Infant 6-Month Psychophysiology During Interaction With Mother Is Differentiated by 12-Month Attachment Quality

Infant-mother attachment relationships play a crucial role in shaping children's psychological and physiological well-being. This study examined whether attachment quality at 12 months is associated with infant psychophysiological responses to mild stress at 6 months. Participants were 222 ethnically and socioeconomically diverse mother-infant dyads followed from the third trimester of pregnancy through the infant's first year. At 6 months, dyads participated in a free play session followed by the Face-to-Face Still-Face Paradigm (FFSFP). Infant saliva samples were collected before and after free play and at 1, 20, and 30 min post-FFSFP to measure oxytocin, cortisol, and salivary α-amylase (sAA), biomarkers associated with stress and social regulation. Maternal blood samples were collected at 10, 20, and 30 min post-FFSFP and analyzed for oxytocin and cortisol. Attachment quality was assessed at 12 months using the Ainsworth Strange Situation Paradigm. Linear mixed-effects models showed that securely attached infants had significantly higher oxytocin and lower sAA levels than insecurely attached infants, with sAA decreasing over time only in the secure group. No significant differences emerged in infant cortisol reactivity or maternal hormone levels. Findings suggest a potential link between infant attachment quality and stress regulation, particularly involving oxytocin and sympathetic nervous system activity.