This study examines the integration of the two main branches of the stress response system: the autonomic nervous system (via salivary alpha-amylase, sAA) and the hypothalamic-pituitary-adrenal axis (via cortisol). Mothers (n = 117) were randomized to have either a positive (n = 57) or conflictual (n = 60) discussion with their marital partner, after which mothers and infants (Mage = 5.9 months) engaged in free-play, followed by an infant-focused challenge task. Saliva samples were collected from the mother to assess physiological reactivity and recovery to the marital discussion, and from the infant to assess physiological reactivity and recovery to the challenge task. For both mothers and infants, sAA - cortisol coordination varied across the respective tasks. Further, findings suggest the sAA - cortisol connection is under social control, with stress response system coordination occurring only in supportive social relationships (i.e., mothers experiencing cohesive marital discussions, and in infants with sensitive and responsive mothers). Interestingly, however, it appears social support might function differently in mothers vs infants. Findings advance our understanding of the complex integration of stress physiology in the context of social relationships.
