Prevalence and Correlates of Cannabis Use in Outpatients with Serious Mental Illness Receiving Treatment for Alcohol Use Disorders
Jordan Skalisky, Emily Leickly, Oladunni Oluwoye, Sterling M. McPherson, Debra Srebnik, John M. Roll, Richard K. Ries, and Michael G. McDonell
Cannabis and Cannabinoid Research, 2017, 2, (1), 133-138
Introduction : People with serious mental illness (SMI) use cannabis more than any other illicit drug. Cannabis use is associated with increased psychotic symptoms and is highly comorbid with alcohol use disorders (AUDs). Despite the national trend toward decriminalization, little is known about the prevalence, correlates, and impact of cannabis use on those with SMI receiving treatment for substance use disorders, a group at high risk for the negative effects of cannabis use.
Methods : In this secondary data analysis, cannabis use prevalence, correlates, and impact on treatment outcomes were examined in 121 adults with cooccurring SMI and AUDs receiving outpatient addiction treatment in a randomized trial of contingency management (CM) for alcohol. Prevalence and frequency of cannabis use were calculated across the 7-month study period using self-report and urine tests. Cannabis users were compared with nonusers by SMI diagnosis, psychiatric symptoms, medical problems, legal problems, and HIV-risk behavior. The relationship between cannabis use and longest duration of alcohol abstinence in participants randomized to CM (n = 40) was assessed.
Results : Fifty-seven (47%) of participants submitted at least one cannabis-positive urine sample during the study. Out of the 2834 total samples submitted, 751 (27%) were positive for cannabis. Cannabis users were 2.2 times more likely to submit an alcohol-positive sample, and 2.5 times more likely to submit a cocaine-positive sample at baseline, relative to noncannabis users ( p = 0.01). Cannabis users were more likely to engage in risky sexual behavior ( p = 0.01) and to report being homeless ( p = 0.03) than nonusers. When controlling for pretreatment alcohol use, the relationship between comorbid cannabis use and alcohol abstinence during CM was not significant ( p = 0.77).
Conclusion : Rates of comorbid cannabis use were high in this sample of adults with SMI and AUDs. Cannabis use was correlated with recent alcohol and cocaine use, risky sexual behavior, and homelessness, but not with alcohol abstinence during CM.
Keywords : alcohol use disorders; cannabis; contingency management; serious mental illness
Alcohol and cannabis are among the most commonly used substances worldwide.1 Within the United States, 136 million adults reported alcohol use and 20.5 million reported cannabis use in the past 30 days.2 Cannabis use and alcohol use disorders (AUDs) are highly comorbid. Cannabis users are 32% more likely than nonusers to have persistent AUDs.3 In the National Epidemiologic Survey on Alcohol and Related Conditions, 40% of adults with AUDs reported cannabis use in the past 12 months.4 Co occurring cannabis and alcohol use is associated with increased aggressive behavior, interactions with the criminal justice system, and physical health problems.5 Studies investigating the impact of comorbid cannabis use on the treatment of alcohol and other drugs have been inconclusive.6–8 Adults with serious mental illness (SMI), defined as recurring major depressive, bipolar, and schizophrenia spectrum disorders, have a lifetime prevalence of cannabis use twice as high as that of the general population.9–11
Unfortunately, nearly 50% of adults with SMI will be diagnosed with an AUD during their lifetime.12 Adults with SMI and AUDsmay be at a greater risk of negative consequences of co-occurring cannabis and alcohol use. Cannabis use is associated with more persistent psychotic symptoms, such as increased hallucinations, and alcohol use is associated with increased risk of HIV infection, homelessness, incarceration, and intentional and unintentional self-harm.1,9,13,14
Less is known about the prevalence and impact of comorbid cannabis and alcohol use in adults with SMI. One study of youth at high risk for psychosis found that although cannabis use disorders were associated with increased risk of developing psychosis, alcohol use moderated this relationship, suggesting that assessing comorbid alcohol and cannabis use may be important when understanding the relationship between substance use and the onset of psychosis.15 Given the high prevalence of cannabis and alcohol use in adults with SMI, as well as previous inconclusive findings regarding the impact of comorbid cannabis use on alcohol and other drug treatment outcomes among populations without SMI, research is needed to better understand the frequency, severity, correlates, and impact of cannabis use on outcomes in adults with SMI.
Understanding the prevalence, correlates, and relationship of cannabis use with alcohol use and illicit substances in individuals with SMI is of increasing importance. As of April 2017, 29 states and the District of Columbia have legalized medical use of cannabis. Therefore, the objectives of this study were to determine the prevalence and frequency of cannabis use, demographic and clinical correlates of cannabis use, and the relationship between cannabis use and alcohol treatment outcomes in adults with AUDs and SMI.