Maternal depressive symptoms are a crucial risk factor for children’s internalizing problems, though positive mother–child relationships may buffer this risk transmission. Mother–child physiological coregulation (e.g., synchrony) has emerged as a potentially important mechanism of developmental psychopathology and may play a role in the transmission of internalizing symptoms. In this two-wave longitudinal study, we examined whether and how mother–infant physiological synchrony (of respiratory sinus arrhythmia; RSA) moderated the association between maternal postnatal depressive symptoms and children’s internalizing problems in a rural, low-SES community sample (N = 166 dyads). At 6 months, mother–infant RSA synchrony and infant negative affect were assessed during free play. Mother reported their depressive symptoms at 6 months and children’s internalizing problems at 24 months. Multilevel structural equation models indicated that mother–infant dyads demonstrated significant and positive RSA synchrony on average and RSA synchrony significantly moderated the association between maternal depressive symptoms and children’s internalizing problems even after controlling for infant negative affect. Greater maternal depressive symptoms were associated with higher child internalizing problems when RSA synchrony was lower but not when it was higher. This finding suggests that mother–infant RSA synchrony may operate as a resilience factor for the intergenerational transmission of internalizing symptoms in community samples.

Regulatory processes underlie mother-infant interactions and may be disrupted in adverse caregiving environments. Child maltreatment and sleep variability may reflect high-risk caregiving, but it is unknown whether they confer vulnerability for poorer mother–infant parasympathetic coordination. The aim of this study was to examine mother–infant coregulation of respiratory sinus arrhythmia (RSA) in relation to child maltreatment severity and night-to-night sleep variability in 47 low-income mother–infant dyads. Maternal and infant sleep was assessed with actigraphy and daily diaries for 7 nights followed by a mother–infant still-face procedure during which RSA was measured. Higher maltreatment severity was associated with weakened concordance in RSA coregulation related to the coupling of higher mother RSA with lower infant RSA, suggesting greater infant distress and lower maternal support. In addition, higher infant sleep variability was associated with infants’ lower mean RSA and concordance in lagged RSA coregulation such that lower maternal RSA predicted lower infant RSA across the still-face procedure, suggesting interrelated distress. The findings indicate that adverse caregiving environments differentially impact regulatory patterns in mother–infant dyads, which may inform modifiable health-risk behaviors as targets for future intervention.