Background: Cortisol is a hormone released by the hypothalamic-pituitary-adrenal axis (HPA axis) and is involved in sustained response to stressful stimuli as well as maintaining several other body processes. Salivary cortisol is implicated in physiological reactions to psychosocial stress and is an indicator of HPA dysregulation. In this study, we sought to estimate genetic and environmental influences on salivary cortisol response to a psychosocial stressor.
Methods: Participants include 112 monozygotic and 158 dizygotic Caucasian adolescent and young adults twin pairs (Mean age= 16.8, SD=1.3; 55% female) who participated in a Trier Social Stress Test, a well validated cortisol provocation task. Salivary cortisol samples were collected at four time points after completion of the task: immediately after concluding the task, and every 15 minutes following. Area under the curve (AUC) was calculated for each twin; this approach is based on repeated salivary cortisol measurements to generate a response profile that captures the overall cortisol response and rate of change over time. A univariate biometrical model was used to estimate additive genetic, common (shared) environment, and unique (non-shared) environmental contributions to cortisol response to psychosocial stress.
Results: MZ correlations for salivary cortisol were significant, r= .49, and DZ twins were also significantly correlated at r= .17. AUC cortisol response was moderately heritable (h2= .47) with remaining variance accounted for by unique, non-shared environment. No significant influence of the shared environment was observed.
Conclusions: Cortisol response to a psychosocial stressor was moderately heritable. This study is the first to examine the heritability of AUC salivary cortisol response to a psychosocial stressor in an adolescent and young adult sample. Results suggest moderate genetic influences in adolescents and young adults. Future studies should seek to determine the stability of heritability as a function of aging and exposure to environmental stressors.
