Abstract
<jats:p>Background: The maturation of the autonomic nervous system (ANS) has been suggested to play a crucial role in the development of emotion regulation and later psychosocial functioning. However, longitudinal evidence linking early autonomic development to long-term outcomes remains limited. This longitudinal study investigated the interplay between birth-related factors, early autonomic activity, and psychosocial outcomes across development. Methods: The sample comprised 101 participants followed from two weeks to 14 years of age, with heart rate (HR) and vagally mediated heart rate variability (vmHRV) assessed at 2 weeks, 6 weeks, 3 months, 14 months, and 14 years. Linear models were used to examine associations between birth-related factors and early HR and vmHRV, as well as whether HR and vmHRV trajectories during the first 14 months predicted psychosocial outcomes at 5 and 14 years. Results: Multiple birth-related factors significantly predicted HR and vmHRV at two weeks after birth. Moreover, flatter age-related increases in vmHRV and weaker decreases in HR during infancy predicted higher maternally reported psychosocial difficulties at 14 years in males only, with no such effects at 5 years or in females. Conclusions: These findings underscore the importance of early autonomic maturation in shaping later psychosocial functioning, with effects on adolescent outcomes observed in males only. Early ANS trajectories may represent meaningful predictors of neurodevelopmental outcomes, highlighting their potential relevance for early identification of later psychosocial risk in a sex-specific manner.</jats:p>