Concurrent alcohol and tobacco dependence: mechanisms and treatment

Alcohol Research & Health, Spring, 2002 by David J. Drobes

People who drink alcohol often also smoke and vice versa. Several mechanisms may contribute to concurrent alcohol and tobacco use. These mechanisms include genes that are involved in regulating certain brain chemical systems; neurobiological mechanisms, such as cross-tolerance and cross-sensitization to both drugs; conditioning mechanisms, in which cravings for alcohol or nicotine are elicited by certain environmental cues; and psychosocial factors (e.g., personality characteristics and coexisting psychiatric disorders). Treatment outcomes for patients addicted to both alcohol and nicotine are generally worse than for people addicted to only one drug, and many treatment providers do not promote smoking cessation during alcoholism treatment. Recent findings suggest, however, that concurrent treatment for both addictions may improve treatment outcomes. KEY WORDS: comorbidity; AODD (alcohol and other drug dependence); alcoholic beverage; tobacco in any form; nicotine; smoking; genetic linkage; cross-tolerance; A OD (alcohol and other drug) sensitivity; neurotransmitters; brain reward pathway; cue reactivity; social AODU (AOD use); cessation of AODU; treatment outcome; combined modality therapy; literature review

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Alcohol consumption and tobacco use are closely linked behaviors. Thus, not only are people who drink alcohol more likely to smoke (and vice versa) but also people who drink larger amounts of alcohol tend to smoke more cigarettes. Furthermore, patients diagnosed with dependence on one of the drugs also are commonly diagnosed with dependence on the other drug (e.g., Zacny 1990). In fact, smoking rates among alcoholics have been estimated to be as high as 90 percent, with approximately 70 percent of alcoholics smoking at least one pack of cigarettes per day (National Institute on Alcohol Abuse and Alcoholism 1998). Similarly, smokers are far more likely to consume alcohol than are nonsmokers, and smokers who are dependent on nicotine have a 2.7 times greater risk of becoming alcohol dependent than nonsmokers (e.g., Breslau 1995). Finally, although the smoking rate in the general population has gradually declined over the past three decades, the smoking rate among alcoholics has remained persistently high (e.g., Hays et al. 1999).

Concerns about the concurrent use of alcohol and tobacco are particularly salient given the detrimental impact of this drug combination on the individual and on society. For instance, alcohol and tobacco when used together increase the risk of various forms of cancer (e.g., mouth and esophageal cancer), as well as cardiovascular disease, more than use of either drug alone (e.g., U.S. Department of Health and Human Services 1989). The concurrent use of both drugs by pregnant women can also result in more severe prenatal damage and neurocognitive deficits in their offspring than use of either drug alone (e.g., Martin et al. 1997). Furthermore, the combined use of alcohol and tobacco among adolescents is more predictive of illicit drug use and various personal and social problems among this population than use of either drug alone (e.g., Hoffman et al. 2001).

Given the frequent occurrence and broad implications of concurrent alcohol and tobacco use, research and clinical efforts clearly must focus on people who abuse both drugs. Over the past decade, interactions between alcohol and tobacco have indeed received growing attention from both basic and clinical researchers. Alcohol dependence and smoking, individually and in combination, are complex forms of addictive behavior that may be influenced by a variety of genetic, neurobiological, conditioning, and psychosocial mechanisms, as described in this article. In addition to these mechanisms, the article discusses issues related to the treatment of alcoholic smokers. This overview will necessarily be selective; for instance, there is little mention of sociocultural (e.g., economic and demographic) factors that also may contribute to concurrent use of alcohol and tobacco (see Bobo and Husten 2000).

MECHANISMS UNDERLYING COMBINED ALCOHOL AND TOBACCO USE

Genetic Factors

The importance of genetic influences on both alcoholism and smoking has gained widespread recognition over the past decade. Using behavioral genetic methods, such as twin and adoption studies, as well as genetic epidemiological approaches, researchers have established that both alcoholism and smoking have strong heritable components (e.g., Prescott and Kendler 1995). In general, heritability, which estimates the proportion of variability within an observed characteristic that can be attributed to genetic factors, appears to be slightly higher for smoking-related variables (e.g., smoking initiation and smoking persistence) than for alcoholism (e.g., Heath and Madden 1995). Moreover, several researchers have indicated that a substantial shared genetic risk exists between smoking and alcoholism--that is, genetic factors that increase the risk for smoking also increase the risk for alcoholism and vice versa (e.g., Koopmans et al. 1997; Prescott and Kendler 1995).