The premenstrual syndrome: a twin study.

Data are presented from 157 monozygotic and 143 dizygotic female twin pairs of reproductive age who completed a self-report questionnaire on the premenstrual syndrome (PMS). For global PMS scores, the correlation coefficient for the monozygotic twins (0.55) was double that of the dizygotic ones (0.28). The results are consistent with the hypothesis that aggregation for global PMS scores is determined by genetic factors acting additively over a number of loci. Two alternative explanations are suggested: that monozygotic twins share greater environmental similarities than dizygotic ones; or that PMS scores may be a reflection of some other underlying characteristic (such as neuroticism), which is itself genetically determined.