Risk of bipolar disorder in patients with endometriosis: A nationwide population-based cohort study

Abstract

Background: Women with endometriosis (EM) have increased vulnerability to certain psychiatric disorders, including depression and anxiety, as well as bipolar disorder (BD). This study investigates the risk of BD development in EM patients. Also, the impact of EM treatment on the risk of developing BD is examined.

Methods: A total of 17,832 EM patients and 17,832 non-EM controls matched by age, index year, and Charlson Comorbidity Index (CCI) score were included between 2000-2012 and followed to the end of 2013. Participants newly diagnosed as BD by board-certified psychiatrist were defined as incidents. Cox regression analysis was used to calculate the hazard ratio (HR) with 95% confidence interval (CI) of the BD incidence rate between two studied groups.

Results: EM patients were associated with an increased risk of BD development compared with non-EM controls after adjusting for age, CCI score, and different treatment options (1.04 versus 0.56 per 1,000 person-years, HR: 2.34, 95% CI: 1.75-3.12). Also, there was no significant difference in the risk estimate between different hormonal or surgical treatment groups, suggesting a limited impact of EM treatment on the risk of BD development.

Limitations: This study deals with the duration of hormonal treatment, whether operated or not, which reduces the chances of showing the effect of individual EM treatment on the risk of BD development.

Conclusion: This study shows that EM patients are associated with an increased risk of BD development. Further studies would be needed to elucidate the mechanism linking the EM and BD.

Keywords: Bipolar disorder; Cohort; Endometriosis; Hormonal treatment; Surgical treatment.