The Effect of an Intervention Teaching Adolescents that People can Change on Depressive Symptoms, Cognitive Schemas, and Hypothalamic-Pituitary-Adrenal Axis Hormones.

Interest is increasing in developing universal interventions to prevent depression in adolescents that are brief enough to be scaled up. The aim of this study was to test the effects on depressive symptoms, cognitive schemas, and Hypothalamic-Pituitary-Adrenal Axis Hormones of an intervention focused on teaching an element of an incremental theory of personality, namely, the belief that people can change. We also examined whether grade level moderated the effects of the intervention. A double-blind, randomized, controlled trial was conducted with 867 Spanish adolescent participants (51.9% boys, Grades 8-10) randomly assigned to an incremental theory intervention (n = 456) or an educational control intervention (n = 411). The adolescents completed measures of depressive symptoms and negative cognitive schemas at pretest, at 6-month follow-up, and at 12-month follow-up. A subsample of 503 adolescents provided salivary samples for cortisol and DHEA-S testing. In 8th grade, adolescents who received the incremental theory intervention displayed a greater decrease in depressive symptoms and cognitive schemas and a lower increase in DHEA-S. Moreover, in adolescents who received the intervention, the rate of adolescents with high depression scores decreased by almost 18% whereas in the control group, the rate increased by 37%. Surprisingly, the effects of the intervention were in the opposite direction among adolescents in 9th grade. These data indicate that a brief universal intervention could prevent depressive symptoms under some conditions, but developmental characteristics can moderate the effectiveness of this approach.