Objective: To examine the longitudinal association between individual subthreshold symptoms and onset of major depressive disorder (MDD) in adolescence.
Method: Data for analysis come from the Oregon Adolescent Depression Project, a prospective epidemiological study of psychological disorders among adolescents, ages 14 to 18 years, from the general community. A total of 1,709 adolescents completed the initial diagnostic assessments between 1987 and 1989 (T1) and approximately 1 year later (T2), 1,507 adolescents returned for readministration of assessments (88% response).
Results: After controlling for history of depression and gender, seven of the nine DSM-III-R symptoms of depression predicted MDD incidence when tested in separate models. Endorsement of each symptom at T1 increased the likelihood of MDD incidence between T1 and T2. A summary model that included the seven DSM-III-R symptoms as predictors was significant, with sad mood contributing unique variance to the prediction of MDD onset (odds ratio = 2.01).
Conclusions: These findings suggest that much of the variance is shared among symptom predictors and the co-occurrence of symptoms is what constitutes the greatest risk. Moreover, the presence of sad mood contributes additional unique variance to prediction and supports the centrality of depressed mood to MDD.