Patients with polycystic ovary syndrome (PCOS) have an increased risk of developing bipolar disorder, according to study results published in the Journal of Affective Disorders. However, treatment with metformin may slightly reduce the risk for bipolar disorder.

The researchers looked at data collected by the National Health Insurance Program of Taiwan between 2000 and 2012. The final study cohort comprised 7175 patients with PCOS and 28,697 individuals without PCOS, matched by age, index year, and Charlson Comorbidity Index (CCI) score. In addition, patients were categorized into 3 subgroups based on treatment: metformin use, hormone therapy (clomiphene or cyproterone), and no metformin or hormone use. Investigators followed patients until they received a new clinical diagnosis of bipolar disorder, the date of withdrawal from the insurance program, or the end of 2013.  

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Patients with PCOS had an increased risk of developing bipolar disorder compared with patients in the control group, adjusting for age, CCI score, and different treatment (1.05 vs 0.12 per 1000 person-years; hazard ratio [HR], 8.29; 95% CI, 4.65-14.7). In patients with PSCOS, the use of metformin significantly reduced the risk of developing bipolar (HR, 0.36; 95% CI, 0.16-0.81). Treatment with hormone therapy in patients with PCOS showed a lower incidence of bipolar disorder, but the risk estimate was not statistically significant (HR, 0.68; 95% CI, 0.35-1.32).

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Notably, the investigators did not assess the severity of PCOS to evaluate its potential relationship to the risk for bipolar disorder.

The study authors theorized that the interplay between inflammation and cytokines may influence mood and behavioral disturbances, which could explain the overlap between PCOS and bipolar disorder. They also noted, “From a psychological point of view, the chronic burden of PCOS symptoms…can affect the psychological well-being of an individual, which can exacerbate mood swings in patients with [bipolar disorder] subclinical vulnerability and trigger the onset of the disease.”

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Chen S-F, Yang Y-C, Hsu C-Y, Shen Y-C. Risk of bipolar disorder in patients with polycystic ovary syndrome: a nationwide population-based cohort study. J Affect Disord. 2020;263:458-462. doi:10.1016/j.jad.2019.12.007

This article originally appeared on Psychiatry Advisor