Behavioral Activation Contributed to the Total Reduction of Depression Symptoms in the Smartphone-based Cognitive...

Objective: The contribution of components in cognitive behavior therapy (CBT) to the total reduction of depression symptoms has not been well elucidated, and previous studies couldn't exclude the human factors in the therapy. Design: This is a secondary analysis of a randomized, controlled trial comparing automated smartphone CBT without human factors plus antidepressant switch against antidepressant switch alone among patients with antidepressant-resistant depression. The present CBT consisted of self-monitoring, behavioral activation, and cognitive restructuring. We used linear regression to predict the overall pre- to post-symptom improvement based on improvement achieved by sessions teaching each cognitive or behavioral skill. The overall improvement was measured with the Beck Depression Inventory-II and the session-to-session improvement with K6. Results: Of the 164 participants originally enrolled in the study, 94 participants who completed all K6 evaluation were included in the primary analyses. The results indicated that K6 score reduction in the first half of behavioral activation significantly predicted BDI-II score reduction. The sensitivity analysis including 162 participants did not change the result. K6 score reductions after other CBT sessions did not significantly predict BDI-II score reduction. Conclusion: The behavioral activation seems to contribute to the total reduction of depressive symptoms even if human factors are excluded by using automated smartphone CBT.