Abstract
<p>Parental internalizing symptoms are a risk factor for the development of adolescent depressive symptoms, potentially through disruptions in stress systems. This longitudinal, preregistered study followed Dutch adolescents (N = 497, 56% boys, Mage T1 = 13.03, SD = 0.46) and their parents (495 mothers, Mage T1 = 44.41, SD = 4.45; 446 fathers, Mage T1 = 46.74, SD = 5.10) across six years. Parents and adolescents reported their own internalizing symptoms annually. At age 17.5, adolescents completed a standardized stress task to assess cortisol reactivity. Higher maternal internalizing symptoms predicted higher adolescent depressive symptoms at age 18 (β = .23, p &lt; .001); however, this effect was no longer significant after adjusting for adolescents’ prior depressive symptoms. Neither maternal nor paternal internalizing symptoms predicted cortisol reactivity in middle to late adolescence, nor did adolescent cortisol reactivity predict depressive symptoms in late adolescence. These findings provide valuable insight for specifying the developmental windows for the intergenerational transmission of depressive symptoms and the role of HPA axis reactivity. Future studies should consider broader developmental windows and multi-method assessments.</p>