Aim of the current study is to investigate the long-term efficacy of Metacognitive Training for Depression (D-MCT) and to explore whether previously observed effects at the 6-month follow-up of a randomized, controlled, assessor-blind, parallel group trial are maintained at the 3-year follow-up.

Dissemination of treatment for depression is still unsatisfying: every second patient does not receive, refuses, or is waiting for treatment. Moreover, with a drop-out rate of almost 25% in routine clinical practice, and a 54% relapse rate for treatment responders within the two years after treatment termination, improving treatment is necessary. Metacognitive Training for depression (D-MCT), a low threshold, easy to administer group intervention was designed to fill this gap. It aims at the reduction of depressive symptoms by changing cognitive biases; not only biases targeted in cognitive behavioral therapy but also those identified by basic research. It was positively evaluated with regard to feasibility and acceptance in a non-randomized pilot study. Moreover, efficacy of D-MCT was suggested in a randomized controlled trail (RCT) in comparison to an active control intervention (Jelinek et al., in press). In this trial patients with depressive disorder were completing a psychosomatic outpatient treatment program and were randomly assigned to either D-MCT or general health training. Severity of depression and cognitive biases were assessed at baseline (t0), post treatment (t1) and 6 months (t2) later by raters blind to diagnostic status. Intention-to-treat analyses demonstrated that at the end of treatment, as well as 6 months later, improvement in depression was significantly greater in the D-MCT relative to the health training group at medium effect sizes. A significantly greater number of patients in the D-MCT group were in remission at 6-month follow-up. Moreover, the decrease in cognitive biases and increase in psychological well-being/quality of life was larger in the D-MCT than the health training group over time. Aim of the current study is to investigate the long-term efficacy of D-MCT. For this purpose, an additional 3 year follow-up assessment (t3) is conducted. The Hamilton Depression Rating Scale (HDRS, 17-item version) total score serves as the primary outcome. Self-assessed depression, dysfunctional beliefs, self-esteem, quality of life, and ability to work serve as secondary outcomes.

Inclusion Criteria for the current study are:

• informed consent
• intention-to-treat-sample of the study Evaluation of Metacognitive Training for Depression (D-MKT) in psychosomatic rehabilitation, DRKS-ID: DRKS00007907 (see Jelinek et al., in press, Psychotherapy and Psychosomatics)
• age between 18 and 65 years
• diagnosis of a single episode or recurrent major depressive disorder (MDD) or dysthymia (verified by the MINI).

The exclusion criteria were:

• lifetime psychotic symptoms (i.e., hallucinations, delusions, or mania), suicidality (Suicidal Behaviors Questionnaire-Revised ≥ 7), intellectual disability (estimated IQ < 70).