Concomitant use of H2 blocker(s) did not significantly affect the incidence of OCD-like symptoms induced by D2R agonists (Supplementary Fig. 1C, a hazard ratio of 1.10, 95% CI: 0.359–3.39, P = 0.090 in the log-rank test; Supplementary Tables 12–17), suggesting that the inhibitory effects of PPIs on the incidence of OCD-like symptoms did not result from the inhibition of gastric acid secretion and history of gastrointestinal diseases. Here, DRD2 is linked to gastrointestinal disease.