Gender differences in the genetic and environmental determinants of adolescent depression.

BACKGROUND The well-documented gender differences in the risk for depression may be explained by genetic factors, by different responses to social context, or by a combination of both. We sought to assess whether there were gender differences in the longitudinal associations between serotonin transporter promoter (5-HTTLPR) genotype and depressive symptoms in adolescents, and whether macrosocial context plays a role in explaining any observed differences. METHODS Using data from a nationally representative survey of adolescents, we applied multilevel mixed models to assess, separately for adolescent males and females (a) the relation between 5-HTTLPR genotype and depressive symptoms and (b) the interaction of county-level deprivation and 5-HTTLPR genotype in models predicting depressive symptoms. All models adjusted for age and other covariates. RESULTS Among females (n=560), main effects models showed an association between the sl genotype and lowered risk of depressive symptoms (b=-.18, P=.03). Among males (n=524), interaction models showed an association between sl genotype and lowered risk of depressive symptoms in deprived counties only (b=-.32, P=.04). CONCLUSIONS In adolescent females, the 5-HTTLPR sl genotype confers protection against depressive symptoms independent of county-level social context, whereas in adolescent males, protection by the same genotype is conferred only within the context of county-level deprivation. Future work should aim to understand how genetic and macrosocial factors jointly shape risk for mental illness, and how these factors shape gender differences in mental illness.