We utilized three time points of behavioral assessments in a large, population-based birth cohort to examine stability and change in symptoms of psychopathology from childhood into adolescence. Similar to earlier studies, subgroups of psychopathology included four profiles, namely; no problems, internalizing, externalizing and DP [6, 7, 13]. In line with our hypotheses, we observed that externalizing behavior becomes more stable with age, but that the stability of children remaining within the DP subgroup decreases from late childhood into adolescence. Contrary to our hypothesis, internalizing problems did not become increasingly stable with age. Interestingly, the majority (51%) of the children classified in the internalizing subgroup in late childhood progressed to the no problems group in adolescence. Our most notable finding is that, while there is considerable change in behavior for children classified in the DP in childhood, the vast majority (91% of the children) remain in one of the three psychopathology subgroups.
Not surprising, the largest number of children was classified as having no problems across childhood and adolescence. Further, the homotypic continuity observed in this subgroup was 85–88%, meaning that most individuals that do not exhibit psychopathology at an early age, will remain having no psychopathology in adolescence. However, our results also indicate that 5–8% of the children that had no problems in either early or late childhood, transition towards the internalizing group in early childhood or early adolescence, and similarly about 6% transitioned towards the externalizing subgroup. Studying potential underlying mechanisms, including genetic, biological and environmental factors, could ultimately help study and implement prevention strategies targeted on those individuals at-risk.
Together with the work by Basten et al. we show that from late toddlerhood until late childhood the percentage of children included in the internalizing subgroup increases, whereas the rates of children classified in the internalizing subgroup remains stable from late childhood into adolescence [6]. Indeed, studies assessing the age of onset for internalizing disorders find that anxiety disorders, dependent of the subtype of disorder, can emerge at any time during life, whereas the incidence of mood disorders begins to rise during adolescence [15]. However, the median age of onset for specific anxiety and mood disorders is either in early childhood or after early adolescence, with the exception of social phobia. The stable prevalence we observe between late childhood and early adolescence suggests a certain stability in the rate of anxiety symptoms, with fewer children developing internalizing symptoms during this age range. More importantly, in late childhood and early adolescence we found that an increasing proportion of those who transition to the internalizing symptoms subgroup, transitioned either from the externalizing or the DP subgroup at an earlier time point. Thus, these individuals represent a group of children who are already identifiably at-risk, as opposed to those who develop internalizing symptoms after initially having no problems. A future extension of our findings should assess whether intervening to reduce externalizing and DP symptoms can help prevent the later development of internalizing symptoms in those individuals.
We found an increase in the percentage of children with externalizing behavior as these children develop from early childhood into adolescence. This pattern has been observed in earlier work using LPA [7] and it is known that externalizing disorders, such as oppositional defiant disorder and conduct disorder, can develop until late childhood [15, 24, 25]. However, studies have also found a decrease in continuous externalizing symptoms using growth modelling in this age range [26]. While at first glance these results appear contradicting, LTA results obtained in our study as well as in earlier work [7] show that children transitioning to the externalizing subgroup are mainly those who were in the DP at earlier time points. As those in the DP have higher symptoms on all syndrome scales, this increase in individuals in the externalizing subgroup is in line with a decrease in continuous externalizing symptoms. Moreover, those children who transitioned out of the externalizing subgroup, transitioned primarily to the no problems subgroup, which also translates into an overall decrease in externalizing symptoms.
Although a similar pattern for stability within the internalizing and externalizing subgroups was observed earlier, the homotypic continuity we observe is lower than previously reported [7]. Most notably, a larger number of children from the internalizing and externalizing subgroups in early or late childhood transitioned to the no problems group over time, suggesting that for many children symptoms of psychopathology during childhood are a transient phase of development. The differences in homotypic continuity might reflect actual differences between the samples used, but are also likely to be partially dependent on the differences in how psychopathology is reported on the CBCL used here and the Development and Wellbeing Assessment (DAWBA) used in earlier work [27]. Whereas the CBCL is a continuous measure of psychopathology, the DAWBA is a structured clinical interview to diagnose psychopathology. Because of our use of continuous measures, the internalizing and externalizing subgroup consists of children with mostly subclinical symptoms. Possibly, homotypic continuity is higher for those with clinical diagnoses than for those with subclinical symptoms. It would thus be interesting to study whether the initial level of symptoms is predictive of the likelihood that children have persistent problems in a sample enriched for children with subclinical and clinical levels of psychopathology.
Consistent with earlier literature and the conceptualization of the DP, we found that the prevalence of the dysregulation profile is highest in late childhood, after which there is a decline into adolescence [28]. Regarding the development of DP symptoms, we show that those children who already exhibit internalizing or externalizing symptoms are most likely to transition to the DP. However, similar to earlier work, and in line with decreasing prevalence of DP with age, few children transition to the DP after late childhood. Those who are in the DP in early adolescence largely originated from the externalizing and DP subgroups. Notably, the homotypic continuity of the DP decreases between late childhood and early adolescence. Together with the decrease in prevalence, this implies that, for most individuals, psychopathology becomes more clustered within the internalizing or externalizing domain. Despite this decrease in homotypic continuity, our results support the evidence that the DP is an at-risk state for persistent psychopathology, in which the risk of persistence increases with the age at which the DP is exhibited [2, 3, 5]. Where between early and late childhood, 23% of those children that are in the DP transitioned to the no problems group, only 9% of children in the DP transitioned to the no problems group between late childhood and early adolescence. Thus, children exhibiting DP symptoms in late childhood are an optimal target for future intervention studies, as those children are likely to benefit most from early treatment.
The strengths of our study include the large sample size and the longitudinal design embedded within a population-based cohort. Moreover, using data-driven approaches, namely LPA and LTA, we were able to separately measure psychopathology in a more integrated way, compared to assessing individual traits that are likely correlated. Despite these strengths, this study should be considered in light of some limitations. First, we included parental report of child behavior only, other informants (self-report, teacher report) may provide other valuable insights into the development of childhood psychopathology. Unfortunately, we do not have parallel repeated measures of other informants. Second, at T1, the CBCL version 1.5–5 was used, where for those that were older than 5 years of age at assessment, the CBCL version 6–18 would have been more appropriate. At the time of data-collection the decision to use the version 1.5–5 was made to maintain consistency with earlier waves of data-collection not included in the current study. Third, at T2, fit indices provided almost equal support for a four and five profile fit (Supplementary Table 2). However, after visual inspection of the profiles that emerged from our LPA with 5 subgroups, the additional subgroup seemed to be a mix of children with internalizing problems and children with the DP (Supplementary Fig. 1). This was further supported by the results that we obtained from rerunning the LTA with 5 profiles at T2. Most children that were included in the additional fifth profile transitioned to either the internalizing subgroup or the DP at T3 (Supplementary Table 7).
We present both the prevalence and characteristics of psychopathology subgroups and the stability and change that children exhibit in their behavioral development across childhood and adolescence in a large, longitudinal population-based study. Our findings suggest that for many children, internalizing and externalizing problems can be considered a transient phase of development, but that for externalizing problems the predictive value of persistent problems increases with age. Children classified in the DP in late childhood are much more likely to have psychopathology later and the divergence to more specific patterns of psychopathology begins in early adolescence.