Pre-pandemic internalized and externalized symptoms predict hair cortisol concentrations in reaction to COVID-19 in girls but not in boys: A longitudinal study

Studies have shown associations between internalized symptoms (IS) and externalized symptoms (ES) and hair cortisol concentrations (HCCs; cumulative cortisol levels) in children. Results are however equivocal with regards to the directionality of the effects (positive vs. negative), and sex seems to moderate the associations. The cross-sectional nature of the studies also prevents to statute on the temporality of these associations. This study aimed to identify the effect of pre-pandemic IS and ES on HCCs in reaction to COVID-19 in youth. In June 2020 (T1), 69 healthy children (M=11.60 y/o, SD=1.55) who visited the laboratory between 2017 and 2019 (T0) provided a 6 cm hair segment corresponding to periods before (Segment A) and during (Segment B) the first wave of COVID-19 in Quebec, Canada. At T0, participants completed the Dominique Interactif to assess IS and ES. A linear regression was conducted, with HCCs percent change between Segment A and B as the dependant variable, IS and ES at T0 and sex as predictors, as well as hair washing frequency and time elapsed between T0 and T1 as covariates. A sex x IS and a sex x ES interactions were revealed. Simple slopes analyses showed a negative association between IS and HCCs [B=-41.266, p=.002] and a positive association between ES and HCCs [B=44.769, p=.004], but only in girls [R(2)=22.6%]. These results suggest that IS and ES symptoms could be used to predict cortisol reactivity to a major stressor in young girls.