Models of intervention and care for psychostimulant users, 2nd edition - monograph series no. 51

Prevalence of comorbid psychiatric conditions and substance use

Page last updated: April 2004

Both epidemiological catchment area studies and clinical studies indicate that there are high rates of comorbid psychiatric problems among people with substance use problems. Epidemiological surveys conducted in North America such as the Epidemiological Catchment Area study and the National Comorbidity Survey found that substance use disorders were twice as likely to co-occur amongst people who also had a psychiatric diagnosis. Conversely, psychiatric disorders were three times more likely to co-occur in people with a substance use disorder compared to those without such a disorder (see Sinha & Schottenfeld, 2001 for a review). People with severe mental illness such as schizophrenia or bipolar disorder are at greatest risk of having a comorbid substance use disorder. For example, alcohol use disorders, such as alcohol dependence, abuse and hazardous and harmful use, affect approximately 30-40% of people diagnosed with schizophrenia (Regier, Farmer, Rae & Myers, 1993), with recent Australian data reporting a lifetime prevalence of up to 48% (Fowler, Carr, Carter & Lewin, 1998). The use of illicit drugs such as cannabis and psychostimulants such as amphetamines and cocaine is also higher amongst young adults with severe mental illness compared to either the general population or to other psychiatric comparison groups (Degenhardt & Hall, 2001; Degenhardt, Hall & Lynskey, 2001; Regier et al., 1993).

In the following section, comorbid disorders have been broadly classified into three major groups: psychotic disorders; mood disorders; and anxiety disorders. Each of these three selected diagnostic groups will be discussed in terms of presentation, clinical course and pharmacological management. A comprehensive review of effective psychosocial treatments for psychostimulant users has been presented in Chapter 5: Psychosocial interventions.