LAUSR

Abstract Background: Cognitive behaviour therapy (CBT) has been shown to be effective, yet there is a paucity of research on the differential effectiveness of individual and group CBT for adults with treatment-resistant depression with psychiatric comorbidity. Aims: To investigate the effectiveness of individual and group CBT for inpatients, in an interdisciplinary rehabilitation setting; the extent of psychiatric comorbidity; and who benefits the most from group CBT. Methods: All patients (n = 181) received 6 weeks of rehabilitation (treatment as usual, TAU). In addition, they were randomly allocated to group CBT (n = 86) or individual CBT (n = 59) combined with TAU, or TAU only (n = 36). All CBT therapists were part of an interdisciplinary team, had at least 1-year CBT training, and attended weekly supervision. The same CBT manual was used for individual and group therapy, providing 12 sessions, two per week. Groups had 12–15 participants and two therapists in each session. Results: Individual CBT was superior in efficacy to group CBT and TAU, with a large within-subject effect size (ES = 2.10). Group CBT was not superior to TAU. The benefits of treatment decreased over time, but remained large at 18-month follow-up for individual CBT (ES = 1.02), and medium for group CBT (ES = 0.46) and TAU (ES = 0.60). Conclusions: Individual CBT was an effective addition to TAU and showed significant improvements in symptom severity post-treatment and at 18-month follow-up. Disorder severity and comorbidity may have decreased effectiveness of group therapy primarily aimed at depression.