Symptom specificity in the acute treatment of Major Depressive Disorder: A re-analysis of the treatment of depression collaborative research program

Abstract

Antidepressant medications, Cognitive-Behavioral Therapy (CBT) and Interpersonal Psychotherapy (IPT) are equally efficacious in the acute treatment of Major Depressive Disorder (MDD). Nevertheless, remission rates remain unacceptably low. Examining the differential time course of remission of specific symptom clusters across treatments may provide a basis for assigning patients to treatments that have the highest chance of being effective. This study re-analyzed data from the NIMH Treatment of Depression Collaborative Research Project (TDCRP), which included 250 adult outpatients with MDD randomized to 16 weeks of CBT, IPT, imipramine+clinical management (IMI-CM), or pill placebo (PLA-CM). We derived four symptom factors from the 23-item Hamilton Depression Rating Scale, and three symptom factors from the Beck Depression Inventory. Within-subject hierarchical regression models were specified to examine the linear and quadratic patterns of symptom remission over five assessment points. IMI-CM produced a more rapid rate of remission than CBT or IPT for both the somatic/vegetative and cognitive-affective symptoms of MDD. There were no statistically significant differences in the rates of improvement of any of the symptom factors between the IMI-CM and PLA-CM groups. Some core symptoms of depression were excluded due to low factor loadings. Past research has argued that the CBT arm in the TDCRP may have been weak. We failed to find evidence that treatments act preferentially on specific symptom clusters. Therefore, the symptoms of MDD may be inter-dependent when it comes to their courses of remission in treatment.