Investigating social deprivation and comorbid mental health diagnosis as predictors of treatment outcomes among patients with an opiate use disorder using substance use services: a prospective cohort study

ABSTRACT: Aims We investigated whether social deprivation and comorbid mental health diagnoses were predictors of subsequent engagement with substance use services or crisis and inpatient services amongst people with an opioid related disorder diagnosed in secondary mental health care. Design Prospective cohort study, using anonymised electronic health records from a substance use and secondary mental health care provider. Setting Camden and Islington, London, UK. Participants We followed 1,888 individuals with either an opioid use disorder diagnosis or prescription for methadone or buprenorphine for one-year after initial substance use service engagement between September 2015 and May 2020. Measurements Our primary outcomes were rates of subsequent engagement with substance use and crisis/inpatient services. Our secondary outcome was time to first contact with a crisis/inpatient service. Exposures were social deprivation quartile and comorbid mental health diagnoses. We assessed associations using Poisson regression and Cox proportional survival analyses. Results Rates of subsequent engagement with substance use services were not associated with social deprivation but were increased for those with a single comorbid mental health diagnosis (incidence rate ratio [IRR]: 1.69; 95%CI: 1.24 to 2.31). Rates of contact with crisis/inpatient services were lower in those in the most versus least deprived quartile (IRR: 0.44; 95%CI: 0.31 to 0.61) but elevated for those with single (IRR: 3.41; 95%CI: 2.58 to 4.49) or multiple comorbid mental health diagnoses (IRR: 5.01; 95%CI 4.02 to 6.24). For our secondary outcome, deprivation did not predict time to first contact, but single (Hazard Ratio [HR]: 4.15; 95%CI 2.71 to 6.35) and multiple (HR: 4.49; 95%CI 3.15 to 6.39) comorbid mental health diagnoses led to earlier contact with crisis/inpatient services. Conclusion Our findings illustrate greater substance and secondary mental health care service use amongst opioid users with diagnosed comorbid mental health conditions.