Twin Studies in Psychiatry and Psychology: Science or Pseudoscience?

Twin Studies in Psychiatry and Psychology: Science or Pseudoscience? Twin studies are frequently cited in support of the influence of genetic factors for a wide range of psychiatric conditions and psychological trait differences. The most common method, known as the classical twin method, compares the concordance rates or correlations of reared-together identical (MZ) vs. reared-together same-sex fraternal (DZ) twins. However, drawing genetic inferences from MZ–DZ comparisons is problematic due to methodological problems and questionable assumptions. It is argued that the main theoretical assumption of the twin method—known as the “equal environment assumption”—is not tenable. The twin method is therefore of doubtful value as an indicator of genetic influences. Studies of reared-apart twins are discussed, and it is noted that these studies are also vulnerable to methodological problems and environmental confounds. It is concluded that there is little reason to believe that twin studies provide evidence in favor of genetic influences on psychiatric disorders and human behavioral differences. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Psychiatric Quarterly Springer Journals

Twin Studies in Psychiatry and Psychology: Science or Pseudoscience?

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Publisher
Springer Journals
Copyright
Copyright © 2002 by Human Sciences Press, Inc.
Subject
Medicine & Public Health; Psychiatry; Public Health; Sociology, general
ISSN
0033-2720
eISSN
1573-6709
D.O.I.
10.1023/A:1012896802713
Publisher site
See Article on Publisher Site

Abstract

Twin studies are frequently cited in support of the influence of genetic factors for a wide range of psychiatric conditions and psychological trait differences. The most common method, known as the classical twin method, compares the concordance rates or correlations of reared-together identical (MZ) vs. reared-together same-sex fraternal (DZ) twins. However, drawing genetic inferences from MZ–DZ comparisons is problematic due to methodological problems and questionable assumptions. It is argued that the main theoretical assumption of the twin method—known as the “equal environment assumption”—is not tenable. The twin method is therefore of doubtful value as an indicator of genetic influences. Studies of reared-apart twins are discussed, and it is noted that these studies are also vulnerable to methodological problems and environmental confounds. It is concluded that there is little reason to believe that twin studies provide evidence in favor of genetic influences on psychiatric disorders and human behavioral differences.

Journal

Psychiatric QuarterlySpringer Journals

Published: Oct 13, 2004

References

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