Exposure to stress related to the COVID-19 pandemic contributes to psychopathology risk, yet not all children are negatively impacted. The current study examined a parasympathetic biomarker of stress sensitivity, respiratory sinus arrhythmia (RSA), as a moderator of the effects of exposure to pandemic stress on child internalizing and externalizing behaviors in a sample of children experiencing economic marginalization. Three to five years pre-pandemic, when children were preschool-aged, RSA during baseline and a challenging parent-child interaction were collected. Mid-pandemic, between November 2020 and March 2021, children’s exposure to pandemic stress and internalizing and externalizing behaviors were collected. Results demonstrated that children who, pre-pandemic, demonstrated blunted parasympathetic reactivity (i.e., no change in RSA relative to baseline) during the dyadic challenge exhibited elevated risk for externalizing behaviors mid-pandemic. Further, this risk was greatest for children exposed to high and moderate levels of pandemic stress. Consistent with diathesis stress and polyvagal frameworks, these conditional effects suggest that blunted parasympathetic reactivity in response to stress in early childhood may escalate the development of externalizing behaviors following stress exposure at school age.

The COVID-19 pandemic is a unique period of stress, uncertainty, and adversity that will have significant implications for adolescent mental health. Nevertheless, stress and adversity related to COVID-19 may be more consequential for some adolescents’ mental health than for others. We examined whether heart rate variability (HRV) indicated differential susceptibility to mental health difficulties associated with COVID-19 stress and COVID-19 family adversity. Approximately 4 years prior to the pandemic, we assessed resting HRV and HRV reactivity to a well-validated stress paradigm in 87 adolescents. During the pandemic, these adolescents (ages 13–19) reported on their health-related stress and concerns about COVID-19, family adversity related to COVID-19, and their recent emotional problems. The association between COVID-19 stress and emotional problems was significantly stronger for adolescents who previously exhibited higher resting HRV or higher HRV reactivity. For adolescents who exhibited lower resting HRV or HRV augmentation, COVID-19 stress was not associated with emotional problems. Conversely, lower resting HRV indicated vulnerability to the effect of COVID-19 family adversity on emotional problems. Different patterns of parasympathetic functioning may reflect differential susceptibility to the effects of COVID-19 stress versus vulnerability to the effects of COVID-19 family adversity on mental health during the pandemic.

Some Gene × Environment interaction (G×E) research has focused upon single candidate genes, whereas other related work has targeted multiple genes (e.g., polygenic scores). Each approach has informed efforts to identify individuals who are either especially vulnerable to the negative effects of contextual adversity (diathesis stress) or especially susceptible to both positive and negative contextual conditions (differential susceptibility). A critical step in all such molecular G×E research is the selection of genetic variants thought to moderate environmental influences, a subject that has not received a great deal of attention in critiques of G×E research (beyond the observation of small effects of individual genes). Here we conceptually distinguish three phases of G×E work based on the selection of genes presumed to moderate environmental effects and the theoretical basis of such decisions: (a) single candidate genes, (b) composited (multiple) candidate genes, and (c) GWAS-derived polygenic scores. This illustrative, not exhaustive, review makes it clear that implicit or explicit theoretical assumptions inform gene selection in ways that have not been clearly articulated or fully appreciated.