Abstract
BACKGROUND: The course of depression is heterogeneous. The employed treatment is a key element in the impact of the course of depression over the time. However, there is currently a gap of knowledge about the trajectories per treatment and related baseline factors. We aimed to identify trajectories of depressive symptoms and associated baseline characteristics for two treatment arms in a randomized clinical trial: treatment as usual (TAU) or TAU plus transdiagnostic group cognitive behavioral therapy (TAU + TDG-CBT). METHODS: Growth mixture modeling (GMM) was used to identify trajectories of depressive symptoms over 12 months post-treatment. Logistic regression models were used to examine associations between baseline characteristics and trajectory class membership in 483 patients (TAU: 231; TAU + TDG-CBT: 251). RESULTS: We identified different patterns of symptom change in the randomized groups: two trajectories in TAU ('improvement' (71.4%) and 'no improvement' (28.6%)), and four trajectories in TAU + TDG-CBT ('recovery' (69.8%), 'late recovery' (5.95%), 'chronicity' (4.77%), and 'relapse' (19.44%)). Higher baseline symptom severity and comorbidity were associated with poorer treatment outcomes in both treatment groups and worse emotional regulation strategies were linked to the 'no improvement trajectory' in TAU. The TAU + TDG-CBT group demonstrated greater symptom reduction compared to TAU alone. CONCLUSIONS: There is heterogeneity in treatment outcomes. Integration of TDG-CBT with TAU significantly improves symptom reduction compared to TAU alone. Patients with higher baseline severity and comorbidities show poorer outcomes. Identification of trajectories and related factors could assist clinicians in tailoring treatment strategies to optimize outcomes, particularly for patients with a worse prognosis.