The relationship between opioid use and the incidence of psychiatric disorders remains unidentified.

This study examined the association between the incidence of psychiatric disorders and opioid use.

Data for this population-based cohort study were obtained from the National Health Insurance Service of South Korea. The study included all adult patients who received opioids in 2016. The control group comprised individuals who did not receive opioids in 2016, and were selected using a 1:1 stratified random sampling procedure. Patients with a history of psychiatric disorders diagnosed in 2016 were excluded. The primary end-point was the diagnosis of psychiatric disorders, evaluated from 1 January 2017 to 31 December 2021. Psychiatric disorders included schizophrenia, mood disorders, anxiety and others.

The analysis included 3 505 982 participants. Opioids were prescribed to 1 455 829 (41.5%) of these participants in 2016. Specifically, 1 187 453 (33.9%) individuals received opioids for 1–89 days, whereas 268 376 (7.7%) received opioids for ≥90 days. In the multivariable Cox regression model, those who received opioids had a 13% higher incidence of psychiatric disorder than those who did not (hazard ratio 1.13; 95% CI 1.13–1.14). Furthermore, both those prescribed opioids for 1–89 days and for ≥90 days had 13% (hazard ratio 1.13, 95% CI 1.12–1.14) and 17% (hazard ratio 1.17, 95% CI 1.16–1.18) higher incidences of psychiatric disorders, respectively, compared with those who did not receive opioids.

This study revealed that increased psychiatric disorders were associated with opioid medication use. The association was significant among both short- and long-term opioid use.