TNF and endometriosis: Additionally, there was an indication of effect modification by analgesic pain medication use (p-het = 0.07), with a significant inverse association between pain with bowel movements and TNF-α among the endometriosis cases not using analgesics (p = 0.009) but a non-significant positive association among the cases using analgesics at the blood draw (p = 0.33; Table S10).