Drug and Alcohol Dependence

a b s t r a c t Background: Severe mental illness is often exclusionary criteria for studies examining factors that influ- ence addiction treatment outcome. Therefore, little is known about predictors of treatment response of individuals receiving psychosocial treatments for addictions who suffer from co-occurring severe mental illness. Methods: The impact of demographic, substance abuse severity, psychiatric severity, and service utiliza- tion variables on in-treatment performance (i.e., longest duration of abstinence) in a 12-week contingency management (CM) intervention for stimulant abuse in 96 severely mentally ill adults was investigated. A 4-step linear regression was used to identify independent predictors of in-treatment abstinence. Results: This model accounted for 37.4% of variance in the longest duration of abstinence outcome. Lower levels of stimulant use (i.e., stimulant-negative urine test) and psychiatric severity (i.e., lower levels of psychiatric distress), as well as higher rates of outpatient treatment utilization at study entry were independently associated with longer duration of drug abstinence. Conclusion: These data suggest that individuals with low levels of stimulant use and psychiatric severity, as well as those actively engaged in services are most likely to succeed in a typical CM intervention. For others, modifications to CM interventions, such as increasing the value of reinforcement or adding CM to evidence based psychiatric interventions may improve treatment outcomes.