A Mendelian randomization study of the associations between depression, anxiety and clinical conditions including...

Given the high prevalence of psychological and physical conditions as well as the limited understanding of the potential causal links, we aim to explore the associations between psychological problems (depression and anxiety) and physical health issues (thyroid nodules, flatulence, menstrual disorders).

Genetic data on depression and anxiety were sourced from the Psychiatric Genomics Consortium and the FinnGen database, respectively. Meanwhile, datasets of the Epidemiological Network were employed to investigate thyroid nodules, flatulence, and menstrual irregularities. The Mendelian randomization (MR) analysis was conducted with the TwoSampleMR R package. To ensure the accuracy and detect horizontal pleiotropy, the inverse variance weighting, MR-Egger regression, and weighted averaging were employed. Additionally, the Cochran Q heterogeneity test was applied to assess the heterogeneity. Moreover, the stability of the findings was assessed using the leave-one-out method. Finally, the supplementary MR and multivariate MR analyses were utilized to verify the consistency of the associations.

Our analysis demonstrated that depression significantly influenced the development of thyroid nodules (P = .034, odds ratio = 1.75, confidence interval [1.0419, 2.9392]) and irregular menstruation (P = .02, odds ratio = 1.005, confidence interval [1.0008, 1.0097]) but had no effect on flatulence (P = .156). However, the inverse variance weighting P-values for anxiety in all outcomes showed no causal association with any of the studied conditions.

MR analysis showed that depression causally worsens thyroid nodules and menstrual irregularities, while anxiety has no such association. Moreover, depression continuously impacts menstrual irregularities, even after anxiety adjustment. Our findings highlight the importance of mental health in managing physical health.