Sleep Duration and Depressive Symptoms: A Gene-Environment Interaction

Objective: We used quantitative genetic models to assess whether sleep duration modifies genetic and environmental influences on depressive symptoms. Method: Participants were 1,788 adult twins from 894 same-sex twin pairs (192 male and 412 female monozygotic [MZ] pairs, and 81 male and 209 female dizygotic [DZ] pairs] from the University of Washington Twin Registry. Participants self-reported habitual sleep duration and depressive symptoms. Data were analyzed using quantitative genetic interaction models, which allowed the magnitude of additive genetic, shared environmental, and non-shared environmental influences on depressive symptoms to vary with sleep duration. Results: Within MZ twin pairs, the twin who reported longer sleep duration reported fewer depressive symptoms (e(c) = -0.17, SE = 0.06, P < 0.05). There was a significant gene x sleep duration interaction effect on depressive symptoms (a'(c) = 0.23, SE = 0.08, P < 0.05), with the interaction occurring on genetic influences that are common to both sleep duration and depressive symptoms. Among individuals with sleep duration within the normal range (7-8.9 h/night), the total heritability (h(2)) of depressive symptoms was approximately 27%. However, among individuals with sleep duration within the low (< 7 h/night) or high (>= 9 h/night) range, increased genetic influence on depressive symptoms was observed, particularly at sleep duration extremes (5 h/night: h(2) = 53%; 10 h/night: h(2) = 49%). Conclusion: Genetic contributions to depressive symptoms increase at both short and long sleep durations.