Purpose: Over the past 30 years, the criminal justice system has become a repository for a large number of individuals with serious mental illnesses (SMI), such as schizophrenia and bipolar disorder. Although many factors account for this trend, such as the closing of psychiatric hospitals and homelessness, an additional factor is the high rate of substance use disorders among individuals with SMI. Studies of the mediating effect of substance use on the association between SMI and criminal involvement have consistently found that substance use increases arrest risk. These studies have, however, focused on schizophrenia and on violent offenses such as assault. As the epidemiological data suggest that persons with many types of SMI are arrested for many kinds of offenses, we wanted to determine the generality of the mediating effect of substance use. Our hypothesis was that substance use disorders increase the risk for arrest among those with an SMI regardless of the class of disorder or offense.

Methods: We analyzed data from the 2002 National Household Survey on Drug Use and Health (NSDUH) for participants 18 years of age or older (N = 36,370). SMI and substance use were the main independent variables in our statistical models while past-year arrest was the dependent variable. SMI was measured through responses to the Composite International Diagnostic Interview Short Form (CIDI-SF), which allowed for classification of respondents as having a psychotic disorder, bipolar disorder, major depressive episode, generalized anxiety disorder, post-traumatic stress disorder, simple phobia or social phobia. Past-year use and dependence on alcohol or other drugs were based on responses to DSM-IV diagnostic questions. Self-reported past-year arrests were classified as violent or non-violent based on arrest charge. For each psychiatric disorder and offense type, we ran two binary logistic regressions: one with and one without variables representing substance use and dependence. All models included demographic covariates, used weighted data, and controlled for stratification and clustering. The seemingly unrelated estimates procedure in Stata was used to compare changes in the coefficients for SMI across corresponding logistic models with and without the substance use variables.

Results: Having an SMI increased the odds of being arrested for both a violent and non-violent offense though the odds ratios were higher (OR = 4.8 to 2.4) for violent as compared with non-violent offenses (OR = 3.4 to 1.1). Substance use and dependence were also generally associated with increased risk for arrest and significantly but in most cases, not completely, reduced the magnitude of the increased risk of arrest associated with having an SMI for violent offenses (OR = 3.2 to 1.8) and for non-violent offenses (OR = 1.7 to 0.8).

Implications: Those with SMI are more likely to be arrested if they also use alcohol or other drugs, regardless of diagnosis or offense type. Substance use appears to be an important but not the sole factor contributing to the “criminalization” of the mentally ill. Screening and treatment for substance use disorders among offenders with SMI should be routine to more effectively reduce criminal recidivism.