Abstract
BACKGROUND: Group-based trajectory modeling holds promise for the study of prognostic indicators in the mood disorders because the courses that the individuals with these disorders follow are so highly variable. However, trajectory analyses of major depressive disorder have so far not included some of the more robust predictors of mood disorder outcome, nor have they described interactions between these predictors. METHODS: A group of 186 individuals aged 15-20 years with past or current depressive symptoms, who had recently begun taking a serotonin reuptake inhibitors antidepressant, underwent extensive baseline evaluations and were then followed for up to 2 years. Trajectory analyses used weekly ratings of depressive symptoms and the resulting groups were compared by the risk factors of sex, psychiatric comorbidity, negative emotionality, and childhood adversity. RESULTS: A three-group solution provided the best statistical fit to the 2-year symptom trajectory. Negative emotionality and childhood adversity, though correlated, independently predicted membership in higher-morbidity groups. Female sex and comorbidity with generalized anxiety disorder (GAD) were also significantly more likely in the trajectory groups with higher symptom levels. However, the presence of GAD, rather than female sex, was the most important determinant of group membership. Negative emotionality was predictive of group membership only among women. CONCLUSIONS: Trajectory analyses indicated that week-to-week variations in depressive symptoms across individuals could best be condensed into low, remitting and persistent symptom patterns. Female sex, anxiety symptoms, negative emotionality and childhood adversity were each independently associated with trajectories of higher morbidity but negative emotionality may be prognostically important only among women.