Clozapine as a treatment for catatonia: A systematic review.

Catatonia is a neuropsychiatric disorder characterised by altered movement, speech, and behaviour. Clozapine is an established therapy for treatment-resistant schizophrenia, but its role in catatonia has not been systematically examined. In this systematic review, we aimed to assess the evidence for clozapine as a treatment for catatonia. Full text original research articles in English where at least one patient with catatonia was treated with clozapine were included, provided catatonia did not occur solely in the context of neuroleptic malignant syndrome. Results were tabulated with calculations of summary statistics presented. Risk of bias was assessed with the Tool for Evaluating the Methodological Quality of Case Reports and Case Series. 182 patients were included, 81 from cohort studies and 101 from case reports or case series. 119/182 patients (65 %) had a specified underlying diagnosis of schizophrenia. Over 80 % of reported patients with catatonia had at least partial remission following treatment with clozapine across both cohort studies and case reports and case series. Among the case reports and series, 24/101 patients (23.8 %) followed clozapine withdrawal. Overall, 25 studies were of low quality, 60 of moderate quality and 8 of high quality. Our findings should be interpreted with caution, as the reliance on case reports, case series and small cohort studies is susceptible to reporting biases, regression to the mean and confounding by other treatments. Future research could use large healthcare databases to ascertain outcomes in those on clozapine with a history of catatonia given the difficulty and expense of conducting randomised controlled trials.