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Although it has long been recognized that there is increased risk of divorce among the children of divorced parents, the extent to which genetic and environmental factors contribute to this familial resemblance has been a matter of speculation only. In order to resolve the separate influence of genetic and environmental factors on risk of divorce, divorce status of 1,516 same-sex twin pairs (722 monozygotic. MZ, and 794 dizygotic. DZ), their parents, and their spouses' parents was determined. Concordance for divorce was significantly higher in MZ than DZ twins; this was true overall, in both the male and female samples, for both younger and older twin pairs, and both when the twins' parents had been divorced and when they had not been divorced. The robustness and magnitude of the MZ-DZ difference in divorce concordance indicates a strong influence of genetic factors in the etiology of divorce. Moreover, family background of both spouses contributed independently to couples' divorce risk, suggesting that, in many cases, divorce may be largely the result of characteristics the two spouses bring to the union rather than to interaction effects. These results also suggest that the adjustment difficulties seen with some children of divorced parents may be due to an interaction between genetic and environmental factors rather than environmental influences alone, as is assumed in many theories of divorce's effects.
McGue et al. (Sun,) studied this question.