Genetic Insights into the Relationship Between Psychiatric Disorders and Irritable Bowel Syndrome: A Mendelian Randomization Analysis

Background Irritable Bowel Syndrome (IBS) is often accompanied by psychiatric conditions, yet the causal relationship remains uncertain. This study leverages Mendelian Randomization to explore the genetic basis of the association between IBS and various psychiatric disorders. Methods We analyzed GWAS data to assess the causal effects of Major Depressive Disorder (MDD), Anxiety, and other psychiatric disorders on Irritable Bowel Syndrome (IBS). Stringent criteria were used to select genetic instrumental variables, and we applied multiple Mendelian Randomization (MR) methods, including a reverse MR analysis, to investigate the impacts comprehensively. Results Our study found a significant causal relationship between IBS and MDD (IVW OR: 1.328, 95% CI: 1.122, 1.572, P=0.001) and a slight but significant link with Anxiety Disorders (IVW OR: 1.0611, 95% CI: 1.0184, 1.1056, P=0.0046). Bipolar Disorder, Schizophrenia, OCD, ADHD, Anorexia Nervosa, and Insomnia did not show significant causal connections with IBS. The reverse MR analysis demonstrated a positive correlation between IBS and MDD (IVW OR: 1.522) and a negative one with ADHD (IVW OR: 0.866), while findings for Schizophrenia and other disorders were not significant. Conclusion The study confirms a unidirectional causal relationship between IBS and certain psychiatric disorders, highlighting the relevance of the gut-brain axis. These insights contribute to the understanding of IBS pathophysiology and underscore the need for considering mental health in IBS management.