Children inherit many traits from their birthparents including eye color, hair color, potential physical build, potential talents and others. In addition, children may also inherit propensities to certain genetically transmitted diseases, such as diabetes or Huntington's disease. A genetic predisposition means that a person may exhibit a trait but also may not. Behavioral characteristics are thought to stem from the confluence of heredity and environment. Neither should be denied its importance.
Children may also inherit predispositions to talents or abilities. For example, if a birthmother has musical talent, then her son, now adopted, might have a genetic predisposition to musical ability. On the other hand, it is also true that this genetic predisposition may never present itself as an ability. Despite being exposed to music lessons in an adoptive home, the child may have no talent or interest in music.
Individually, genetic predispositions may seem "good" or "bad." However, their characteristics are often expressed in negative terms when it comes to adoption. When scientists study populations of adopted children and adults, they often look at social problems such as alcoholism, drug abuse and so forth. This research bias makes it seem as if these characteristics are the only or the most important aspects of adoption. Rarely, if ever, do researchers analyze whether the "good" aspects of the biological parents are later evidenced in their children who were adopted. Studies of twins separated at birth and studies of adopted children and their birth and adoptive families have revealed a variety of possible inherited predispositions.
Adoptive parents may fear that the tendency to develop some psychiatric ailments, such as schizophrenia, may be genetically transmitted, especially given the coverage by the popular press on wrongful adoption lawsuits.
In a comprehensive article on the genetic factors related to psychiatric disorders reported in the Journal of Child Psychology and Psychiatry, the authors reported on a study that found a correlation between schizophrenia in siblings. The study by Kety, Rosenthal, Wender, Schulsinger and Jacobsen in 1975 found "13% of paternal half-siblings of adopted schizophrenics, compared with only 2% of control half-siblings, were diagnosed as being schizophrenic."
Yet later studies revealed environment was important, and a dysfunctional family influence could also be tied to the development of schizophrenia.
Although it is generally believed that emotional disorders have a genetic component, some adoption studies have indicated that the correlation is not always clearly evident. For example, in a study reported in 1998 in the Journal of Child Psychology and Pyschiatry and Allied Disciplines, researchers sought to find a linkage between depression in adopted children and emotional problems in the biological mother.
The subjects were children in a longitudinal study known as the Colorado Adoption Project. Researchers compared 180 adopted children to their birthparents and 227 nonadopted children to their parents. To the apparent surprise of the researchers, they found "no evidence for genetic influence for depressive symptoms." They stated that these findings were in sharp contrast to findings in twin studies. They concluded, "At the very least these findings raise doubts about genetic influence on depressive symptoms in middle childhood and warrant more than usual the maxim that more research is needed."
Other genetic predispositions have been demonstrated; for example, indications of a predisposition to obesity have been shown to exist among full and half-siblings raised apart. Researchers P. Costanzo and S. Schiffman disagreed in their 1989 article for Neuroscience Biobehavior Review and argue that it is thin stature that is inherited rather than a predisposition to be obese.
Premature death of birthparents has also been correlated to premature death in their offspring. Researchers studied 960 families that included nonrelated children who had been adopted and who were born between 1924 and 1926 and computed the risk of the adopted persons' early deaths. (The researchers used data available from adopted Danes, predominantly Caucasians.)
According to their report in the New England Journal of Medicine, the researchers concluded that death from such diseases as cancer appears to be affected by the environment of the family. Premature deaths caused by infection or vascular causes, however, showed clear genetic links.
Early deaths of adoptive parents were also found to be significant to the longevity of adopted persons. If an adoptive parent died of cancer before age 50, the risk of the adopted person also dying from cancer increased by five times. This information indicates a strong environmental and lifestyle element at work in the case of cancer, for example, whether or not the adoptive parents are smokers.
Some researchers also have identified a strong heritability of general mental ability and intelligence. (See also INTELLIGENCE.)
The Colorado Adoption Project is a longitudinal study of 245 adopted children, their adoptive parents and birthparents. The children were studied at ages one, two, three, four and seven years of age.
At ages one and two, the children were given the Bayley Scales of Infant Development. At ages three and four, the Stanford-Binet Intelligence Scale-Form was administered. At age seven, the researchers used the Wechsler Intelligence Scale for Children-Revised.
The researchers reported on their findings in Nature, stating there were strong indicators of a relationship of intelligence to the birthparents, which increased as the child grew older. Apparently, adoptive parents have a strong impact on a child's intellectual level in the early years, and genetics "kick in" at a later date.
Researchers on the Texas Adoption Project, a study of children measured twice at ten-year intervals, also found an increased heritability of intelligence, a relationship that strengthened until adolescence or even adulthood.
In a longitudinal study of 100 identical twins raised apart, the Minnesota Study, the researchers found a strong correlation for intelligence and other traits; however, they do not denigrate the value of environment and good parenting skills.
There have also been studies comparing the IQ levels of children who have been adopted to their half-siblings who were raised by birthparents. A study by Schiff and Lewontin in 1986 compared the IQ levels of adopted children whose birthmothers were "socially disadvantaged" compared to the IQ levels of half-siblings raised by the birthmother. They found the adopted children scored as much as 16 points higher in IQ levels than did the siblings who remained with the birthmother.
The physical activity level of the adopted person appears to be at least partially affected by genetics. One study revealed the type of exercise was dependent on the environment; however, the overall level of the adopted person's physical activity was significantly related to the physical activity level of the birthparent.
One might conclude that instead of choosing bowling or football, an adopted child might opt for swimming or tennis or whatever sport fits in best with the socioeconomic status of the adoptive parents.
Studies Comparing Adopted Children to Nonadopted Siblings Who Remained in the Birth Home
In some studies, researchers have compared children adopted as infants to their siblings who were not adopted and who remained with the birthparents and found some commonalities and some differences. For example, the adopted children are often taller than their nonadopted siblings and have higher I.Q. as well. The adopted children had better performances in reading and math, although their performances were slightly behind those of nonadopted children in the general population.
There are both genetic and environmental components in the temperaments of adopted children. Said David Howe in his book Patterns of Adoption, "For many temperaments, adopted children are more like their biological than their adopted parents. .?. However, some traits appear to be more heritable than others. For example, sociability and openness to experience show a large genetic influence. In contrast, traits associated with agreeableness and conscientiousness show low heritability, most influences appearing to be caused by family environmental factors. Extroversion and neuroticism are influenced by both genetic inheritance and non-shared environmental experience."
Many other correlations have been found, including some surprising ones. For example, in a 1998 issue of the Annals of Allergy, Asthma & Immunology, researchers studied 367 adoptive parents from Iowa with and without asthma and their children. All the children were adults and most were in their twenties.
They found that if an adoptive mother had asthma and allergic rhinitis, the adopted child's risk for asthma increased. If the adoptive mother had only asthma or only allergic rhinitis, that too increased the risk of asthma in the adopted child. If the adoptive father had asthma or allergic rhinitis there was a trend, although a lower probability than with the mother, toward increased asthma in the adopted person.
The researchers speculated that there could be a genetic propensity to some allergies but that they might be triggered by an environmental agent, such as a virus. That could explain the increased existence of asthma in the adopted adults with mothers who had allergic rhinitis and/or asthma. The researchers did not have information on the birthparents but it seems apparent that it is very unlikely that the children were matched with their adoptive parents on the basis of whether or not their biological parents had allergic rhinitis or asthma.
Attempts to Elicit Genetic Data
Most scientists agree that both heredity and environment are important to a child's development. However, even when heredity is significant, the genetic markers cannot always be identified nor can the interaction of heredity and environment be clearly delineated.
Because some genetic predispositions can be very important to a child's future, many states require that child-placing agencies and adoption attorneys provide extensive nonidentifying medical and social information to the adoptive parents.
In addition, adopted adults in numerous studies have stated their desire for medical information, hobbies and interests of birthparents, so obviously the information would be valuable to them. Whether the adoption is a traditional confidential adoption or an open adoption, such information should be obtained from the birthparents.
It is important, however, to remember that many children who were adopted in the past, as now, did not come with this genetic and other information as part of their "passports." Orphaned children and foundlings such as the 50,000 children from Korea adopted by U.S. citizens, can make excellent adjustments despite the lack of this information.
Also, most qualified medical practitioners realize careful testing and physical examination, are balanced by knowledge of detailed medical background information in providing sound medical care for their patients. Parents should be cautious if confronted by medical or other professionals who claim they can't help or treat the parents' child without such genetic and background information. (See also ADOLESCENT ADOPTED PERSONS; ADULT ADOPTED PERSONS; GENETIC DATA; PATHOLOGY AND ADOPTIVE STATUS; PSYCHIATRIC PROBLEMS OF ADOPTED PERSONS.)
Preadoption Genetic Testing
Because of interest and concern about genetic predispositions, some adoptive families have indicated a strong interest in genetic testing. As our knowledge of genetics grows, so should our ability to obtain such data. However, one serious problem with preadoption genetic testing is that it may unfairly screen out children to be adopted. A "predisposition" is just that: a possibility, a propensity. It is not a certainty. But if genetic testing could show, for example, that the child carried a gene for a serious health problem, it is likely that child would be regarded as a child with SPECIAL NEEDS and might not be adopted at all.
In addition, even if a child with an identified particular genetic predisposition was adopted, that child might experience a variety of subtle or overt discriminations, in the family, at school or in the workplace. The child's self-esteem could also be affected quite profoundly, leading to low expectations and poor achievement, as well as in other ways. For example, diagnosis of a genetic potential may lead to an unintended outcome, such as that of adult women who, when they learned that they had a genetic predisposition to breast cancer, have insisted on a mastectomy even though there was no cancer present in the breast.
Another problem with genetic testing is the "self-fulfilling prophecy." For example, if a child and his parents believe that the child is likely to develop an emotional disorder, then the disorder may present as a result of the expectation, rather than as a result of genetics. Psychiatrists Andre Derdeyn and Charles L. Graves expressed their concern over parents who may overlay their negative expectations on adopted children based on the biological parents' attributes. Said the doctors:
"Parents' over-concern about their adopted children may contribute significantly to the family's problems. A source of this concern relates to the parents' fantasies of the behavior and personalities of the people whose union produced the child and whose imagined weakness, immorality, or instability led to the child's adoption. These ideas can lead to the construction of a defective mental portrait of the child."
And when this scrutiny occurs, say the doctors, "Parents' over-concern about problematic behavior has had its paradoxic effect, whereby the child has started to identify with the parents' expressed expectations and has started to act accordingly. Insufficient working through of the loss of the biologic child and the acceptance of the adopted child may make the parents feel underentitled to the child, undermining their confidence and their ability to set limits. Parental frustration leads to increasing hostility, which triggers the child's separation anxiety. The child typically deals with the separation anxiety in a counterphobic manner in terms of provocative behavior." In other words, the child acts out in the feared (but apparently expected) manner.
Although the doctors did not address the issue of preadoption genetic testing, it seems likely that if adoptive parents were able to obtain information about genetic predispositions for problem behaviors, they would be even more likely to watch out for such behaviors in their children.
It is also not clear that the "best interests of the child" are represented by requiring genetic testing. For a further discussion on preadoption testing, see Madelyn Freundlich's article, "The Case Against Preadoption Genetic Testing," in the November?1, 1998 issue of Child Welfare.
Thomas J. Bouchard Jr., David T. Lykken, Matthew McGue, Nancy J. Segal and Auke Tellegen, "Sources of Human Psychological Differences: The Minnesota Study of Twins Reared Apart," Science, 250 (October?12, 1990).
P. R. Costanzo and S. Schiffman, "Thinness-Not Obesity-Has a Genetic Component," Neuroscience Biobehavior Review (spring 1989): 55-58.
Andre P. Derdeyn, M.D., and Charles L. Graves, M.D., "Clinical Vicissitudes of Adoption," Child and Adolescent Psychiatric Clinics of North America 7, no. 2 (April 1998): 373-388.
Thalia C. Eley, et al., "An Adoption Study of Depressive Symptoms in Middle Childhood," Journal of Child Psychology and Psychiatry and Allied Disciplines 39, no. 3 (March 1998): 337-345.
Madelyn D. Freundlich, "The Case Against Preadoption Genetic Testing," Child Welfare 77, no. 6 (November?1, 1998): p. 663.
D. W. Fulker, J. C. DeFries, and Robert Plomin, "Genetic Influence on General Mental Ability Increases Between Infancy and Middle Childhood," Nature 336 (December 1988): 767-769.
H. H. Goldsmith, "Genetic Influences on Personality from Infancy to Adulthood," Child Development 54 (1983): 331-355.
Joseph M. Horn, "The Texas Adoption Project: Adopted Children and Their Intellectual Resemblance to Biological and Adoptive Parents," Child Development 54 (1983): 268-275.
David Howe, Patterns of Adoption: Nature, Nurture and Psychosocial Development (Oxford, England: Blackwell Science), 1998.
John C. Loehlin, Joseph M. Horn and Lee Willerman, "Modeling IQ Change: Evidence from the Texas Adoption Project," Child Development 60 (1989): 993-1004.
Harry Munsinger, "The Adopted Child's IQ: A Critical Review," Psychological Bulletin 82 (September 1975): 623-659.
Herbert Pardes, M.D., Charles A. Kaufmann, M.D., Harold Alan Pincas, M.D., and Anne West, "Genetics and Psychiatry: Past Discoveries, Current Dilemmas, and Future Directions," The American Journal of Psychiatry, April 1989, 434-443.
L. P?russe, A. Tremblay, C. Leblanc and C. Bouchard, "Genetic and Environmental Influences on Level of Habitual Physical Activity and Exercise Participation," American Journal of Epidemiology 129 (May 1989): 1012-1022.
Robert Plomin and J. C. DeFries, "The Colorado Adoption Project," Child Development 54 (1983): 276-289.
Michael Rutter, Patrick Bolton, Richard Harrington, Ann Le Couteur, Hope Macdonald and Emily Simonoff, "Genetic Factors in Child Psychiatric Disorders-I. A Review of Research Strategies," The Journal of Child Psychology and Psychiatry and Allied Disciplines 31 (January 1990): 3-37.
Michael Rutter, Hope Macdonald, Ann Le Couteur, Richard Harrington, Patrick Bolton and Anthony Bailey, "Genetic Factors in Child Psychiatric Disorders-II. Empirical Findings," The Journal of Child Psychology and Psychiatry and Allied Disciplines 31 (January 1990): 39-83.
Sandra Scarr, Patricia L. Webber, Richard A. Weinberg and Michele A. Wittig, "Personality Resemblance Among Adolescents and Their Parents in Biologically Related and Adoptive Families," Journal of Personality and Social Psychology 40 (1981): 885-898.
Sandra Scarr and Richard Weinberg, "The Minnesota Adoption Studies: Genetic Differences and Malleability," Child Development 54 (1983): 260-267.
M. Schiff and R. Lewontin, Education and Class: The Irrelevance of IQ Genetic Studies (Oxford: Clarendon Press, 1986).
Jeanne M. Smith. M.D., et al., "Asthma and Allergic Rhinitis in Adoptees and Their Adoptive Parents," Annals of Allergy, Asthma, & Immunology 81 (1998): 135-139.
Thoorkild I. A. S?rensen, R. Arlen Price, Albert J. Stunkard and Fini Schulsinger, "Genetics of Obesity in Adult Adoptees and Their Biological Siblings," British Medical Journal 298 (January?14): 1989, 87-90.
T. I. S?rensen, G. G. Nielsen, P. K. Andersen and T. W. Teasdale, 'Genetic and Environmental Influences on Premature Death in Adult Adoptees," New England Journal of Medicine" 318 (March?24, 1988): 727-732.
T. W. Teasdale and T. I. A. Sorenson, "Educational Attainment and Social Class in Adoptees: Genetic and Environmental Contributions," Journal of Biosocial Science 15 (1983): 509-518.
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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.
Note: Our authors are dedicated to honest, engaged, informed, intelligent, and open conversation about adoption. The opinions expressed here may not reflect the views of Adoption.com.