BACKGROUND: Although antipsychotic medication is the first line of treatment for schizophrenia, many service users choose to refuse or discontinue their pharmacological treatment. Cognitive therapy (CT) has been shown to be effective when delivered in combination with antipsychotic medication, but has yet to be formally evaluated in its absence. This study evaluates CT for people with psychotic disorders who have not been taking antipsychotic medication for at least 6 months.MethodTwenty participants with schizophrenia spectrum disorders received CT in an open trial. Our primary outcome was psychiatric symptoms measured using the Positive and Negative Syndromes Scale (PANSS), which was administered at baseline, 9 months (end of treatment) and 15 months (follow-up). Secondary outcomes were dimensions of hallucinations and delusions, self-rated recovery and social functioning. RESULTS: T tests and Wilcoxon's signed ranks tests revealed significant beneficial effects on all primary and secondary outcomes at end of treatment and follow-up, with the exception of self-rated recovery at end of treatment. Cohen's d effect sizes were moderate to large [for PANSS total, d=0.85, 95% confidence interval (CI) 0.32-1.35 at end of treatment; d=1.26, 95% CI 0.66-1.84 at follow-up]. A response rate analysis found that 35% and 50% of participants achieved at least a 50% reduction in PANSS total scores by end of therapy and follow-up respectively. No patients deteriorated significantly. CONCLUSIONS: This study provides preliminary evidence that CT is an acceptable and effective treatment for people with psychosis who choose not to take antipsychotic medication. An adequately powered randomized controlled trial is warranted.