Abstract
The equal-environments assumption (EEA) in twin studies of psychiatric disorders assumes that the family environment which contributes to risk for a disorder is equally correlated between monozygotic (MZ) and dizygotic (DZ) twin pairs. In a study of psychiatric disorders in female twins, Kendler and colleagues (1993) have demonstrated the utility of a test of the EEA which includes a specified family environmental factor defined by using measures of perceived zygosity. We tested the EEA assumption among 3155 male—male twin pair members of the Vietnam Era Twin Registry for the following DSM-III-R lifetime disorders: alcohol dependence, marijuana dependence, any illicit drug dependence, nicotine dependence, major depression, and posttraumatic stress disorder. The majority of MZ (81.6%; n = 1593) and DZ (90.2%; n = 1086) twin pairs agreed with the investigator's assigned zygosity. The best-fitting model for each of these disorders did not allow for a specified family environmental influence. These results support the usefulness of perceived zygosity in tests of the EEA. In male twin pairs, perceived zygosity has little impact on twin similarity for common psychiatric disorders.
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REFERENCES
Akaike, H. (1987). Factor analysis and AIC. Psychometrics 52: 317–333.
American Psychiatric Association (1987). Diagnostic and Statistical Manual of Mental Disorders, 3rd ed., rev., American Psychiatric Association, Washington, DC.
Eisen, S. A., True, W. R., Goldberg, J., Henderson, W., and Robinette, C. D. (1987). The Vietnam Era Twin (VET) Registry: method of construction. Acta Genet. Med. Gemellol. (Roma) 36:61–66.
Eisen, S. A., Neuman, R., Goldberg, J., Rice, J., and True, W. (1989). Determining zygosity in the Vietnam Era Twin Registry: An approach using questionnaires. Clin. Genet. 35:423–432.
Henderson, W. G., Eisen, S., Goldberg, J., True, W. R., Barnes, J. E., and Vitek, M. E. (1990). The Vietnam Era Twin Registry: a resource for medical research. Public Health Rep. 105:368–373.
Kendler, K. S., Neale, M. C., Kessler, R. C., Heath, A. C., and Eaves, L. J. (1993). A test of the equal-environment assumption in twin studies of psychiatric illness. Behav. Genet. 23:21–27.
Loehlin, J. C., and Nichols, R. C. (1976). Heredity, Environment and Personality: a Study of 850 Sets of Twins, University of Texas Press, Austin.
Lyons, M. J., True, W. R., Eisen, S. A., Goldberg, J., Meyer, J. M., Faraone, S. V., Eaves, L. J., and Tsuang, M. T. (1995). Differential heritability of adult and juvenile antisocial traits. Arch. Gen. Psychiatry 52:906–915.
Lyons M. J., Eisen, S. A., Goldberg, J., True, W., Lin, N., Meyer, J. M., Toomey, R., Faraone, S. V., Merla-Ramos, M., and Tsuang, M. T. (1998). A registry-based twin study of depression in men. Arch. Gen. Psychiatry 55:468–472.
Lytton, H. (1977). Do parents create, or respond to differences in twins? Dev. Psychol. 13:456–459.
Magnus, P., Berg, K., and Nance, W. E. (1983). Predicting zygosity in Norwegian twin pairs born 1915–1960. Clin. Genet. 24:103–112.
Matheny, A. P., Jr. (1979). Appraisal of parental bias in twin studies. Ascribed zygosity and IQ differences in twins. Acta Genet. Med. Gemellol. (Roma) 28:155–160.
Matheny, A. P., Jr., Wilson, R. S., and Dolan, A. B. (1976). Relations between twins' similarity of appearance and behavioral similarity: Testing an assumption. Behav. Genet. 6:343–351.
Neale, M. C. (1999). Mx: Statistical Modeling, 5th ed., Box 126, MCV, Richmond, VA 23298.
Robins, L., Helzer, J., Cottler, L., and Goldring, E. (1988). NIMH Diagnostic Interview Schedule Version III Revised (DIS-III-R), Department of Psychiatry, Washington University Medical School, St. Louis, MO.
Scarr, S. (1968). Environmental bias in twin studies. Eugen. Q. 15: 34–40.
Scarr, S., and C W. S., True, W. R., Scherrer, J. F., Heath, A. C., Bucholz, K. K., Eisen, S. A., Goldberg, J., Lyons, M. J., and Tsuang, M. T. (1999). The heritability of alcoholism symptoms: “Indicators of genetic and environmental influence in alcohol-dependent individuals” revisited. Alcohol. Clin. Exp. Res. 23: 759–769.
Spitz, E., Moutier, R., Reed, T., Busnel, M. C., Marchaland, C., Roubertoux, P. L., and Carlier, M. (1996). Comparative diagnoses of twin zygosity by SSLP variant analysis, questionnaire, and dermatoglyphic analysis. Behav. Genet. 26:55–63
True, W. R., Xian, H., Scherrer, J. F., Madden, P. A. F., Bucholz, K. K., Heath, A. C., Eisen, S. A., Lyons, M. J., Goldberg, J., and Tsuang, M. (1999a). Common genetic vulnerability for nicotine and alcohol dependence in men. Arch. Gen. Psychiatry 56:655–661.
True, W. R., Heath, A. C., Scherrer, J. F., Xian, H., Lin, N., Eisen, S. A., Lyons, M. J., Goldberg, J., and Tsuang, M. T. (1999b). Interrelationship of genetic and environmental influences on conduct disorder and alcohol and marijuana dependence symptoms. Am. J. Med. Genet. (Neuropsychiatr. Genet.) 88:391–397.
Tsuang, M. T., Lyons, M. J., Eisen, S. A., Goldberg, J., True, W., Lin, N., Meyer J. M., Toomey, R., Faraone, S. V., and Eaves, L. (1996). Genetic influences on DSM-III-R drug abuse and dependence: A study of 3,372 twin pairs. Am. J. Med. Genet. (Neuropsychiatr. Genet.) 67:473–477.
Xian, H., Chantarujikapong, S. I., Scherrer, J. F., Eisen, S. A., Lyons, M. J., Goldberg, J., Tsuang, M., and True, W. R. (2000). Genetic and environmental influences on posttraumatic stress disorder, alcohol and drug dependence in twin pairs. Drug. Alcohol Depend. (in press).
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Xian, H., Scherrer, J.F., Eisen, S.A. et al. Self-Reported Zygosity and the Equal-Environments Assumption for Psychiatric Disorders in the Vietnam Era Twin Registry. Behav Genet 30, 303–310 (2000). https://doi.org/10.1023/A:1026549417364
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DOI: https://doi.org/10.1023/A:1026549417364