Serious Mental Illness in Heavy Drinkers Is Associated with Poor Treatment Outcomes in Outpatients with Co-occurring Disorders

The objective of this study was to determine whether the interaction between type of serious mental illness (SMI) and pre-treatment drinking severity, assessed by ethyl glucuronide (EtG), predicts EtG-positive urine samples submitted during treatment in outpatients with co-occurring alcohol dependence and SMI. Seventy-nine participants were randomized to treatment-as-usual or treatment-as-usual and contingency management (CM) targeting alcohol abstinence. Generalized estimating equations were used to assess the interaction of pre-treatment drinking (heavy drinking or light drinking) and SMI diagnosis (major depression, bipolar, or schizophrenia-spectrum disorders) across a 12-week treatment period. In the overall sample, the interaction of drinking severity and SMI diagnosis (p = 0.006) was associated with alcohol abstinence. Exploratory analyses of the interaction term among participants randomized to CM (n = 40; p = 0.008) were associated with alcohol abstinence during CM. Type of SMI diagnosis was associated with treatment outcomes in individuals who engaged in heavy drinking, but not light drinking, prior to treatment.