Psychiatric Morbidity Following Intestinal Infectious Diseases: A Nationwide Cohort Study in South Korea.

Intestinal infectious diseases (IIDs), typically considered self-limiting, may exert lasting effects on mental health. This nationwide retrospective cohort study investigated the association between recurrent IID and the subsequent development of psychiatric disorders in South Korea. Using data from the National Health Insurance Service-National Sample Cohort (2002-2013), adults with three or more IID diagnoses were matched to controls without IID by age, sex, and health screening year. Eight psychiatric outcomes were examined: depressive disorder, bipolar disorder, anxiety disorder, obsessive-compulsive disorder (OCD), adjustment disorder, organic mental disorders, schizophrenia, and alcohol use disorder. Patients with recurrent IID showed significantly increased risks for depressive disorder (adjusted hazard ratio [aHR], 2.14), bipolar disorder (aHR, 1.80), anxiety disorder (aHR, 2.20), OCD (aHR, 3.84), adjustment disorder (aHR, 2.33), and organic mental disorders (aHR, 1.67). Psychiatric risks were disproportionately higher among younger individuals and male patients. A dose-dependent increase in psychiatric risk was observed with higher IID frequency. No significant associations were found for schizophrenia or alcohol use disorder in the overall analysis, although subgroup analyses revealed elevated risks with higher IID exposure. These findings suggest that recurrent IID may contribute to psychiatric morbidity via gut-brain axis disruption and systemic inflammation. Clinical attention to mental health following IID episodes, particularly in vulnerable populations, may be warranted.