Causal Link of Distinct Mental Disorders with Androgenetic Alopecia and Alopecia Areata: A Bidirectional Two-Sample Mendelian Randomization Study.

Background: The concern that mental states affect the hair-loss has been growing, but the causal evidence is still limited. We aimed to investigate whether and in which direction there is a causal link of distinct mental disorders with androgenetic alopecia (AGA) and alopecia areata (AA) in European population.

Methods: We performed a bidirectional two-sample Mendelian randomization (MR) study to test their causality using summary statistics. The datasets of major depression disorder, anxiety disorder, panic attack, distress, and bipolar disorder were all accessed through the IEU OpenGWAS project. The datasets employed for AGA and AA analysis were sourced from the FinnGen release 10 databases, including 219,469 (220 AGA cases and 219,249 controls) and 394,872 (767 AA cases and 394,105 controls) participants, respectively. We utilized five extensively employed MR techniques to explore the bidirectional causal associations, including inverse variance weighted (IVW), weighted median, MR-Egger, weighted mode, and penalised weighted median.

Results: Based on the IVW method, a bidirectional causal association was revealed whereby major depression disorder is associated with an increased risk of AA (OR: 1.59; 95% CI: 1.16-2.17) and vice versa (OR: 1.02; 95% CI: 1.00-1.03). Notably, the statistical power of MR estimates was both <80%. No association of any genetically predicted mental disorders with AGA was found. Sensitivity analyses substantiated the robustness and reliability of our findings.

Conclusion: Our findings showed a bidirectional causal association between major depression disorder and AA, supporting the importance of therapies aimed at handling mental states for the prevention or treatment of AA rather than AGA.