Abstract
Post-traumatic stress disorder (PTSD) and Attention deficit and hyperactivity disorder (ADHD) are common mental illnesses. Observational studies have indicated that these conditions often co-occur with gastrointestinal diseases. However, the causal relationship between PTSD and ADHD with gastrointestinal diseases remain unclear. We conducted Mendelian randomization (MR) analysis to investigate these associations. We selected genetic instrument data with genome-wide significance levels for PTSD and ADHD from the psychiatric genomics consortium open genome-wide association study platform. Summary statistics for the 24 gastrointestinal diseases were obtained from the FinnGen study. We used the "TwoSampleMR" package in R to perform a 2-sample MR analysis and conducted sensitivity analysis of the results. We found that genetic susceptibility to PTSD was associated with 1 gastrointestinal disease, specifically pancreatic cancer (P = .003; odds ratios [OR] = 1.295; 95% CI, 1.094-1.531). Genetic susceptibility to ADHD was associated with 4 gastrointestinal diseases: gastroesophageal reflux (P = .014; OR = 1.100; 95% CI, 1.020-1.186), gastric ulcer (P = .004; OR = 1.208; 95% CI, 1.061-1.376), duodenal ulcer (P = .020; OR = 1.206; 95% CI, 1.029-1.413), and chronic gastritis (P = .021; OR = 1.122; 95% CI, 1.018-1.237). This study provides MR evidence supporting causal relationship between PTSD and ADHD with specific gastrointestinal diseases.