EARLY VULNERABILITY AND ACUTE STRESS RESPONSES IN CHILDHOOD

This study examined individual differences in early-vulnerability using a person-centered approach, integrating parental and child characteristics with circadian activity and acute stress response of young children. Participants were 198 children aged 7-8 years from the ABCD community cohort in Sabadell. Saliva samples were collected for 2days during a weekend to evaluate circadian rhythms (including the cortisol awakening response-CAR) and diurnal slope. Children completed the Trier Social Stress Test (TSST), during which saliva samples were obtained to measure cortisol, alpha-amylase (sAA) and subjective stress responses (measured using the Self-Assessment Manikin, SAM). Hair samples were collected to assess accumulated cortisol. Parents completed questionnaires assessing their own perceived stress, anxiety, depressive symptoms and life-events, as well as their children’s life-events, temperament, mental health and aggressive behavior. A principal component analysis identified three latent psychological dimensions: parent vulnerability, child vulnerability, and life-events. Unsupervised clustering based on these components yielded two groups characterized by high versus low-vulnerability. Girls showed higher circadian sAA levels. High-vulnerability children exhibited a flatter CAR and diurnal cortisol slope. The TSST elicited subjective and physiological responses, girls showing greater cortisol and sAA reactivity. In contrast, boys exhibited higher hair cortisol levels. Preliminary piecewise multilevel linear-mixed model indicated, only in boys, elevated sAA and a trend toward reduced cortisol reactivity in vulnerable children. Vulnerable children also showed higher TSST-associated subjective stress and increased hair cortisol, particularly among boys. These data suggest that early vulnerability induces differences in circadian patterns and stress responses of biomarkers in a community sample of young children