Adoption Studies

Abstract

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.

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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.

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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. http://members.aol.com/johnp71/javastat.html#Power

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Yates, William R(Jun 2011) Adoption Studies. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002/9780470015902.a0005422.pub2]