A behavioral-genetic perspective on children of alcoholics.

Resemblance between parents and their children with respect to certain behaviors (e.g., alcohol use) may result from shared genes or from environmental influences that affect all members of a family similarly. Behavioral geneticists have used adoption, twin, and genetic marker studies to investigate the contributions of genetic as well as shared and nonshared environmental influences to the increased risk for alcoholism in children of alcoholics (COA's). These analyses have found that in male COA's, genetic makeup (i.e., genotype) plays an important role in the development of alcoholism; in female COA's, however, the results were less consistent. Moreover, for both men and women, genetic factors alone cannot account for their risk of alcoholism. The behavioralgenetic concepts of genotype-environment interaction and genotype-environment correlation may provide useful models for the joint influences of genetic and environmental factors in the development of alcoholism. KEY WORDS: children of alcoholics; hereditary vs. environmental factors; family environment; AOD use behavior; AODU (alcohol and other drug use) development; AODD (alcohol and other drug dependence); gender differences; risk factors; AOD dependence; adoption study; twin study; genetic markers; genotype; parent; behavioral and mental disorder; scientific model; literature review Family studies have consistently demonstrated that many children of alcoholics (COA's) exhibit a wide range of characteristics associated with their parents' alcoholism.1 For example, compared with children of nonalcoholics (nonCOA's), COA's are more likely to be alcoholic themselves (Cotton 1979) and to have other behavioral and psychiatric problems (West and Prinz 1987; Sher and Trull 1994).Moreover, COA's frequently show more extreme manifestations than do non-COA's of the temperament characteristics associated with an increased risk for alcoholism (e.g., behavioral disinhibition and negative emotionality) (Sher 1991). Although the prognostic significance of parental alcoholism on COA functioning is undisputed, researchers do not yet fully understand the causes and mechanisms underlying these parent-offspring correlations. Any behavioral resemblance among members of an intact nuclear family (i.e., biological mother, biological father, and children) may result from shared genes or from the influences of their shared, or common, environment. Thus, the observation that COA's exhibit elevated rates of behavioral disorders does not indicate whether this increased risk results from the genes that alcoholic parents transmit to their children, some deficiency in the rearing environment provided by alcoholic parents, or a combination of both of these influences. Unfortunately, when interpreting findings from studies on COA's, researchers have not always taken into account this fundamental limitation of family study methods. Accordingly, biologically oriented researchers tend to interpret familial associations as reflecting biological mechanisms, whereas psychosocially oriented researchers generally consider familial associations the result of environmental mechanisms. This article reviews findings of behavioral-genetic research on alcoholism, including the results of both adoption and twin studies. These analyses indicate that genetic factors play a major role in the relationship between parental alcoholism and COA functioning. The environmental influences resulting from being reared by an alcoholic parent, in contrast, do not appear to increase the risk of alcoholism in the children. This article also discusses two models-genotypeenvironment interaction and genotype-environment correlation-that may explain how a person's genetic makeup (i.e., genotype) and environment jointly influence the person's risk of alcoholism. METHODS OF BEHAVIORAL GENETICS Behavioral geneticists distinguish three major contributors to individual differences in people's observable characteristics (i. …