Causal effects of schizophrenia on sleep and eating disorders: A Mendelian randomization study

Previous studies have suggested a potential connection between schizophrenia (SCZ) and sleep and eating disorders. However, these studies have not sufficiently accounted for potential confounding factors, leaving the true causal relationship unclear. Understanding this causal link is essential for developing effective prevention and treatment strategies. To address this gap, we aim to investigate the causal effect of SCZ on sleep and eating disorders using Mendelian randomization (MR) analysis. This method offers a more robust approach by leveraging genetic variants as instrumental variables to rigorously examine the relationship between SCZ and its comorbidities. We conducted bidirectional MR analyses using genome-wide association study summary statistics of SCZ, sleep disorders, and eating disorders. These analyses were conducted after confirming adherence to the 3 core MR assumptions, removing instrumental variables with confounding effects, and directionally harmonizing all data. Then we used Cochran Q test, MR-Egger intercept analysis, and leave-one-out method to conduct the sensitivity analysis of this study to test its heterogeneity and pleiotropy. The results of the inverse-variance weighted (IVW) approach suggest that SCZ increases the risk of sleep disorders (IVW: odds ratio [OR] = 1.041, 95% confidence interval [CI]: 1.012-1.070, P < .01), whereas studies in the opposite direction have not found an effect of sleep disorders on SCZ. The results of IVW suggest that SCZ increases the risk of eating disorders (IVW: OR = 1.228, 95% CI: 1.090-1.384, P < .001), and the weighted median (WM) method similarly provided evidence that SCZ increases the risk of eating disorders (WM: OR = 1.200, 95% CI: 1.019-1.407, P < .05). This study concluded that SCZ is causally associated with sleep and eating disorders. In clinical practice, psychiatrists should pay attention to the daily sleep and eating status of patients with SCZ, and take appropriate measures and countermeasures as early as possible if there is any abnormality.