Depression and Personality Traits Across Adolescence-Within-Person Analyses of a Birth Cohort.

Depressive symptoms and personality traits covary in adolescents, but our understanding of the nature of this relation is limited. Whereas a predisposition explanation posits that specific personality traits increase the vulnerability for developing depression, a scar explanation proposes that depression may alter premorbid personality. Attempts to test these explanatory models have relied on analyses that conflate within-person changes and between-person differences, which limits the implications that can be drawn. Moreover, research on the early adolescent years is lacking. The present study therefore examined within-person associations between depressive symptoms and Big Five personality traits across ages 10 to 16. Children (n = 817; 49.9% boys) and parents from two birth cohorts in Trondheim, Norway, were assessed biennially with clinical interviews capturing symptoms of major depressive disorder and dysthymia, and self-reported Big Five personality traits. Analyses were conducted using a random intercept cross-lagged panel model, which accounts for all unmeasured time-invariant confounding effects. Increased Neuroticism predicted an increased number of depressive symptoms-and increased depressive symptoms predicted increased Neuroticism-across ages 10 to 14. Moreover, increased depressive symptoms forecast reduced Extraversion across ages 10 to 16, and reduced Conscientiousness from ages 12 to 14. Increases in Neuroticism may contribute to the development of depressive symptoms-in line with the predisposition model. As regards the scar model, depression may have an even wider impact on personality traits: increasing Neuroticism and reducing Extraversion and Conscientiousness. These effects may already be present in the earliest adolescent years.