Co-occurring alcohol use disorder and schizophrenia

Alcohol Research & Health, Spring, 2002 by Robert E. Drake, Kim T. Mueser

Alcohol use disorder (AUD) is the most common co-occurring disorder in people with schizophrenia. Both biological factors and psychosocial factors are thought to contribute to this co-occurrence. Schizophrenia patients with AUD are more likely to have social, legal, and medical problems, compared with other people with schizophrenia. AUD also complicates the course and treatment of schizophrenia. KEY WORDS: comorbidity; AODD (alcohol and other drug dependence); schizophrenia; prevalence; disease susceptibility; disease course; self-medication; reinforcement; dopamine; neurotransmission; social adjustment; treatment complications; combined modality therapy; correlation analysis; literature review

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Schizophrenia is a severe and disabling psychiatric disorder characterized by persistent delusions, hallucinations, disorganized speech, disorganized behavior, and negative symptoms such as the absence of emotional expression or a lack of motivation or initiative (American Psychiatric Association [APA] 1994). Alcohol use disorder (1) (AUD) commonly co-occurs with schizophrenia. This article reviews several aspects of AUD among people with schizophrenia, including the prevalence of this co-occurrence, biological and psychosocial factors that contribute to this relationship, correlated problems dually diagnosed people experience, the effects of AUD on the course and outcome of schizophrenia, treatment issues, and public policy implications. People with schizophrenia and AUD frequently abuse other substances as well. Current understanding of contributing factors, correlated problems, effect on course of illness, and treatment implications is similar for different substances of abuse.

PREVALENCE AND CONTRIBUTING FACTORS

Schizophrenia is frequently complicated by comorbid disorders such as medical illnesses, mental retardation, and substance abuse. Substance use disorder is the most frequent and clinically significant comorbidity in this population, and alcohol is the most common substance of abuse, other than nicotine (nicotine is much more prevalent than any other substance of abuse in this population) (Cuffel 1996). Undoubtedly, the availability of alcohol and the fact that it is legal contribute to its widespread abuse among people with schizophrenia as well as in the general population. The Epidemiologic Catchment Area (ECA) study (2) found that 33.7 percent of people with a diagnosis of schizophrenia or schizophreniform disorder (a related disorder marked by the same symptoms as schizophrenia but lasting less than 6 months) also met the criteria for an AUD diagnosis at some time during their lives and that 47 percent met the criteria for any substance use disorder (excluding nicotine dependence) (Regier et al. 1990). Pa tes of substance use disorder tend to be higher among males and among people of both genders and all ages in institutional settings, such as hospitals, emergency rooms, jails, and homeless shelters. This holds true for people with and without schizophrenia (Regier et al. 1990).

The high rates of AUD and other substance use disorders in people with schizophrenia appear to be determined by a complex set of factors (described below) (Mueser et al. 1998). People with schizophrenia probably use alcohol and other drugs for many of the same reasons as others in society, but several biological, psychological, and socioenvironmental factors have been hypothesized to contribute to this population's high rates of substance use disorders.

Biological Factors

There are three possible biological factors. First, many clinicians and researchers have asserted that people with schizophrenia use alcohol and other drugs to self-medicate in an attempt to alleviate the symptoms of schizophrenia or the side effects of the antipsychotic medications prescribed for schizophrenia (Chambers et al. 2001). Research evidence does not strongly support this view, however. For example, alcohol abuse often precedes schizophrenia; specific drugs of abuse are not selected in relation to specific symptoms; and various substances of abuse produce a range of different effects but generally exacerbate rather than relieve symptoms of schizophrenia (Chambers et al. 2001).

Second, the underlying neuropathological abnormalities of schizophrenia (i.e., the abnormalities in the brain that characterize schizophrenia) are thought to facilitate the positive reinforcing effects of substance use (Chambers et al. 2001). A common neurological basis for schizophrenia and for the reinforcing effects of substance use may predispose people to both conditions. This common basis involves the dysregulation of the brain chemical (i.e., neurotransmitter) dopamine. This would explain why people with schizophrenia prefer drugs such as nicotine and a class of antipsychoric medications that increase dopamine transmission in some areas of the brain. Of course, the reinforcing effects of alcohol use involve multiple neurotransmitter systems, and the mechanisms at work are not yet clear (Koob and Roberts 1999). The neurobiology of schizophrenia is similarly unclear (Chambers et al. 2001).