Prevalence of co‐occurring mental illness and substance use disorder and association with overdose: a linked data cohort study among residents of British Columbia, Canada

Abstract

Aims To estimate the treated prevalence of mental illness, substance use disorder (SUD) and dual diagnosis and the association between dual diagnosis and fatal and non‐fatal overdose among residents of British Columbia (BC), Canada. Design A retrospective cohort study using linked health, income assistance, corrections and death records. Setting British Columbia (BC), Canada. Participants A total of 921 346 BC residents (455 549 males and 465 797 females) aged 10 years and older. Measurements Hospital and primary‐care administrative data were used to identify a history of mental illness only, SUD only, dual diagnosis or no history of SUD or mental illness (2010–14) and overdoses resulting in medical care (2015–17). We calculated crude incidence rates of non‐fatal and fatal overdose by dual diagnosis history. Andersen–Gill and competing risks regression were used to examine the association between dual diagnosis and non‐fatal and fatal overdose, respectively, adjusting for age, sex, comorbidities, incarceration history, social assistance, history of prescription opioid and benzodiazepine dispensing and region of residence. Findings Of the 921 346 people in the cohort, 176 780 (19.2%), 6147 (0.7%) and 15 269 (1.7%) had a history of mental illness only, SUD only and dual diagnosis, respectively; 4696 (0.5%) people experienced 688 fatal and 6938 non‐fatal overdoses. In multivariable analyses, mental illness only, SUD only and dual diagnosis were associated with increased rate of non‐fatal [hazard ratio (HR) = 1.8, 95% confidence interval (CI) = 1.6–2.1; HR = 9.0, 95% CI = 7.0–11.5, HR = 8.7, 95% CI = 6.9–10.9, respectively] and fatal overdose (HR = 1.6, 95% CI = 1.3–2.0, HR = 4.3, 95% CI = 2.8–6.5, HR = 4.1, 95% CI = 2.8–6.0, respectively) compared with no history. Conclusions In a large sample of residents of British Columbia (Canada), approximately one in five people had sought care for a substance use disorder or mental illness in the past 5 years. The rate of overdose was elevated in people with a mental illness alone, higher again in people with a substance use disorder alone and highest in people with a dual diagnosis. The adjusted hazard rates were similar for people with substance use disorder only and people with a dual diagnosis.

Concurrent use of opioids and stimulants and risk of fatal overdose: A cohort study

“…Prior studies have demonstrated that factors such as sex, age, comorbidities, substance use history, and concurrent prescriptions can contribute to risk of overdose and overdose mortality [24][25][26]. As such, a series of confounding Cox proportional hazard models were performed to evaluate the relationship between type of substance use and illicit drug toxicity death.…”

Suicidality as a Predictor of Overdose among Patients with Substance Use Disorders

“…Similarly, mental health conditions are highly prevalent in persons with stimulant use disorders, with 35.7 to 41.6% having a lifetime history of major depression [ 8 ] and between 23 to 42% with lifetime history of PTSD [ 12 ]. Depressive symptoms along with other mental health conditions have been associated with nonfatal overdoses among individuals with SUD, drawing attention to the importance of early identification and treatment for these co-occurring conditions [ 6 , 13 , 14 ].…”

Comorbid Affective and Substance Use Disorders of Medicaid/Medicare Beneficiaries at an Opioid Treatment Program Serving Small Urban and Rural Communities

“…Comorbid depressive, trauma-related, and anxiety disorders, while less consistent risk factors for worse treatment outcomes ( 1 , 5 , 6 ), necessitate assessment and integrated approaches. These are especially urgent considering people with comorbid substance use and affective disorders are at high risk for fatal overdose people compared to those without comorbid disorders ( 7 ). While facilities providing methadone in the United States, formally called opioid treatment programs (OTPs), are required to provide substance use counseling or behavioral therapies in conjunction with medication treatment ( 8 ), there is no specific requirement for those counseling services to address co-occurring affective disorders ( 9 ).…”