Elsevier

Schizophrenia Research

Volume 35, Supplement 1, 1 March 1999, Pages S93-S100
Schizophrenia Research

Dual diagnosis of substance abuse in schizophrenia: prevalence and impact on outcomes

https://doi.org/10.1016/S0920-9964(98)00161-3Get rights and content

Abstract

Comorbid substance abuse disorders have emerged as one of the greatest obstacles to the effective treatment of persons with schizophrenia. Estimates of the prevalence of such comorbidity vary, but as many as half of persons with schizophrenia may suffer from a comorbid drug or alcohol disorder. Younger age, male gender, and lower educational attainment are associated with greater risk for addiction. Persons with schizophrenia and comorbid addiction tend to have an earlier onset of schizophrenia than do those without comorbid addiction. Research does not support a link between specific symptoms of schizophrenia and choice of abused drugs. Rather, drug choice is correlated with the pattern of ambient drug use in the community. Comorbid substance disorders are associated with a variety of poorer outcomes, including increased psychotic symptoms, poorer treatment compliance, violence, housing instability and homelessness, medical problems (including human immunodeficiency virus infection), poor money management, and greater use of crisis-oriented services that result in higher costs of care. Considerable progress has been made over the past decade in understanding the need to integrate substance abuse treatment and mental health treatment to provide more effective care for this population.

Introduction

Comorbid substance abuse disorders have emerged as one of the greatest obstacles to the effective treatment of persons with schizophrenia. The current treatment system often fails persons with these two disorders because of the fragmented and sometimes conflicting approaches of the mental health and substance abuse care systems. Deinstitutionalization of persons with schizophrenia, with their subsequent exposure to drugs in the community, and the wider availability of drugs such as crack cocaine may account, in part, for the urgency to develop effective treatments for persons with schizophrenia who have a comorbid drug or alcohol addiction. The development of effective treatments requires a thorough understanding of both the risk factors for the development of a comorbid substance use disorder and the consequences of substance use.

Section snippets

Epidemiology

The proportion of schizophrenic patients with a comorbid drug and/or alcohol use disorder varies tremendously in published studies from as low as 10% to as high as 70% (Mueser et al., 1990). The observed range is the result, in part, of variability in how patients are diagnosed with schizophrenia, subject characteristics, the types of populations studied (e.g. inpatient vs. outpatient, clinical vs. nonclinical), and different ways of defining drug and alcohol disorders (e.g. DSM-III-R

Types of substance abuse among persons with schizophrenia

Are there specific patterns to the types of drugs that persons with schizophrenia abuse? A corollary of the self-medication hypothesis is that persons with schizophrenia select specific drugs to counteract specific symptoms of schizophrenia and/or medication side effects. Identification of such patterns would suggest possible treatments. An alternative hypothesis is that the choice of abused substances arises primarily from availability and the ambient drug use pattern in the person's

Demographic and clinical predictors of substance use disorders

Diversity of studies has led to some inconsistencies in characterizing persons with schizophrenia who abuse drugs and/or alcohol. The most consistent findings with regard to demographic characteristics are that younger persons and men are more likely to abuse drugs and/or alcohol than are older persons and women. Mueser et al. (1990)also reported lower educational levels among persons with a substance abuse disorder and severe mental illness. Although the phenomenon of the `young male chronic

Impact of substance use disorders on course of illness and outcomes

Attempts to understand the impact of drug and alcohol use on course of illness and outcomes have produced variable results. The diversity of findings is not surprising, considering the range of research designs used. It is important to note that for many of these outcomes, it is difficult to assess the impact of one drug versus another (given the tendency toward use of multiple drugs at one time) and to assess the impact of moderate versus severe substance use disorders. However, the

Conclusion

The vulnerability of persons with schizophrenia and other serious and persistent mental disorders to substance use is clear. The extent of excess risk, the type and severity of substance use disorders, and the adverse consequences vary across geographic and treatment settings and among different demographic groups. However, persons with dual disorders are vulnerable to a related constellation of problems, including more severe psychotic symptoms, violence, noncompliance with treatment and

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