Metacognitive training (MCT) for schizophrenia spectrum is widely implemented. It is timely to systematically review the literature and to conduct a meta-analysis.

Eligible studies were selected from several sources (databases and expert suggestions). Criteria included comparative studies with a MCT condition measuring positive symptoms and/or delusions and/or data-gathering bias. Three meta-analyses were conducted on data gathering (three studies; 219 participants), delusions (seven studies; 500 participants) and positive symptoms (nine studies; 436 participants). Hedges’ g is reported as the effect size of interest. Statistical power was sufficient to detect small to moderate effects.

All analyses yielded small non-significant effect sizes (0.26 for positive symptoms; 0.22 for delusions; 0.31 for data-gathering bias). Corrections for publication bias further reduced the effect sizes to 0.21 for positive symptoms and to 0.03 for delusions. In blinded studies, the corrected effect sizes were 0.22 for positive symptoms and 0.03 for delusions. In studies using proper intention-to-treat statistics the effect sizes were 0.10 for positive symptoms and −0.02 for delusions. The moderate to high heterogeneity in most analyses suggests that processes other than MCT alone have an impact on the results.

The studies so far do not support a positive effect for MCT on positive symptoms, delusions and data gathering. The methodology of most studies was poor and sensitivity analyses to control for methodological flaws reduced the effect sizes considerably. More rigorous research would be helpful in order to create enough statistical power to detect small effect sizes and to reduce heterogeneity. Limitations and strengths are discussed.

Metacognitive training (MCT) for patients with psychosis is a psychological group intervention that aims to educate patients about common cognitive biases underlying delusion formation and maintenance, and to highlight their negative consequences in daily functioning.

In this randomized controlled trial, 154 schizophrenia spectrum patients with delusions were randomly assigned to either MCT + treatment as usual (TAU) or TAU alone. Both groups were assessed at baseline, and again after 8 and 24 weeks. The trial was completed fully by 111 patients. Efficacy was measured with the Psychotic Symptom Rating Scales (PSYRATS) Delusions Rating Scale (DRS), and with specific secondary measures referring to persecutory ideas and ideas of social reference (the Green Paranoid Thoughts Scale, GPTS), cognitive insight (the Beck Cognitive Insight Scale, BCIS), subjective experiences of cognitive biases (the Davos Assessment of Cognitive Biases Scale, DACOBS) and metacognitive beliefs (the 30-item Metacognitions Questionnaire, MCQ-30). Economic analysis focused on the balance between societal costs and health outcomes (quality-adjusted life years, QALYs).

Both conditions showed a decrease of delusions. MCT was not more efficacious in terms of reducing delusions, nor did it change subjective paranoid thinking and ideas of social reference, cognitive insight or subjective experience of cognitive biases and metacognitive beliefs. The results of the economic analysis were not in favour of MCT + TAU.

In the present study, MCT did not affect delusion scores and self-reported cognitive insight, or subjective experience of cognitive biases and metacognitive beliefs. MCT was not cost-effective.