A behavioral-genetic perspective on children of alcoholics

Abstract

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 behavioral-genetic 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.

Figure 1

Contributions of genetic (G), shared—or common—environmental (C), and nonshared environmental (E) factors to the resemblance in phenotype (i.e., observable characteristics) between parents and offspring in intact nuclear and adoptive families. (A) In intact nuclear families, both genetic and shared environmental factors can contribute to parent-offspring resemblance with respect to a phenotype, such as alcoholism. (B) In adoptive families, genetic factors contribute to the resemblance between the offspring and the biological parents, whereas shared environmental factors contribute to the resemblance between the offspring and the adoptive parents.

Figure 2

Rates of severe type I (i.e., late-onset) alcoholism among male participants in two adoption studies performed in Stockholm and Gothenburg, Sweden. Both the genetic (G) and the environmental (E) backgrounds of the adoptees were classified as either high or low risk based on multiple biological and environmental factors (e.g., the presence of type I alcoholism in the biological parents or the socioeconomic status of the adoptive family). Both studies found significantly elevated rates of severe type I alcoholism only among male adoptees who both had a high genetic risk and were reared in a high-risk environment. SOURCE: Adapted from Sigvardsson et al. 1996.