Epidemiological evaluations of methadone adherence in opioid dependent offenders: Implications for public health and public safety

Background: Opioid use is associated with elevated rates of morbidity and mortality and has a significant impact on public health and public order. Justice involved individuals are disproportionately affected by opioid related harms but effective interventions are underutilized. Methadone maintenance treatment is the best researched and mostly widely implemented pharmacotherapy option for the treatment of opioid dependence. Despite its demonstrated efficacy in general populations, few studies have examined its effectiveness among patients with criminal justice histories and complex health and social challenges. This thesis aims to address the deficits in existing extant literature through three unique research studies described herein. Methods: All studies were conducted using a retrospective cohort design involving linked population-level administrative data. Participants comprised a cohort of individuals from British Columbia, Canada with histories of convictions and who filled a methadone prescription. Three independent analyses estimated the effect of methadone on crime, mortality and hospitalization. Methadone was divided into medicated (methadone was dispensed) and nonmedicated (methadone was not dispensed) periods and analyzed as a time-varying exposure. Cox regression was used in all three analyses and hazard ratios with 95% confidence intervals were reported as an effect size. In all instances additional subgroup and sensitivity analyses were performed. Results: Over a mean follow-up time of eight years, findings from the sample (n=14, 530) revealed a significant association between dispensed methadone and lower rates of violent and non-violent crime; all-cause and cause-specific mortality; and any-cause hospitalization (n=11, 401) even after controlling for a number of covariates. Findings for crime and hospitalization analyses demonstrated the magnitude of protective effect for methadone was greatest during the initial years following methadone treatment initiation but decayed in periods exceeding a decade. Subgroup and sensitivity analyses demonstrated a similar pattern of results. Conclusions: Adherence to methadone is associated with lower rates of opioid related harms among justice involved patients with opioid dependence. Results consistently point to the need for increased access to methadone and higher rates of adherence for offenders and similarly marginalized groups. Implementation of evidence-based policies and programs are required to improve adherence and promote recovery in this vulnerable population.