The implications of sympathetic and parasympathetic regulatory coordination for understanding child adjustment.

The autonomic nervous system (ANS) is comprised of sympathetic and parasympathetic branches that control core adaptive systems, including cardiac regulation, across periods of rest, reactivity, and recovery. Despite their heavily intertwined functions, research examining the coordination of parasympathetic and sympathetic ANS regulation is limited. This study examined the effects of 6-year-olds' (N = 198; 49.5% female; 46% Latinx) capacity for ANS reactivity and recovery in both sympathetic (i.e., pre-ejection period [PEP]) and parasympathetic (i.e., respiratory sinus arrhythmia [RSA]) systems on their caregiver- and examiner-reported adaptability and attention problems at age 8. Results indicated that children's later adaptation was better accounted for by the coordination of their PEP and RSA activity than by either system in isolation. Children who evidenced optimal reactivity and recovery patterns, which entail reciprocal sympathetic and parasympathetic activity, evidenced more adaptability and fewer attention problems at age 8. In contrast, children who displayed discoordinated ANS reactivity patterns (e.g., high activation of both systems) or a total failure to recover (e.g., short PEP connoting high sympathetic activity and low RSA connoting low parasympathetic activity) evidenced poorer adjustment. These findings illustrate the incremental knowledge afforded by the joint consideration of both sympathetic and parasympathetic branches of ANS regulation in concert, as well as the importance of considering both ANS reactivity and recovery capacities for understanding adaptation.