The Prevalence of Depression in Small Intestinal Bacterial Overgrowth

Abstract

Introduction: Many patients who seek care for gastrointestinal symptoms have an associated affective disorder. Gastrointestinal diseases including food allergies, H. Pylori infection, irritable bowel syndrome (IBS), and small intestinal bacterial overgrowth, have all been shown to have an increased probability of depression. The gastrointestinal disease most widely studied in its association with psychiatric disease is irritable bowel syndrome (IBS). There is significant overlap between irritable bowel syndrome and small intestinal bacterial overgrowth (SIBO). The prevalence of SIBO in patients meeting Rome II criteria for IBS was 4-64%. Moreover, ninety-two percent of patients with IBS complain of bloating and abdominal pain, which are also symptoms of SIBO. Thus, we hypothesize that patients with small intestinal bacterial overgrowth will have an increased prevalence of depression as compared to the general population. Methods: 67 subjects were referred for hydrogen breath test to evaluate for small intestinal bacterial overgrowth at Montefiore Medical Center. Data was collected from July 2016 to May 2017. 15 patients were excluded from the study because of: previous treatment of small intestinal bacterial overgrowth, prior rifaximin use, prior gastrointestinal surgery, prior gastrointestinal cancer, or pregnancy. The remaining 52 were provided with validated depression (Patient Health Questionnaire 9) and anxiety (Generalized Anxiety Disorder 7) surveys. Results: Subjects were on average 54 years old, 83% of minority race, 63% female, 37% obese, and 42% had a prior history of depression. Mean Patient Health Questionnaire-9 (PHQ-9) score was 7, with 46% meeting criteria for depression. Thirty patients (58%) tested positive and twenty-two patients (42%) tested negative for small intestinal bacterial growth by hydrogen breath test. Of the patients who tested positive for SIBO, 15 (50%) tested positive for depression and 11 (37%) tested positive for anxiety. Of the patients who tested negative for SIBO, 9 (41%) tested positive for depression and 7 (32%) tested positive for anxiety. There was no significant difference in rate of depression between the SIBO positive and negative cohorts. Conclusion: Although patients with small intestinal bacterial overgrowth had more depression and anxiety in this study, this was not found to be of statistical significance.