Unmet Need in Relation to Mental Healthcare and Past-Month Drug Use among People with Mental Illness in the United States.

Individuals with mental illness are at risk of developing co-occurring substance use disorders (SUDs). We assessed whether unmet need for mental health treatment in the past year was a risk factor for past-month use of marijuana, cocaine, methamphetamine, and misuse of prescription opioids in this population. Data from adults diagnosed with mental illness who were not diagnosed with SUD were examined from the 2015-2018 National Survey on Drug Use and Health (N = 33,104). An estimated 20.8% (95% CI: 20.1-21.5) of adults in the US with mental illness have experienced unmet need in the past year. Those reporting marijuana use (29.7% vs. 19.5%, p < .001) and/or prescription opioid misuse (35.7% vs. 20.5%, p < .001) were more likely to report unmet need than those not reporting use. In multivariable models, unmet need remained a risk factor for marijuana use (aOR = 1.37, 95% CI: 1.24-1.54) and prescription opioid misuse (aOR = 1.65, 95% CI: 1.29-2.13). Unmet need was not a risk factor for cocaine or methamphetamine use. Cost as a barrier to treatment was a risk factor for marijuana use (aOR = 1.37, 95% CI: 1.19-1.58) and prescription opioid misuse (aOR = 1.95, 95% CI: 1.43-2.64). Policies aimed at improving mental healthcare access may be effective in reducing substance use in this population.