RESULTS: Compared with the controls, women with endometriosis were 3.5 times more likely to have received a diagnosis of IBS (OR 3.5 [95% CI: 3.1-3.9]). Even after women had been diagnosed with endometriosis, they were still two and a half times more likely to receive a new diagnosis of IBS when compared with the controls (OR 2.5 [95% CI: 2.2-2.8]).