Do individuals with a severe mental illness experience greater alcohol and drug-related problems? A test of the supersensitivity hypothesis.

The supersensitivity hypothesis posits that individuals with a severe mental illness (i.e., schizophrenia and bipolar disorder; SMI) are more likely to be diagnosed with a substance abuse as opposed to a substance dependence diagnosis, and experience greater negative consequences associated with substance use at lower levels of consumption, as compared with non-SMI substance abusers. This is the first known study to test this hypothesis with a control group of non-SMI substance abusing individuals. Forty-two individuals with only a substance use disorder (SUD-only) and 53 dually diagnosed individuals (DD) were compared on measures of substance use, alcohol and drug dependence, negative consequences, substance use outcome expectancies, and motivation for change. A third group of SMI-only individuals (i.e., no SUD; n=35) were also recruited and all three groups were compared on psychological symptoms. Substance use, negative consequences, substance use outcome expectancies, motivation for change, and severity of alcohol and drug dependence were not found to differ significantly between the DD and SUD-only groups. However, the DD group had significantly greater levels of psychological symptoms, as compared with the SMI-only and SUD-only groups. Overall, this study does not provide support for the supersensitivity hypothesis.