Childhood appendectomy and adult mental disorders: A population-based cohort study.

Abstract

Recent studies suggest that disruption of the colonic microbiota homeostasis is associated with low-grade systemic inflammation and mental disorders. The cecal appendix may influence the homeostasis of the colonic microbiota. In this large population-based study, we investigated whether early removal of the appendix is associated with an increased risk of mental disorders later in life. All Swedish individuals born between 1973 and 1992 (N = 1,937,488) were included and followed prospectively until December 31, 2016 for any psychiatric International Classification of Disease diagnosis from age 14 or later in life. The main exposure was defined as having a history of appendectomy before age 14 (N = 44,259); the second exposure, appendicitis before age 14 but without appendectomy (N = 1,542), and the third exposure studied was a history of hernia surgery before age 14 (N = 35,523). Control groups for each respective exposure were all unexposed individuals in the study population. Individuals exposed to appendectomy before age 14 had a 19% increased risk of depressive disorder (adjusted hazard ratio [aHR] = 1.19; 95% confidence interval [95% CI]: 1.15-1.23), 27% increased risk of bipolar affective disorder (aHR = 1.27; 95% CI: 1.17-1.37), and a 20% increased risk of an anxiety disorder (aHR = 1.20; 95% CI: 1.16-1.23) compared to individuals unexposed to childhood appendectomy. We found no association between appendectomy and increased risk of obsessive-compulsive disorder and schizophrenia and there was no association between appendicitis without appendectomy and mental disorders. The association between childhood hernia surgery and mental disorders later in life was small but significant. Childhood appendectomy, but not appendicitis without appendectomy, was associated with a significantly increased risk of mood and anxiety disorders in adulthood.