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Background: Observational studies indicate an association between type 1 diabetes (T1D) and suicidal or self-harm behaviors. However, the causal relationship between the 2 remains uncertain. A 2-sample bidirectional Mendelian randomization (MR) analysis to investigate the association between T1D and suicide or self-harm behavior.
Methods: All data were publicly available genome-wide association study summary statistics, and all individuals were of European descent. The inverse variance weighted (IVW) method, MR-Egger regression, and weighted median were employed to investigate the association between T1D and suicide or self-harm behavior. Sensitivity analyses were conducted using Cochran’s Q test, MR-Egger regression, the MR pleiotropy residual sum method, leave-one-out analysis, and the MR residual sum and outlier test to assess the robustness of the findings.
Results: The IVW method indicated an association between T1D and suicidal or self-harm behavior (odds ratio (OR) = 1.011, 95% CI = 1.004-1.018, P = .002). However, there was no observed genetic influence on the relationship between suicidal or self-harm behavior and T1D.
Conclusion: This study, based on bidirectional 2-sample MR analysis of genetic data, validated that T1D is a risk factor for suicidal or self-harm behaviors. These findings are based on data from Europeandescent individuals, and their generalizability to other populations is unknown.
Cite this article as: Ma X, Li R, Chen X, et al. Type 1 diabetes as a causal risk factor for suicide or self-harm: A bidirectional Mendelian randomization study. Psychiatry Clin Psychopharmacol. Published online October 20, 2025. doi:10.5152/pcp.2025.251161.