INTRODUCTION Despite a high prevalence of opioid use disorder (OUD) among people in prison, there is little knowledge of how many receive the recommended opioid agonist treatment (OAT) and what characterizes those who receive OAT and those who do not when it comes to mental health comorbidities. We aimed to describe people with OUD in Norwegian prisons over a ten-year period and their OAT status, and to investigate comorbidity of mental health disorders stratified by gender.

METHODS Data from the PriSUD study, including all people (≥19 years old) imprisoned in Norway between 2010 and 2019, linked to national patient registry data, including ICD-10 codes. We calculated the prevalence (1-year and 10-year) of OUD and OAT, and mental health comorbidity stratified on OAT-status and gender.

RESULTS Among the cohort (n=51,148), 7 282 (14.2%) were diagnosed with OUD during the period of observation. Of those, 4 689 (64.4%) received OAT. People with OUD had high levels of comorbidity, including other drug use disorders (92.4% OAT, 90.3% non-OAT), alcohol use disorder (32.1% OAT, 44.4% non-OAT) and any other mental health disorders (61.6% OAT, 68.2% non-OAT). The proportion receiving OAT among people with OUD increased markedly during the ten years of observation; from 35.7% in 2010-70.9% in 2019.

CONCLUSION People with OUD, both receiving OAT and not, had substantially more mental health comorbidities than the non-OUD population. Understanding how the prison population changes over time especially in terms of mental health needs related to OUD, is important for correctional health service planning.