Adoption Studies


Adoption studies are one form of clinical genetic study designed to evaluate genetic and environmental influences on phenotype. In adoption studies the index cases and controls are adoptees. The adoption study design provides a unique opportunity to examine gene and gene by environment interactions for a variety of behavioural, psychiatric and medical disorders. Adoption genetic studies provide some challenges related to the issues related to adoption (atypical biological parent profiles, differences in adoptive parents compared to nonadoptive parents and the stress of learning about being an adoptee). Recently, molecular genetic strategies have been applied to samples of adoptees. Advancing privacy issues have made it more difficult to design and carry out adoption research.

Key Concepts:

  • Adoption studies provide a unique research model where biological genetic effects can be estimated.

  • Adoption studies can be helpful in uncovering gene–environment interactions in complex behavioural and psychiatric disorders.

  • Adoption genetic studies utilise a variety of statistical techniques including calculation of odds ratios, logistic regression, log‐linear statistical monitoring and path analysis.

  • Recent advances in adoption study research have occurred by combining molecular genetic techniques to the genetic and environmental data of adoptees.

  • Increased privacy concerns and privacy laws related to biological parent anonymity have made adoption studies more difficult to design and implement.

Keywords: log‐linear analysis; path analysis; logistic regression; gene–environment interaction; adoption studies; selective placement

Figure 1.

Demonstration that smoking by the biological parent(s) and adoptive family contributes to adoptee smoking with biological family smoking having a stronger relationship. Adoptee smoking is associated with adoptee antisocial behaviour, a factor associated with a biological family antisocial problem. The relationship between biological family smoking and adoptive family smoking is not significant, suggesting there is no confounding by selective placement. Numbers indicate odds ratios.



Alarcon M, Plomin R, Fulker DW, Corley R and DeFries JC (1998) Multivariate path analysis of specific cognitive abilities data at 12 years of age in the Colorado Adoption Project. Behavioral Genetics 28: 255–264.

Cadoret RJ, Winokur G, Langbehn D et al. (1996) Depression spectrum disease, I: the role of gene–environment interaction. American Journal of Psychiatry 153: 892–898.

Fulker DW and DeFries JC (1983) Genetic and environmental transmission in the Colorado Adoption Project: path analysis. British Journal of Mathematical and Statistical Psychology 36: 175–188.

Klahr AM, McGue M, Iacono WG and Burt SA (2011) The association between parent–child conflict and adolescent conduct problems over time: results from a longitudinal adoption study. Journal of Abnormal Psychology 120: 46–56.

Klump KL, Suisman JL, Burt SA, McGue M and Iacono WG (2009) Genetic and environmental influences on disordered eating: an adoption study. Journal of Abnormal Psychology 4: 797–805.

Langbehn DR and Cadoret RJ (2001) The adult antisocial syndrome with and without antecedent conduct disorder: comparisons from an adoption study. Comprehensive Psychiatry 42: 272–282.

Langbehn DR, Cadoret RJ, Yates WR, Troughton EP and Stewart MA (1998) Distinct contributions of conduct and oppositional defiant symptoms of adult antisocial behavior: evidence from an adoption study. Archives of General Psychiatry 55: 821–829.

Langbehn DR, Philibert R, Caspers KM, Yucuis R and Cadoret RJ (2006) Association of a D2S2944 allele with depression specifically among those with substance abuse or antisocial personality. Drug and Alcohol Dependence 83: 33–41.

McGue M, Keyes M, Sharma A et al. (2007) The environments of adopted and non‐adopted youth: evidence on range restriction from the Sibling Interaction and Behavior Study (SIBS). Behavoural Genetics 3: 449–462.

Petersen L, Sørensen TI, Mortensen EL and Andersen PK (2010) Excess mortality rate during adulthood among Danish adoptees. PLoS One 5: e14365.

Philibert R (2006) Merging genetic and environmental effects in the Iowa Adoption Studies: focus on depression. Annals of Clinical Psychiatry 4: 219–222.

Philibert R, Caspers K, Langbehn D et al. (2003) The association of the D2S2944 124 bp allele with recurrent early onset major depressive disorder in women. American Journal of Medical Genetics part B: Neuropsychiatric Genetics 1: 39–43.

Philibert RA, Gunter TD, Beach SR, Brody GH et al. (2009a) Role of GABRA2 on risk for alcohol, nicotine, and cannabis dependence in the Iowa Adoption Studies. Psychiatry and Genetics 19: 91–98.

Philibert RA, Sandhu H, Hollenbeck N et al. (2008) The relationship of 5HTT (SLC6A4) methylation and genotype on mRNA expression and liability to major depression and alcohol dependence in subjects from the Iowa Adoption Studies. American Journal of Medical Genetics part B: Neuropsychiatric Genetics 5: 543–549.

Philibert RA, Todorov A, Andersen A et al. (2009b) Examination of the nicotine dependence (NICSNP) consortium findings in the Iowa adoption studies population. Nicotine & Tobacco Research 3: 286–292.

Phillips K and Fulker DW (1989) Quantitative genetic analysis of longitudinal trends in adoption designs with application to IQ in the Colorado Adoption Project. Behavioral Genetics 19: 621–658.

Smoller JW and Finn CT (2003) Family, twin, and adoption studies of bipolar disorder. American Journal of Medical Genetics part C: Seminars in Medical Genetics 123C: 48–58.

Sorensen TI, Holst C and Stunkard AJ (1998) Adoption study of environmental modifications of the genetic influences on obesity. International Journal of Obesity and Related Metabolic Disorders 22: 73–81.

Taylor L, Faraone SV and Tsuang MT (2002) Family, twin, and adoption studies of bipolar disease. Current Psychiatry Reports 2: 130–133.

Thornton LM, Mazzeo SE and Bulik CM (2011) The heritability of eating disorders: methods and current findings. Current Topics in Behavioural Neuroscience 6: 141–156.

Tienari P, Wynne LC, Sorri A et al. (2004) Genotype–environment interaction in schizophrenia‐spectrum disorder. Long‐term follow‐up study of Finnish adoptees. British Journal of Psychiatry 184: 216–222.

Yates WR, Cadoret RJ and Troughton EP (1999) The Iowa adoption studies: methods and results. In: LaBuda MC and Grigorenko EL (eds) On the Way to Individuality: Methodological Issues in Behavioral Genetics, pp. 95–125. Commack, NY: Nova Science Publishers.

Yates WR, Cadoret RJ, Troughton EP, Stewart M and Guinta TS (1998) Effect of fetal alcohol exposure on adult symptoms of nicotine, alcohol and drug dependence. Alcoholism: Clinical and Experimental Research 22: 914–920.

Further Reading

Christensen R (1997) Log‐linear Models and Logistic Regression. New York, NY: Springer.

Everitt BS and Dunn G (1991) Applied Multivariate Data Analysis. London, UK: Edward Arnold.

Kleinbaum DG (1994) Logistic Regression: A Self‐learning Text. New York, NY: Springer.

Kleinbaum DG, Kupper LL, Muller KE, Nizam A and Nizati A (1997) Applied Regression Analysis and Multivariate Methods. Pacific Grove, CA: Duxbury Press.

Plomin R, DeFries JC, McClearn GE and McGuffin P (2008) Behavioral Genetics. New York, NY: Worth Publishers.

Wrobel GM and Neil E (eds) (2009) International Advances in Adoption Research for Practice. Hoboken, NJ: Wiley.

Web Links

Power, Sample Size and Experimental Design Calculations.

Contact Editor close
Submit a note to the editor about this article by filling in the form below.

* Required Field

How to Cite close
Yates, William R(Jun 2011) Adoption Studies. In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1002/9780470015902.a0005422.pub2]