Biological sensitivity to the effects of maternal postpartum depressive symptoms on children's behavior problems

The theory of biological sensitivity to context (BSC; Boyce & Ellis, 2005) posits that specific biological characteristics, such as vagal tone, may confer risk for physical and mental health outcomes for some children but promote health for others. High levels of resting respiratory sinus arrhythmia (RSA), an index of vagal tone, may confer susceptibility to the effects of the caregiving environment on child development. Consistent with BSC, I expected that, relative to infants with lower RSA, infants with higher RSA would demonstrate fewer behavior problems if their mothers reported fewer postpartum depressive symptoms, but more behavior problems if their mothers reported more postpartum depressive symptoms. I also evaluated whether observed child social engagement with their mothers mediated children's biological sensitivity to the effects of postpartum depressive symptoms on behavior problems in early childhood. I evaluated a mediated moderation model among a sample of 322 low-income Mexican American mother-infant dyads. As expected, the RSA x maternal depressive symptoms interaction, controlling for covariates, was a significant predictor of internalizing, externalizing and total behavior problems, and high vagal tone conferred susceptibility for externalizing behavior problems. Contrary to my hypothesis, children with low RSA may be more susceptible to the effects of maternal postpartum depressive symptoms on children's internalizing and total behavior problems, and child social engagement did not account for these effects. Among infants in economically disadvantaged families, lower RSA and fewer maternal depressive symptoms may promote resilience, and more research is needed to understand behavioral mediators of biological sensitivity.