Risk of schizophrenia in patients with polycystic ovary syndrome: a nationwide population-based cohort study from Taiwan

To investigate whether patients with polycystic ovary syndrome (PCOS) are at increased risk for incident schizophrenia and whether PCOS treatment (clomiphene, cyproterone, or metformin) affects the incidence of schizophrenia.An overall of 7146 PCOS patients and 28,580 non-PCOS controls matched by age, index year, and Charlson Comorbidity Index (CCI) score were included between 2000 and 2012 and followed up until 2013 using a validated nationally representative sample from Taiwan. Participants newly diagnosed as schizophrenia were defined as incidents. Cox regression analysis was used to calculate the hazard ratio (HR) with a 95% confidence interval (CI) of the schizophrenia incidence rate between the two studied groups.PCOS patients were at increased risk of incident schizophrenia compared to non-PCOS controls after adjusting for age, CCI score, comorbidities, and different treatment options (0.49 versus 0.09 per 1000 person-years, HR: 6.93, 95% CI: 3.25-14.7). After adjusting for above-mentioned covariates, metformin treatment had a protective effect against the incident schizophrenia compared to non-users (HR: 0.16, 95% CI: 0.06-0.41). Also, treatment with clomiphene and cyproterone had only a limited impact on the incident schizophrenia.This study shows PCOS patients are at increased risk of incident schizophrenia, and the metformin treatment has a protective effect against incident schizophrenia.