Trajectories of internalizing problems during and after the COVID-19 pandemic: The effects of sex and early life stress.

The COVID-19 pandemic and its associated lockdowns had a detrimental impact on adolescent mental health, exacerbating levels of emotional difficulties that were already increasing in this population. The course of these difficulties after lockdown protocols ended, however, is not fully understood. Further, the effects of early life stress (ELS) and biological sex on mental health during and following the pandemic are also not clear. This study leverages data from a longitudinal project examining adolescent mental health that predates the pandemic. Internalizing problems were assessed in 222 children (58.6% females) ages 9-13 years at recruitment (baseline; 2013-2016) and at four more timepoints, each approximately two years apart. Participants also completed an interview assessing ELS at baseline. We assessed internalizing problems across each phase of the pandemic (i.e., pre-COVID, during the COVID lockdown, after reopening) as a function of ELS and biological sex. We found that whereas unpredictability-related ELS was associated with internalizing problems in girls across all COVID phases, the association between threat-related ELS and internalizing problems from pre-lockdown to post-reopening decreased in girls and increased in boys. Further, threat-related ELS was associated with post-reopening internalizing problems in boys through lower adaptability. Sensitivity analysis showed that the attenuation of the threat-internalizing association in girls and strengthening of the association in boys was not due to aging. Collectively, these findings suggest that there are sex- and ELS-specific changes in psychological functioning in relation to the pandemic. Further research is needed to better understand mechanisms that foster risk or resilience following stress exposure.