Differential Effects of Treatments for Chronic Depression: A Latent Growth Model Reanalysis

Objective: Psychotherapy-pharmacotherapy combinations are frequently recommended for the treatment of chronic depressive disorders. Our aim in this novel reanalysis of archival data was to identify patient subgroups on the basis of symptom trajectories and examine the clinical significance of the resultant classification on basis of differential treatment effects to psychotherapy (cognitive behavioral analysis system of psychotherapy), pharmacotherapy (nefazodone), and their combination. Method: We selected data for 504 patients diagnosed with chronic depression from archival data of a clinical trial (N = 681) and analyzed treatment courses (as assessed by the Hamilton Rating Scale for Depression) using growth mixture models, a contemporary exploratory analysis technique. Results: Three patient subgroups were identified from the typical patterns of change of depression severity during 12-week acute-phase treatment. Within these patient subgroups, differential treatment effects were evident: combination treatment clearly outperformed the 2 monotherapies in the largest patient subgroup, characterized by moderate depression severity, but not in the remaining 2 subgroups, characterized by low and severe depression at baseline. Patient characteristics prior to initiation of treatment enabled allocation of 61% of patients to these subgroups. Conclusions: Research on patient subgroups with different change patterns may support classifications of patients that indicate which treatment is most effective for which type of patient.