Abstract
OBJECTIVE: Acceptance and commitment therapy (ACT) is a third-wave psychological intervention that has attracted considerable clinical and research attention. A previous meta-analysis of ACT trials in psychosis reported a large effect size of ACT against overall psychotic symptomatology. However, there were critical methodological issues in the review that justify replication. METHODS: Systematic review and meta-analysis of randomized controlled trials (RCTs) testing ACT vs. any comparator condition in a sample of adults with psychosis. The outcome of interest was overall psychotic symptomatology. RESULTS: The search identified seven published and eight unpublished trials (of which we were able to obtain data from one). Data on symptomatology were extracted from six trials that involved 274 participants. The summary effect size (Hedge's G) for overall symptomatology was small and not significant (-0.21, 95%CI -0.60-0.18). Trials were generally rated as having a high risk of bias. Safety reporting was inadequate across included trials. CONCLUSIONS: Our observed effect size contrasted with that reported in a previous meta-analysis; differences were likely explained by errors in data extraction. The findings of this review suggest that there is currently inadequate evidence to conclude that ACT is a safe and effective treatment against psychotic symptomatology. SYSTEMATIC REVIEW REGISTRATION: CRD42018097200.