MIGRAINE AND CONCOMITANT SYMPTOMS AMONG 8167 ADULT TWIN-PAIRS

We studied the inheritance of migraine and concomitant symptoms among 2690 monozygotic (1524 female and 1166 male) pairs and 5497 dizygotic (2951 female and 2546 male) twin pairs. Our material consists of a pop ulation-based questionnaire study among Finnish twins in 1981. The def inition of migraine is based on a questionnaire method. Concordance wa s assessed using probandwise concordance rates and tetrachoric correla tions for monozygotic (MZ) and dizygotic (DZ) twin pairs. For estimati ng the contribution of genetic factors to the susceptibility of migrai ne, a polygenic multifactorial model was used. Structural equation mod els were applied for estimating variance components and to com pare di fferent genetic models. Nearly one-half (40% to 50%) of the liability to migraine is attributable to genetic factors. In all structural anal yses, the model with both additive genetic and unshared environmental component had the best goodness-of-fit value. The genetic component va ried between 34% to 51% in different migraine types. There were no rem arkable differences between sexes except in the effects due to dominan ce, where the proportion was 26% for men and 14% for women. Concomitan t symptoms among subjects within pairs concordant for headache had gen etic effects varying from 56% (subjects with unilaterality) and 56% (s ubjects with visual symptoms) to 45% (persons with nausea and vomiting ). The two threshold model of headache points to the continuum model o f headache, and the thresholds represent different levels of severity of the pain. Our results emphasize a multifactorial and higher than pr eviously reported genetic pattern in the etiology of migraine. Also un shared environmental factors play an important role.