Individualized metacognitive therapy for delusions: A randomized controlled rater-blind study

Theory-driven interventions targeting specific factors that contribute to delusions are receiving increased interest. The present study aimed to assess the efficacy of individualized metacognitive therapy (MCT+), a short manualized intervention that addresses delusion-associated cognitive biases.; 92 patients with current or past delusions were randomized to receive 12 twice-weekly sessions of either MCT+ or a control intervention within a randomized controlled rater-blind design. Psychopathology and cognitive biases were assessed at baseline, 6 weeks and 6 months. ANCOVAs adjusted for baseline scores were used to assess differences between groups regarding outcome variables. Both per-protocol and intention-to-treat analyses were conducted.; At 6 weeks, there was a significant difference in favor of MCT+ regarding decrease in delusion severity and improvement of self-reflectiveness (medium effect size), and a trend-wise difference regarding probability thresholds to decision. These effects increased, when only patients attending a minimum of 4 therapy sessions were considered. Control group patients subsequently showed further improvement while patients in the MCT+ group remained stable, such that there were no differences between groups at the 6-month follow-up.; Lower attendance rates in the control group possibly leading to unequal therapeutic effort; lower baseline delusion severity in the MCT+ group.; The result pattern suggests that MCT+ led to earlier improvement in delusions and cognitive biases compared to the control intervention. The absence of a long-term effect might reflect floor effects in the MCT+ group, but may also indicate the need for further measures to promote sustainability of MCT+ effects.