Clozapine and its protective effect on all-cause, natural, and suicide mortality in patients with schizophrenia: A nationwide cohort study in Taiwan

Aim: Clozapine is indicated as the last-line agent for the treatment of refractory schizophrenia due to its side effects. This study included an Asian schizophrenia population and investigated the effect of clozapine on the risks of all-cause, natural, and suicide mortality. Methods: This study included a large-scale schizophrenia inpatient cohort derived from the National Health Insurance Research Database from January 1, 2001, to December 31, 2019 (n = 43,025). Of them, we selected those who received clozapine (clozapine cohort, n = 5800). From those who never used clozapine, we selected two individuals for each patient in the clozapine cohort by matching by age, sex, and the year of the index date (ratio: 1:2, control cohort, n =11,583). The clozapine and nonclozapine control cohorts together were defined as the study cohort (n = 17,383). Multivariate Cox proportional-hazards regression with a time-dependent model was performed to investigate the effect of individual antipsychotic agents on mortality. Results: All individual first-generation antipsychotics were not associated with mortality risk. However, most individual second-generation antipsychotics exerted protective effects against all-cause and natural mortality. Furthermore, only clozapine and risperidone were significantly associated with a low risk of suicide mortality. Only clozapine exhibited a dose-dependent relationship with all-cause, natural, and suicide mortality. Conclusions: This study provides robust evidence supporting the strong protective effect of clozapine on all-cause, suicide, and natural mortality risks in an Asian population. Under close monitoring, clozapine use can be advantageous in patients with schizophrenia who are at a high risk of suicide.