An Epidemiologic Analysis of Co-Occurring Alcohol and Drug Use and Disorders: Findings from the National Epidemiologic Survey of Alcohol and Related Conditions (NESARC)

Article excerpt

The 2001-2002 National Epidemiologic Survey on Alcohol and Related Conditions (NESARC) sought to determine the prevalence of alcohol use and alcohol use disorders (AUDs), other drug use and drug use disorders (DUDS), and co-use and co-morbidity in the general adult U.S. population. Findings indicate that 5.6 percent of U.S. adults used both alcohol and drugs in the past year and that 1.1 percent had a co-morbid AUD and DUD. Alcohol use prevalence peaked between the ages of 25 and 44 and declined thereafter. The prevalence of other drug use, co-use, AUDs, DUDS, and co-morbid disorders was highest between the ages of 18 and 24 and declined steadily thereafter. Women and men showed similar trends for alcohol use, drug use, and co-use. Among ethnic/racial groups evaluated, Whites displayed the highest rates of alcohol use and American Indians/Alaskan Natives the highest rates of drug use. For AUDs, DUDS, and co-morbid disorders, rates were highest among American Indians/Alaskan Natives. The prevalence of drug use, weekly drug use, and DUDS increased with increasing levels of alcohol consumption and the presence of AUDs. The proportion of people with AUDs who had a co-morbid DUD varied considerably by drug type. These findings have important implications for the development of prevention and intervention approaches.

KEY WORDS: National Epidemiologic Survey on Alcohol and Related Conditions (NESARC; alcohol use; drug use; alcohol use disorders (AUDs); drug use disorders (DUDS); co-morbidity; prevalence; epidemiology; racial/ethnic differences; gender differences

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Numerous epidemiological studies (Grant et al. 2004) have demonstrated that alcohol use disorders (AUDs) (i.e., alcohol abuse and alcohol dependence) are widespread in the general population of the United States, with approximately 8.5 percent of adults having had an AUD in the past year. Importantly, many people suffering from AUDs also suffer from one or more other psychiatric disorders, including other drug use disorders (DUDS), mood disorders (e.g., major depression), anxiety disorders, or personality disorders (e.g., antisocial personality disorder). This co-morbidity has important implications for diagnosis and, particularly, therapy because people suffering from an AUD and other comorbid disorders may not respond as well to alcoholism treatment as people with only an AUD. (For more information on treatment of patients with co-morbid AUDs and DUDS, see the article byArias and Kranzler, pp. 155-167.)

In general, the term co-morbidity refers to the co-occurrence of two or more psychiatric disorders. Recently, however, researchers have begun to distinguish between two types of comorbidity, based on the disorders involved (Angold et al. 1999):

* Homotypic co-morbidity, which refers to the co-occurrence of disorders from the same diagnostic group, such as the co-occurrence of substance use disorders like AUDs and DUDS.

* Heterotypic co-morbidity, which refers to the co-occurrence of disorders from different diagnostic groupings, such as the co-occurrence of an AUD with a mood or anxiety disorder.

Over the past two to three decades, researchers have intensely studied the relationships between AUDs and heterotypic psychiatric disorders to determine the prevalence and underlying causes of the co-morbidity (for a review, see Petrakis et al. 2002). Much less is known about the homotypic comorbidity of AUDs and DUDS, the potential causes or mechanisms underlying this co-morbidity, and its impact on treatment seeking and treatment outcome. The existing studies nonetheless have provided valuable information on homotypic co-morbidity.

Some of this research has focused on the possible mechanisms underlying the concurrent use of alcohol and other drugs. For example, researchers have investigated the possibility of genetic and environmental risk factors that may account for part of the observed association. …