Impacts of opioid use, postoperative pain, pain interference, and side effects on postoperative psychological distress: a retrospective study of the PAIN OUT registry in seven Asian regions

Postoperative psychological distress is highly prevalent in Asian surgical populations, but the relationships among opioid exposure at different perioperative stages, pain characteristics, side effects, and postoperative anxiety and helplessness remain poorly understood. A total of 6,105 patients from seven Asian regions in the PAIN OUT registry were included. Opioid use during the preoperative, intraoperative, recovery room, and ward stages was converted to oral morphine equivalents (OMEs). Four dimensions of postoperative outcomes– psychological distress (anxiety, helplessness), pain intensity, pain interference, and side effects– were assessed using the International Pain Outcomes Questionnaire (IPO-Q). Multinomial logistic regressions were used to examine the associations. Moderate-to-severe anxiety and helplessness were reported by 42.6% and 27.9% of patients, respectively. Time spent in severe pain showed the strongest associations with anxiety (moderate phase: OR = 2.711 [2.238, 3.285] for moderate anxiety; OR = 2.295 [1.72, 3.071] for severe anxiety), while maximum pain severity was less predictive. Sleep interference was most strongly associated with helplessness (severe interference: OR = 3.307 [2.317, 4.720] for severe helplessness; OR = 2.738 [1.94, 3.86] for severe anxiety). Common side effects– dizziness (ORs: 1.535–2.643), drowsiness (ORs: 1.426–1.881), and itching (ORs: 1.428–1.917)—were significantly associated with both anxiety and helplessness. For opioid exposure, higher intraoperative and ward OMEs were modestly associated with lower distress (ORs: 0.969–0.982 per 10-mg increment), while preoperative and recovery-room OMEs showed no significant associations. Counterintuitively, moderate-to-severe maximum pain was associated with lower odds of moderate helplessness (ORs: 0.679–0.687). In this Asian cohort, pain duration and sleep disruption were more strongly associated with postoperative psychological distress than pain severity. The timing of opioid administration (intraoperative and ward) showed modest associations, suggesting that when opioids are used may be as important as the total dose. Integrated postoperative care should prioritize rapid resolution of prolonged pain episodes, proactive nighttime symptom management, and structured monitoring of common opioid-related side effects to reduce early postoperative distress.