POMC and irritable bowel syndrome: After eliminating non-significant interaction effects, the final model for ACTH included a significant main effect of time (F(4, 236) = 176.46, p < 0.0001), and a significant group (IBS versus control)-by-time interaction effect (F(4, 236) = 4.31, p = 0.0026) (Fig. 2A).