with services rather than criminalize behaviors, the program allowed many trafficked individuals to access important medical services [40].

Other Professionals

Gaps have been identified in that training may not be provided to some professionals who have a high likelihood of interacting with individuals who have been sexually trafficked (e.g., medical providers and educators). For example, although educational and medical societies recommend that students learn to recognize and provide care for sexually trafficked individuals, Talbott and colleagues [41] were able to identify only four programs which aimed to train medical students on identification and intervention. A Canadian study of medical professionals (n = 125) found that 40% of physicians and 51% of other health professionals (e.g., nurses and psychologists) had never received training related to CST and did not feel comfortable making identification judgments [42•]. Further some research suggests that healthcare providers may be more attuned to general signs of child maltreatment rather than having specific knowledge regarding risks of CST [42•, 43].

Similarly, it appears that educators have little guidance on how to identify signs of CST among their students [44]. Chesworth and colleagues [44] proposed a protocol outlining how schools could respond to concerns of CST and help with identification. This included (1) taking action when sex trafficking is disclosed or suspected and reporting even if uncertain, (2) informing and involving relevant personnel, (3) working collaboratively to decide who to include in the report process, (4) submitting a report to Child Protective Services, and (5) following up after the report with the student and family to ensure they are getting proper services.

Treatment

Given the physical and psychological impact of sexual exploitation, once trafficked individuals are identified, clinicians and service providers must work to implement treatment programs that will address the unique needs of this population. Importantly, counselors and mental health workers may need to take on a multifaceted role when working with trafficked individuals, helping to simultaneously address substance use, trauma, family issues, and physical care needs [45]. Cross-culturally, one of the most important factors in making a positive impact when working with trafficked individuals is promoting feelings of safety by communicating acceptance and understanding [46–48]. Other factors that have been found to facilitate treatment engagement include using a harm reduction and trauma-informed lens to understand behavioral patterns, develop trusting relationships, share decision-making responsibilities, and encourage client autonomy by being flexible [46]. To date, no treatment has been developed specifically for individuals who have experienced sex trafficking; however, a variety of approaches developed for those who have gone through other forms of trauma have been examined for use with trafficked individuals.

One approach that has been found to be effective when working with those who have experienced CST is trauma-focused cognitive behavior therapy (TF-CBT) [e.g., 37, 49•]. This manualized treatment builds on cognitive behavioral principles and uses gradual exposure to help youth and caregivers acknowledge and process trauma while learning and applying coping skills [49•]. TF-CBT has been found to result in significant reductions in symptoms of posttraumatic stress disorder, depression, and deviant behaviors and lead to improvements in self-regulation, hope for the future, and positive affect in multiple countries (e.g., the United States [37, 49•, 50], Cambodia [51], and India [52]).

Other treatment approaches include using a mentoring model. My Life My Choice, a U.S.-based treatment program for trafficked youth, pairs youth experiencing CST or those at very high risk of becoming involved in CST with a trained adult mentor who has lived experience with sexual exploitation [53•]. This program has been found to have positive outcomes, improving coping skills and reducing the likelihood of experiencing sex trafficking, engaging in delinquent behavior, and being justice-involved [53•]. Other researchers have found similar support for the inclusion of those with lived trafficking experience in treatment programs [e.g., 54]. Yet, despite the benefits of including individuals with lived experience in the treatment process, they are not typically involved in program development [55].

Conclusions and Recommendations

In recent years, there has been a research focus on better understanding sex trafficking. Empirical data has shown that sex trafficking has become a significant global problem that results in millions of people being sexually exploited each year. While there have been advances in research that shed light on the nature and extent of the problem, there remain many areas in need of further exploration. Below, we detail recommendations for future research and practice.

Recommendations

  1. 1.

    Sex trafficking is increasingly being understood as a unique form of human trafficking. As such, there should be a universal definition for sex trafficking, both domestically and internationally. Currently, there are a wide range of definitions used across different jurisdictions, which may lead to a lack of clarity and impede detection and prosecution. Relatedly, sex trafficking should be defined as a separate construct from human trafficking more generally; for example, the UN defines human trafficking, but does not have a clear definition of what constitutes sex trafficking. Ultimately, universal definitions for sex trafficking can be beneficial in ensuring a common language across jurisdictions thus improving detection, prevention, and research efforts. Having a common definition of sex trafficking would also be beneficial in prosecuting those who perpetrate sex trafficking across jurisdictions and international borders.

  2. 2.

    Sex trafficking is a global issue. As such, information sharing between jurisdictions and across countries should be encouraged by legislators to improve international prevention and identification efforts.

  3. 3.

    Much of the literature on sex trafficking has been conducted in the U.S., with some single studies being conducted in other areas (e.g., Europe and South Asia). Additional research examining the similarities and differences that may exist internationally is needed to adequately identify, prevent, and intervene in cases of sex trafficking. This is especially important since it has been suggested that the perpetrators, tactics, and characteristics of targeted individuals may differ depending on the location, including whether trafficking occurs domestically or internationally [e.g., 18••, 20••].

  4. 4.

    Research on sex trafficking in recent years has largely focused on cases involving minors. More research with adults who have been trafficked is needed to better understand the extent of the problem, as there is some evidence that AST may be more common than CST [3]. Additionally, it would be important to understand how cases of AST and CST may differ, in terms of risk factors for experiencing sex trafficking, recruitment and maintenance tactics, consequences of sex trafficking, and effectiveness of screening, training, and treatment for these populations.

  5. 5.

    There are other subpopulations of trafficked individuals that warrant further examination. For example, individuals from the LGBTQ + community are at an increased risk of experiencing CST [17]; however, literature has focused largely on young, presumably heterosexual, girls. This is especially notable in the treatment literature, as there are a lack of materials and programs designed to address the unmet needs of LGBTQ + trafficked individuals [24, 56]; as such, additional research examining how to best provide treatment for this population is needed.

  6. 6.

    The research regarding training professionals on prevention and intervention tends to focus on health professionals. While medical and mental health professionals have an important role to play in treatment, it is often front-line workers such as school personnel, hospitality workers, transportation workers, and law enforcement officers who have first contact with trafficked individuals and those suspected of being trafficked. Thus, they may have an important role to play in prevention, detection, and prosecution of individuals who perpetrate sex trafficking. For example, research has shown that interviewing styles of law enforcement officers can influence trafficked individuals’ willingness to disclose and provide details about sexual exploitation experiences [39]; as such, training should be tailored to working with this population. Relatedly, policies requiring the training of front-line workers should be implemented to enhance the likelihood of accurate detection and early intervention.

  7. 7.

    Given that vulnerable individuals are often selected by those who perpetrate sex trafficking [15•, 28••], policies advocating for the provision of services (e.g., after school programs, affordable counseling, and work programs) that provide guidance and supervision to at-risk populations should be developed.

In sum, there have been strides to better understand sex trafficking across the globe; however, there remains numerous areas that need further exploration. Additional research is critical, as this will shed light on methods that can be used to identify vulnerable populations, recognize cases of sex trafficking as early as possible, and provide services to those who were sexually trafficked or perpetrated these behaviors.