Maternal internalizing (anxiety and depressive) symptoms are a robust risk factor for the development of internalizing symptoms in offspring, yet the neurobiological mechanisms that influence this association remain relatively unexplored. The aperiodic “slope” of the EEG power spectrum (i.e., aperiodic exponent) is hypothesized to index the cortical excitatory-inhibitory balance and may serve as an early neurophysiological marker of mental health risk. In a prospective longitudinal cohort (N = 323 mother–child dyads), we examined associations among maternal anxiety and depressive symptoms in infancy and at age 5 years, child EEG aperiodic slope at age 3 years, and child internalizing symptoms at age 5 years. We investigated whether the aperiodic slope at 3 years (a) mediated associations between maternal internalizing symptoms in infancy and child internalizing symptoms at age 5 years and/or (b) moderated associations between maternal internalizing symptoms and child internalizing symptoms at age 5 years. There were no significant mediation effects. The aperiodic slope moderated the association between maternal anxiety symptoms and child internalizing symptoms: A steeper slope was associated with a stronger association between maternal and child symptoms. Findings suggest that the EEG aperiodic slope may represent a moderator of intergenerational risk for internalizing symptoms in early childhood.
