BackgroundThe relationship between sleep disorders and psychiatric disorders has been extensively studied in epidemiological research. However, whether specific sleep-related traits are associated with psychiatric disorders through potential causal mechanisms remains incompletely understood.MethodsThis study employed a two-sample Mendelian randomization (MR) analysis method to investigate potential causal associations between six sleep-related traits and eleven psychiatric disorders. MR analyses were performed using inverse variance weighting (IVW), weighted median, and MR-Egger methods. Cochran’s Q test was used to assess heterogeneity, while MR-Egger intercept analysis and MR-PRESSO (Mendelian Randomization Pleiotropy RESidual Sum and Outlie) were applied to evaluate potential horizontal pleiotropy. In addition, a retrospective observational study was conducted using clinical data from the First Affiliated Hospital of Soochow University between November 2023 and December 2025. Logistic regression analysis was performed to assess the association between sleep disorders and psychiatric disorders.ResultsMR analyses identified potential associations between sleep-related traits and psychiatric disorders. Genetically predicted insomnia was associated with an increased risk of major depressive disorder (OR = 2.22, 95% CI: 1.66–2.97, P < 0.001). In the retrospective clinical cohort, individuals with sleep disorders exhibited a higher prevalence of psychiatric disorders (adjusted OR = 1.71, 95% CI: 1.09–2.69, P = 0.020). The consistency between genetic evidence and clinical observational findings provides complementary support for the clinical relevance of the observed association.ConclusionBy integrating MR analyses with retrospective clinical observational data, this study provides genetic and clinical evidence supporting an association between sleep disorders and psychiatric disorders. These findings suggest that sleep disturbances may represent potential modifiable factors associated with mental health outcomes and highlight the importance of sleep-related interventions in psychiatric disease prevention and management.