Sayuk GS, et al. - Opioid use was compared among United States (US) veterans with structural gastrointestinal diagnoses (SGID) and those with unexplained gastrointestinal (GI) symptoms or functional GI diagnoses (FGID), a group for whom opioids have no accepted role. Opioids were prescribed more often for veterans with chronic, unexplained GI symptoms than those with structural diagnoses, despite the potential for adverse consequences. Psychiatric comorbidities and frequent health-care encounters mediated some of the opioid use risk.