Adoption study

I The occurrence of MDD shows a familial pattern because first-degree relatives of MDD patients are about three times more likely to develop MDD compared with first-degree relatives of normal control individuals. Adoption studies and twin studies reveal that the familial aggregation of MDD is due to genetic influences.5... 

Twin, family and adoption studies have provided compelling evidence that there is genetic as well as environmental risk for developing alcoholism. Genetic and environmental factors contribute approximately equal proportions to risk in both men and women [1],... 

The family environment, such as communicational deviancy, is unlikely to contribute to risk, because adoption studies indicate that the risk for schizophrenia in offspring of schizophrenics (i.e. first degree relatives) is unchanged by being adopted into and raised in a family without schizophrenia. Nevertheless, adverse family environments characterized by high levels of expressed emotions negatively affect the course of schizophrenia for those who are already symptomatic. 

My second example is just as egregious in its own way. White (1982), in what is otherwise an exemplary and still valuable meta-analysis, discusses the use of SES both as a spurious influence (covariate or nuisance variable) and as a causal agent (p. 462). He completely fails to warn the reader, however, that it is mandatory to sort correlations into those based on relationships between biological relatives and those based on relationships between adopted parents and their adopted children. His failure to discuss such a critical issue is perplexing as he does cite two classic adoption studies (Burks, 1928a Freeman, Holzinger, Mitchell, 1928) but not that of Scarr and Weinberg published in 1978. 

NATURE VERSUS NURTURE TWIN AND ADOPTION STUDIES... 

I Twin and adoption studies are performed to determine the relative effects of genetiG and environment I on diseases. 

No specific genetic abnormality has yet been identified, but it is clear that BPAD runs in families. Twin and adoption studies have confirmed that this family-based risk is primarily genetic in origin. 

Twin, family, and adoption studies have suggested that heritable factors are important in the development of... 

Cross-fostering adoption studies have similarly demonstrated support for a genetic contribution to risk for developing alcohol or drug abuse problems. In an examination of 913 women adopted by nonrelatives at an early age Bohman and colleagues (1981) found a... 

Cadotet, R.J., Ttougbton, E., O Gorman, T.W., and Heywood, E. (1986) An adoption study of genetic and environmental factots in drag abuse. Arch Gen Psychiatry 43 1131-1136. 

Wahiberg KE, Wynne LC, Oja H, et al. Gene-environment interaction in vulnerability to schizophrenia findings from the Finnish Adoptive Study of Schizophrenia. Am J Psychiatry 1997 154 355-362. 

The evidence available from family, twin, and adoption studies supports the existence of genetic factors in the development of primary mood disorders. 

Mendlewicz J, Rainer JD. Adoption study supporting genetic transmission in manic-depressive illness. Nature 1977 268 327-329. 

Genetic studies (primarily derived from population, family, twin, and adoptive studies) suggest that certain depressive disorders may have a genetic loading, especially bipolar and imipolar depression. 

Family, twin, and adoption studies have shown the effect of genetic factors in the affective disorders. Some evidence is seen of at least two distinct subgroups, one X-linked and the other transmitted on chromosome 11 (12-18). Reevaluation of the data by the original authors after additional clinical information became available has led to their modification of the conclusions (19). Clinical correlates of the genetic linkage have been reviewed recently (20, 21) and the codistribution of blood groups was also studied (22). 

Collectively, when Murray s findings are teamed with recent advances from biometrically informative twin and adoption studies, the causal significance of SES, for most environments found in industrialized societies, becomes attenuated further. It also motivates the necessity of more general scientific tools. 

Brody I disagree with Arthur Jensen the heritability of g itself is additive. In adoption studies involving children who have been adopted for long periods, such as in the Colorado study, by the time the adoptees get to age 15 or 16, the biological parent—child correlations run close to 0.3. There is some restriction of range in that study. At age 16 peak heritability probably hasn t been reached, so if you double that you re beginning to get estimates that are very close to what... 

Harnad Why an adoption study It is not the IKung s genetics that is of interest here it is their environment. 

Dickens WT, Flynn JR 2000 Heritability vs. environmental effects. Psychol Rev, in press Duyme M, Dumaret A-C, Tomkiewicz S 1999 How can we boost IQs of dull children A late adoption study. Proc Natl Acad Sci USA 96 8790—8794 Jensen AR 1973 Educability and group differences. Methuen, London Rushton JP 1995 Race, evolution and behavior. Transaction, New Brunswick, NJ Rutter M, Smith DJ (eds) 1995 Psychosocial disorders in young people time trends and their causes. Wiley, Chichester... 

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