Cognitive Behavioral Therapy and Interpersonal Psychotherapy as Treatment for Major Depressive Disorder

In this study, the differential effectiveness of CBT and IPT for patients with Major Depressive Disorder, who rate their depression as mild or moderate, will be studied. Both methods are evidence based and recommended by the National Board of Health in Sweden. They are manual based and the patients will receive 14 sessions in each therapy. Their comparative effectiveness has not been studied in Sweden, and their effectiveness with regard to work capacity has not been tested. The hypotheses in the study are that they have equal effect for depression remission, but that CBT is superior when return to work is measured. Three moderator analyses, testing effects for different subgroups, will be made. They propose that patients with attachment avoidance and lower mentalization ability and male patients will have better outcome with CBT. The study will be performed at Sundsvall Hospital, in cooperation with Linköping University. Sundsvall hospital is the only hospital in Sweden where there is a group IPT therapists large enough to make a controlled study possible. The study has a randomized design, with 16 therapists, 8 of them delivering CBT and 8 IPT. The number of patients is 96. The statistical power is .87, with a hypothesized between-groups effect size of d = .40 for return to work, and the significance level of .05 for the between-groups difference. Outcome will be measured as remission of psychiatric diagnosis, decrease in depression severity and frequency of patients who return to work. Both intent-to-treat and completers analyses will be made. The project will go over two years. The study has an effectiveness character in the sense that treatments, although manual based, will be performed in the manner that the therapists usually work, and by having broad inclusion criteria. Treatment integrity will be ascertained by therapist reports and by filming sessions.