In this study, we assessed parent- and child-reported internalizing problems in children and adolescents aged 8 to 18 years before the first Dutch COVID-19 pandemic lockdown, during the first peak/Dutch lockdown (Apr–May 2020), and during the second peak/Dutch partial lockdown (Nov–Dec. 2020) in two general population cohorts and two clinical cohorts. In the general population, we found that internalizing problems were higher during the first peak of the pandemic compared to pre-pandemic based on both child and parent reports. Yet, over the course of the pandemic, on both child and parent reports, we observed similar or even lower levels of internalizing problems. Children in the clinical population reported higher levels of internalizing symptoms over the course of the pandemic, while parents did not report differences in internalizing symptoms from pre-pandemic to the first peak of the pandemic nor over the course of the pandemic.
Our findings in the general population, of higher levels of internalizing problems during the first peak compared to pre-pandemic, are in line with prior research [6,7,8, 11,12,13]. At the start of the first pandemic peak, both children and adults were subjected to significant changes in their psychosocial environment due to the implementation of social distancing measures. Given that social interactions are fundamental to a healthy development in children and adolescents [1, 2], the sudden social deprivation and changes in daily routines as introduced by lockdown (e.g., closure of schools and social/sports clubs) may have contributed to the observed higher levels of depressive symptoms and anxiety at the start of the pandemic, as reported in this study by both parents and children themselves. Our finding that levels of internalizing problems did not differ or were lower over the course of the pandemic is in line with another study showing that anxiety and depressive symptoms subsided in adolescents of the general population in the four months after the first peak of the pandemic [25]. Specifically, concerns about home confinement and school (e.g. transitioning to online learning) have been shown to be strongly associated with increased anxiety and depressive symptoms since the onset of the pandemic [25]. Therefore, the relaxation of home confinement measures after the first peak of the pandemic and habituation to the new online school environment may have contributed to our finding that levels of anxiety and depressive symptoms did not differ or were lower over the course of the pandemic in children and adolescents of the general population.
In the clinical population, we saw higher levels of child-reported internalizing problems over the course of the pandemic. Literature indicates that children in clinical populations overall have less resilience than children without pre-existing mental health problems [26]. Resilience represents the capacity to quickly adapt to adversity, and being less resilient has been associated with worse physical, mental and emotional functioning [27]. As such, children with pre-existing problems may experience more difficulties as the pandemic continued. Furthermore, children in clinical populations may have experienced a change in treatment quality during times of the pandemic, due to increased demands on mental health services, which may have led again to an exacerbation of their internalizing problems [28]. In contrast, parents of children from the clinical population did not report any differences in their children’s internalizing problems from pre-pandemic to the first peak of the pandemic nor over the course of the pandemic. These results could indicate that the changes in their children’s mental health (as reported by the children themselves) are less noticed by the parents of children with pre-existing problems. For example, earlier studies have shown that in families of child mental health patients, family routines and functioning are already substantially accommodated to the needs of the child [29, 30], whereby a stressful life change, such as the pandemic —from a parent’s perspective— may not have introduced changes significant enough to considerably alter their perception of their child’s functioning. Also, previous studies have shown that internalizing problems —in contrast to externalizing problems— may be less readily noticed by parents [34, 35]. This may result in greater rater discrepancies, especially in vulnerable populations. Another explanation could be that, parents of children with pre-existing problems may perceive changes in their child’s mental health as less problematic, knowing that newly arising problematics will be promptly addressed within the framework of their child’s ongoing youth/psychiatric care. However, a possible ceiling effect could also explain our results, as parent-reported internalizing problems for the clinical population were already high before the pandemic, and the parental questionnaire (BPM) may not have been sensitive enough to capture increases in internalizing problems during the pandemic.
Whereas in the clinical cohort, we saw higher levels of internalizing problems as the pandemic continued, this pattern stands in contrast to the similar or lower levels of internalizing problems we found in the general population cohorts over the course of the pandemic. Specifically, given that child mental health patients may have a different psychosocial environment than children of the general population [29], the changes in government regulations throughout the pandemic (during our Nov–Dec pandemic measurement), such as re-opening of schools and social/sports clubs, may have favorably affected children of the general population but to a lesser extent the clinical populations. For example, more contact with peers may have contributed to fewer internalizing problems for children of the general population, whereas for children of clinical populations such peer contact may at baseline be more compromised (e.g., mental health problems may interfere with psychosocial functioning) or may not represent a correlate of improved mental health (e.g., school/peer group settings may perpetuate anxiety problems). Thus, the differences in the social environment/psychosocial functioning in these two populations may have amplified divergence in internalizing problems in these two populations over the course of the pandemic.
Some limitations of the present study need to be addressed. First, child reports in the clinical cohort before the pandemic were missing, and as such no inferences can be made of how great the initial impact of the pandemic was as experienced by children in this population. Moreover, none of the samples had collected data at all measurements on both parent and child reports, and representativeness of the samples could not be checked except for the general population cohort (KLIK). Families participating in the NTR generally show high socioeconomic status [16], which may have resulted in a slight overestimation of differences between clinical and population samples, in line with literature showing that children and adolescents of families with higher socioeconomic status experienced fewer emotional and behavioral problems in stressful life situations [31]. However, since we compared internalizing problems at the various time points for each sample separately, not controlling for sociodemographic differences may only have impacted generalizability. Furthermore, the mean age of children in the pre-pandemic and especially pandemic sample of the NTR is lower (childhood age range) than the mean age of the other samples (adolescent age range). In line with literature indicating that the COVID-19 pandemic may have especially perpetuated adolescents’ internalizing problems [25, 32], the NTR sample in our present study may as such have exhibited comparably smaller differences in internalizing problems before versus during the pandemic. Lastly, the samples at the various measurements in the separate cohorts are independent, so no inferences about within-person changes in internalizing behavior over time could be made, calling for future longitudinal research to address this.
The present study also has several strengths. We included large samples with children from both the general and clinical population and collected both parent and child reports. Also, the male-to-female ratio in our clinical samples is representative of the male-to-female ratio of the total population of the four Dutch psychiatric centers that were included in this study, thereby increasing generalizability of our results. Furthermore, we were able to compare the data that were collected during the pandemic with data that were collected yearly from 1995 until 2019. These yearly measurements show that proportions of elevated internalizing problems in the general population ranged from 5.6 to 8.8% between 1995 and 2019, confirming that the proportions reached during the pandemic in the general population (13.0–16.6%) represent unusually elevated problems, rather than random fluctuations in proportions of internalizing problems (see Fig. 2).
In summary, our results show that in the general population levels of internalizing problems are higher since the start of the pandemic and that more children report elevated levels of internalizing problems and may require additional support. In the clinical sample, we found that levels of child- (but not parent-) reported internalizing problems were higher over the course of the pandemic. Overall, the findings indicate that children and adolescents from both the general and clinical population were affected negatively by the pandemic in terms of their internalizing problems. Attention is therefore warranted to investigate what long-term effects this may cause and to monitor if internalizing problems return to pre-pandemic levels or if they remain elevated post-pandemic. These insights, combined with future multi-informant and longitudinal research in children of both general and clinical populations, may provide relevant information for policy-makers and mental health prevention and intervention services in times of the COVID-19 or potential future pandemics.