RESUMO
BACKGROUND: Metacognitive training (MCT) has been shown to be effective in reducing psychotic symptoms, including delusions. However, less is known on whether MCT, or its specific modules, are effective in ameliorating reasoning biases e.g. belief flexibility. As inflexibility in appraisal has been associated with psychosis and major depressive disorder (MDD), this study examined the efficacy of a 4-session MCT on delusions, depression, and belief flexibility, in two clinical groups (Psychosis and Depression). METHODS: This study adopted a single-blind randomised controlled design, with patients with schizophrenia spectrum disorders (and delusions) and patients with MDD being randomised, respectively, into the MCT condition or a treatment-as-usual (TAU) condition. The MCT intervention consisted of specific modules targeting belief flexibility. Participants were assessed before and after treatment, and at 1- and 6-month follow-ups. RESULTS: Among the 113 participants, 27 patients with psychosis and 29 patients with MDD attended MCT. There were significant improvements in psychotic symptoms, especially delusions, for the Psychosis group, and in depressive symptoms for the MDD group. Symptom improvements following MCT were of large effect sizes, were significantly greater than TAU, and persisted at 6-month. Belief flexibility also improved in both groups, although changes were smaller in size and were not significantly greater than TAU. LIMITATIONS: An active control condition was not included. CONCLUSIONS: This study demonstrated large and stable symptom reductions in delusions and depression, and smaller (yet stable) improvement in belief flexibility across groups, following a 4-session MCT, carrying implications for transdiagnostic process-based interventions and their mechanisms of change.
