Reciprocal development of depression and self-efficacy in adolescence: A longitudinal twin study.

Depression often emerges during adolescence and can have long-term consequences for mental health. Self-efficacy has been identified as a protective factor, yet little is known about how self-efficacy and depression influence each other over time, independent of genetic and family factors. Data were drawn from 1514 twins (757 twin pairs; 321 monozygotic, 436 dizygotic) from the longitudinal German TwinLife study. Genetically informed longitudinal models were used to examine the reciprocal associations between self-efficacy and depression from age 13 to 15, using both between-family and within-family approaches to account for genetic and shared environmental confounding. Univariate twin models indicated moderate genetic and substantial non-shared environmental contributions to both constructs. A bivariate twin model revealed strong negative genetic correlations between self-efficacy and depression (rA = -0.65 to -0.70) and moderate negative correlations for non-shared environmental influences (rE = -0.33 to -0.40). Between-family cross-lagged panel models showed that higher self-efficacy at age 13 predicted lower depression at age 15 (β = -0.14), and higher depression predicted lower self-efficacy over time (β = -0.13). These reciprocal associations remained in within-family models (βs = -0.12 and -0.13, respectively), indicating that the prospective associations were not explained solely by genetic and shared environmental influences common to twins reared together. Multi-group analyses showed no significant differences in cross-lagged paths between monozygotic and dizygotic twins, suggesting comparable longitudinal associations across groups with different genetic relatedness. These findings suggest that self-efficacy and depressive symptoms are bidirectionally associated from early to middle adolescence, even after accounting for familial confounding.