Adoption Studies

Abstract

Researchers use adoption studies to determine the contributions of genetic and environmental factors to the development of alcohol problems. These studies generally compare the outcomes of adoptees who have biological parents with alcohol problems and who grow up in various adoptive environments with the outcomes of adoptees without such family backgrounds but raised in similar environments. Using certain statistical approaches, adoption studies also allow for the evaluation of specific gene-environment interactions in determining an outcome such as alcoholism. To obtain data that allow meaningful and generalizable conclusions, however, scientists must select a representative group of study subjects, obtain valid information about these subjects from a wide variety of sources, and consider biases inherent in adoption practices.

Keywords: AODR (alcohol and other drug related) problems; adoption study; behavioral problem; environmental factors; gene; hereditary factors; research and evaluation method.

Diagram showing sources of factors that affect adoptee outcome.

Figure 1

An example of an adoption study using the adoptees’ study method comparing two groups of adoptees: index adoptees and control adoptees.

Figure 2

Results of an adoptees’ study method adoption paradigm based on 160 male adoptees and their biological and adoptive families assessed for alcoholism, antisocial personality disorder, and other psychological parameters. The numbers next to the arrows are odds ratios.¹ (For example, an adoptee with first- or second-degree biological relatives with alcohol problems is 4.6 times more likely to abuse alcohol than an adoptee without such a family background.) ^*p < 0.05 ^**p < 0.01 ^***p < 0.001 ¹An odds ratio is a measure of association between two variables. SOURCE: Adapted from Cadoret et al. 1987.

Figure 3

Correlation between antisocial personality disorder in a birth parent, adverse environmental factors in the adoptive home (i.e., marital, legal, psychiatric, or substance abuse problems in the adoptive parents), and adolescent aggressivity in the adoptee. If a birth parent has an antisocial personality, a positive correlation exists between adverse environmental factors and aggressivity symptoms in the adoptee. This correlation is significantly different when none of the birth parents has an antisocial personality. SOURCE: Adapted from Cadoret et al. 1995.