Hostname: page-component-586b7cd67f-rdxmf Total loading time: 0 Render date: 2024-11-27T20:18:30.997Z Has data issue: false hasContentIssue false
  • English
  • Français

Parental treatment and the equal environment assumption in twin studies of psychiatric illness

Published online by Cambridge University Press:  09 July 2009

K. S. Kendler ,
M. C. Neale ,
R. C. Kessler ,
A. C. Heath  and
L. J. Eaves
K. S. Kendler*
Affiliation:
Departments of Psychiatry and Human Genetics, Medical College of Virginia/Virginia Commonwealth University, Richmond, Virginia; Institute for Social Research, University of Michigan, Ann Arbor, Michigan; Department of Psychiatry, Washington University School of Medicine, St Louis, Missouri, USA
M. C. Neale
Affiliation:
Departments of Psychiatry and Human Genetics, Medical College of Virginia/Virginia Commonwealth University, Richmond, Virginia; Institute for Social Research, University of Michigan, Ann Arbor, Michigan; Department of Psychiatry, Washington University School of Medicine, St Louis, Missouri, USA
R. C. Kessler
Affiliation:
Departments of Psychiatry and Human Genetics, Medical College of Virginia/Virginia Commonwealth University, Richmond, Virginia; Institute for Social Research, University of Michigan, Ann Arbor, Michigan; Department of Psychiatry, Washington University School of Medicine, St Louis, Missouri, USA
A. C. Heath
Affiliation:
Departments of Psychiatry and Human Genetics, Medical College of Virginia/Virginia Commonwealth University, Richmond, Virginia; Institute for Social Research, University of Michigan, Ann Arbor, Michigan; Department of Psychiatry, Washington University School of Medicine, St Louis, Missouri, USA
L. J. Eaves
Affiliation:
Departments of Psychiatry and Human Genetics, Medical College of Virginia/Virginia Commonwealth University, Richmond, Virginia; Institute for Social Research, University of Michigan, Ann Arbor, Michigan; Department of Psychiatry, Washington University School of Medicine, St Louis, Missouri, USA
*
1Address for correspondence: Dr Kenneth S. Kendler, Box 980710, MCV Station, Richmond, VA 23298–0710, USA
Get access Rights & Permissions [Opens in a new window]

Synopsis

The validity of the twin method depends on the equal environment assumption (EEA) – that monozygotic (MZ) and dizygotic (DZ) twins are equally correlated in their exposure to environmental factors of aetiological importance for the trait under study. Parents may treat MZ twins more similarly than DZ twins thereby potentially violating the EEA. We tested this hypothesis for four common psychiatric disorders (major depression, generalized anxiety disorder, phobia, and alcoholism) in a population-based sample of female–female twin pairs where analyses indicate sufficient statistical power meaningfully to test the EEA. Mother's and father's beliefs about their twins' zygosity disagreed with assigned zygosity in approximately 20% of cases, often because of what they were told about their twins' zygosity at their birth. By structural equation model-fitting, we found no evidence that mother's or father's perceived zygosity influenced twin resemblance for any of the disorders. Compared to parents of DZ twins, parents of MZ twins were more likely to report that, in rearing their twins, they emphasized their similarities more than their differences. However, by model-fitting, mothers' and fathers' approach to raising twins had no significant influence on twin resemblance for the four examined psychiatric disorders. These results suggest that the differential treatment of MZ and DZ twins by their parents is unlikely to represent a significant bias in twin studies of these major psychiatric disorders.

Type
Original Articles
Information
Psychological Medicine , Volume 24 , Issue 3 , August 1994 , pp. 579 - 590
Copyright
Copyright © Cambridge University Press 1994

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Akaike, H. (1987). Factor analysis and AIC. Psychometrika 52, 317–332.CrossRefGoogle Scholar
American Psychiatric Association (1980). Diagnostic and Statistical Manual of Mental Disorders, 3rd edn. American Psychiatric Association: Washington, DC.Google Scholar
American Psychiatric Association (1987). Diagnostic and Statistical Manual of Mental Disorders, 3rd edn Revised. American Psychiatric Association: Washington, DC.Google Scholar
Clifford, C. A., Hopper, J. L., Fulker, D. & Murray, R. M. (1984). A genetic and environmental analysis of a twin family study of alcohol use, anxiety, and depression. Genetic Epidemiology 1, 63–79.CrossRefGoogle ScholarPubMed
Cohen, J. (1960). A coefficient of agreement for nominal scales. Educational and Psychological Measurement 20, 37–46.CrossRefGoogle Scholar
Cunningham, F. G., MacDonal, P. C. & Gant, N. F. (1989). Williams Obstetrics. Appleton & Lange: Norwalk, CT.Google Scholar
Falconer, D. S. (1965). The inheritance of liability to certain diseases, estimated from the incidence among relatives. Annals of Human Genetics 29, 51–76.CrossRefGoogle Scholar
Galton, F. (1875). The history of twins as a criterion of the relative powers of nature and nurture. Fraser's Magazine 12, 566–576.Google Scholar
Goodman, R. & Stevenson, J. (1989). A twin study of hyperactivity. II. The aetiological role of genes, family relationships and perinatal adversity. Journal of Child Psychology and Psychiatry 30, 691–709.CrossRefGoogle ScholarPubMed
Heath, A. C., Jardine, R. & Martin, N. G. (1989). Interactive effects of genotype and social environment on alcohol consumption in female twins. Journal of Studies on Alcohol 60, 38–48.CrossRefGoogle Scholar
Hrubec, Z. & Robinette, C. D. (1984). The study of human twins in medical research. New England Journal of Medicine 310, 435–441.CrossRefGoogle Scholar
Kaprio, J., Koskenvuo, M. & Rose, R. J. (1990). Change in cohabitation and intrapair similarity of monozygotic (MZ) cotwins for alcohol use, extraversion, and neuroticism. Behavior Genetics 20, 265–276.CrossRefGoogle ScholarPubMed
Kempthorne, O. & Osborne, R. H. (1961). The interpretation of twin data. American Journal of Human Genetics 13, 320–339.Google ScholarPubMed
Kendler, K. S. (1983). Overview: a current perspective on twin studies of schizophrenia. American Journal of Psychiatry 140, 1413–1425.Google ScholarPubMed
Kendler, K. S., Heath, A. C., Martin, N. G. & Eaves, L. J. (1986). Symptoms of anxiety and depression in a volunteer twin population: the etiologic role of genetic and environmental factors. Archives of General Psychiatry 43, 213–221.CrossRefGoogle Scholar
Kendler, K. S., MacLean, C. J., Neale, M. C., Kessler, R. C., Heath, A. C. & Eaves, L. J. (1991). The genetic epidemiology of bulimia nervosa. American Journal of Psychiatry 148, 1627–1637.Google ScholarPubMed
Kendler, K. S., Neale, M. C., Kessler, R. C., Heath, A. C. & Eaves, L. J. (1992 a). A population-based twin study of major depression in women: the impact of varying definitions of illness. Archives of General Psychiatry 49, 257–266.CrossRefGoogle ScholarPubMed
Kendler, K. S., Heath, A. C., Neale, M. C., Kessler, R. C. & Eaves, L. J. (1992 b). A population-based twin study of alcoholism in women. Journal of the American Medical Association 268, 1877–1882.CrossRefGoogle ScholarPubMed
Kendler, K. S., Neale, M. C., Kessler, R. C., Heath, A. C. & Eaves, L. J. (1992 c). The genetic epidemiology of phobias in women: the inter-relationship of agoraphobia, social phobia, situational phobia and simple phobia. Archives of General Psychiatry 49, 273–281.CrossRefGoogle Scholar
Kendler. K. S., Neale, M. C., Kessler, R. C., Heath, A. C. & Eaves, L. J. (1992 d). Generalized anxiety disorder in women: a population based twin study. Archives of General Psychiatry 49, 267–272.Google Scholar
Kendler, K. S., Neale, M. C., Kessler, R. C., Heath, A. C. & Eaves, L. J. (1993 a). Panic disorder in women: a population based twin study. Psychological Medicine 23, 397–406.CrossRefGoogle ScholarPubMed
Kendler, K. S., Neale, M. C., Kessler, R. C., Heath, A. C. & Eaves, L. J. (1993 b). A test of the equal environment assumption in twin studies of psychiatric illness. Behavior Genetics 23, 21–27.CrossRefGoogle ScholarPubMed
Loehlin, J. C. & Nichols, R. C. (1976). Heredity, Environment and Personality: A Study of 850 Sets of Twins. University of Texas Press: Austin, TX.Google Scholar
Lykken, D. T., McGue, M., Bouchard, T. J. & Tellegen, A. (1990). Does contact lead to similarity or similarity to contact? Behavior Genetics 20, 547–561.CrossRefGoogle ScholarPubMed
Lytton, H. (1977). Do parents create, or respond to, differences in twins? Developmental Psychology 13, 456–459.CrossRefGoogle Scholar
Matheny, A. P. Jr. (1979). Appraisal of parental bias in twin studies: ascribed zygosity and IQ differences in twins. Acta Genetica Medica et Gemellologia 28, 155–160.Google ScholarPubMed
Morris-Yates, A., Andrews, G., Howie, P. & Henderson, S. (1990). Twins: a test of the equal environments assumption. Acta Psychiatrica Scandinavica 81, 322–326.CrossRefGoogle Scholar
Munsinger, H. & Douglass, A. II (1976). The syntactic abilities of identical twins, fraternal twins, and their siblings. Child Development 47, 40–50.CrossRefGoogle Scholar
Neale, M. C. (1991). Statistical Modelling with Mx. Department of Human Genetics, Medical College of Virginia, Virginia Commonwealth University: Richmond, VA.Google Scholar
Neale, M. C. & Cardon, L. R. (1992). Methodology for Genetic Studies of Twins and Families. Kluwer Academic Publishers B. V.: Dordrecht, The Netherlands.CrossRefGoogle Scholar
Pearson, K. (1901). Mathematical contributions to the theory of evolution. VIII. On the correlation of characters not quantitatively measurable. Proceedings of the Royal Society 66, 241–244.Google Scholar
Price, B. (1950). Primary biases in twin studies; a review of prenatal and natal difference-producing factors in monozygotic pairs. American Journal of Human Genetics 2, 293–352.Google ScholarPubMed
Robbins, L. C. (1963). The accuracy of parental recall of aspects of child development and of child rearing practices. Journal of Abnormal and Social Psychology 66, 261–270.CrossRefGoogle ScholarPubMed
Robins, L. N. & Helzer, J. E. (1985). Diagnostic Interview Schedule (DIS): Version III-A. Washington University School of Medicine: St Louis, MO.Google Scholar
Rose, R. J., Kaprio, J., Williams, C. J., Viken, R. & Obremski, K. (1990). Social contact and sibling similarity: facts, issues, and red herrings. Behavior Genetics 20, 763–778.CrossRefGoogle ScholarPubMed
Scarr, S. (1968). Environmental bias in twin studies. Eugenics Quarterly 15, 34–40.CrossRefGoogle ScholarPubMed
Scarr, S. & Carter-Saltzman, L. (1979). Twin method: defense of a critical assumption. Behavior Genetics 9, 527–542.CrossRefGoogle ScholarPubMed
Spence, J. E., Corey, L. A., Nance, W. E., Marazita, M. L., Kendler, K. S. & Schieken, R. M. (1988). Molecular analysis of twin zygosity using VNTR DNA probes. American Journal of Human Genetics 43, A159.Google Scholar
Spitzer, R. L., Williams, J. B. & Gibbon, M. (1987). Structured Clinical Interview for DSM-III-R. Biometrics Research Dept., New York State Psychiatric Institute: New York.Google Scholar
Walters, E. E., Neale, M. C., Eaves, L. J., Heath, A. C., Kessler, R. C. & Kendler, K. S. (1992). Bulimia nervosa and major depression: a study of common genetic and environmental factors. Psychological Medicine 22, 617–622.CrossRefGoogle ScholarPubMed