We evaluated the effectiveness and acceptability of metacognitive interventions for mental disorders. We searched electronic databases and included randomized and nonrandomized controlled trials comparing metacognitive interventions with other treatments in adults with mental disorders. Primary effectiveness and acceptability outcomes were symptom severity and dropout, respectively. We performed random‐effects meta‐analyses. We identified Metacognitive Training (MCTrain), Metacognitive Therapy (MCTherap), and Metacognition Reflection and Insight Therapy (MERIT). We included 49 trials with 2,609 patients. In patients with schizophrenia, MCTrain was more effective than a psychological treatment (cognitive remediation, SMD = −0.39). It bordered significance when compared with standard or other psychological treatments. In a post hoc analysis, across all studies, the pooled effect was significant (SMD = −0.31). MCTrain was more effective than standard treatment in patients with obsessive–compulsive disorder (SMD = −0.40). MCTherap was more effective than a waitlist in patients with depression (SMD = −2.80), posttraumatic stress disorder (SMD = −2.36), and psychological treatments (cognitive–behavioural) in patients with anxiety (SMD = −0.46). In patients with depression, MCTherap was not superior to psychological treatment (cognitive–behavioural). For MERIT, the database was too small to allow solid conclusions. Acceptability of metacognitive interventions among patients was high on average. Methodological quality was mostly unclear or moderate. Metacognitive interventions are likely to be effective in alleviating symptom severity in mental disorders. Although their add‐on value against existing psychological interventions awaits to be established, potential advantages are their low threshold and economy.

Objectives A recent trial comparing Cognitive Behavioral Analysis System of Psychotherapy (CBASP) and supportive psychotherapy in chronic depression found CBASP to be more effective in treating depressive symptoms. We aimed to evaluate adverse events that occurred during this trial. Materials and Method A randomized trial of chronically depressed outpatients was performed. The treatment included 32 sessions of CBASP or supportive psychotherapy. Therapists asked patients about adverse events and their intensity in each session using a standardized checklist. We analyzed the mean number of (severe) adverse events per patient up to Session 32 with gamma frailty recurrent event models. Results Two hundred and sixty patients were included in the analyses (66% female, mean age 45 years). Patients in the supportive psychotherapy group reported less severe adverse events in general, and less severe adverse events related to personal life and to occupational life than patients in the CBASP group. Less adverse events related to suicidal thoughts were reported in the CBASP compared with the supportive psychotherapy group. Conclusions Differences in the adverse events profile may be explained by the treatment elements. Adverse events related to personal and occupational life for example might be considered a necessary and expected yet temporary adverse treatment outcome of an effective CBASP treatment.