Infant Vagal Tone and Maternal Depressive Symptoms: A Bottom-Up Perspective.

Children vary in their susceptibility to environmental exposures such as maternal depression, but little is known about how children shape those same environments. When raising an infant with low arousal, mothers at risk of depression may experience decreased parenting self-efficacy and increased depressive symptoms. We evaluated a longitudinal mediated moderation model that hypothesized interactive effects of infant vagal tone (indexed by respiratory sinus arrhythmia [RSA]) and maternal postpartum depressive (PPD) symptoms on maternal depressive symptoms in early childhood via parenting self-efficacy. Among a sample of 322 very low-income Mexican American mother-infant dyads (46% male infants), infant RSA was assessed at 6 weeks of age; mothers ( = 27.8,  = 6.5) reported PPD symptoms every 3 weeks from 6 weeks to 6 months, parenting self-efficacy at 18 and 24 months, and depressive symptoms at 18 and 36 months. Higher PPD symptoms predicted higher maternal depressive symptoms at 36 months, especially among mothers whose infants had lower resting RSA. The interactive effect of PPD symptoms and infant RSA on 36-month depressive symptoms was partially mediated by lower parenting self-efficacy. Lower infant RSA may exacerbate the detrimental effects of PPD symptoms on subsequent maternal well-being via damage to mothers' beliefs in their ability to parent effectively.