Clinical research that uses adopted children or adults as subjects. Sir Francis Galton was the first researcher to undertake adoption studies, in about 1876, and many researchers since then have undertaken such studies. Galton also introduced the use of TWIN STUDIES to determine the impact of heredity on individuals versus that of environment.
Adopted individuals are generally compared with nonadopted persons in a clinical or general population. Sometimes adopted adults or children are compared to adults or children in their birth family who were not adopted. They may also be compared to adopted but unrelated children in the adoptive family.
The largest adoption studies, based on the adoption records of thousands of subjects, have been performed in Europe, particularly in Denmark and Sweden. Often the results of these studies are extrapolated to adopted individuals in the United States.
The advantage of adoption studies is that they can help to illustrate the impact of both environment and heredity on a variety of issues. (See also GENETIC PREDISPOSITIONS, ADOPTED ADULTS.) Since adopted children are not reared by their biological parents, it's easier to compare similarities and differences to the birth family than it is when children are reared by their biological parents and the impact of heredity and environment is far murkier.
A key disadvantage is that researchers often fail to differentiate between individuals who were adopted as healthy infants from individuals who were not healthy at birth or were adopted at much older ages. This is of particular concern because children adopted later in their lives have often been abused, neglected or abandoned. Intermingling these populations confuses the results of the research. As a result, any time an adoption study is consulted, it is important to review whether the age and condition of the subjects at the time of the adoption have been noted as well as to look at the percentage of children or adults in the study who were about the same age at placement.
Some researchers have mounted longitudinal (long-term) studies of adopted individuals; for example, the Colorado Adoption Study of adopted individuals from early childhood onward, which took an in-depth review every few years. Studies conducted by Rita Simon and Howard Altstein on children adopted in TRANSRACIAL ADOPTIONS were also longitudinal. But because such studies are expensive and it is difficult to stay in touch with subjects over many years, most researchers study their subjects at a single point in time.
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©2000 by Christine Adamec and William Pierce, Ph.D. Reprinted from The Encyclopedia of Adoption, 2nd Edition (2nd Edition) with permission of Facts On File, Inc.