The inheritance of migraine with aura estimated by means of structural equation modelling

Studies of migraine with aura (RIA) have shown familial aggregation of the disorder, which cannot be explained by simple mendelian inheritance. The in terest in a genetic basis for the disorder has increased after identificati on of three genetic loci for familial hemiplegic migraine (FHM), which is a rare subtype of MA with autosomal dominant inheritance. Both genetic and e nvironmental factors seem to be important in the expression of MA. To eluci date the molecular pathogenesis of MA, knowledge of the relative role of ge netic and environmental factors is essential. Twin studies are a classic wa y to analyse this. We applied structural equation modelling on MA with twin data obtained from a population based twin register in order to evaluate t he effects of genes and environment. The correlation in liability of MA was 0.68 in monozygotic (MZ) and 0.22 in dizygotic (DZ) twin pairs, indicating a high degree of genetic determination in the total variance of liability. The best fitting model combined additive genetic effects and environmental effects that were not shared by the twins. The estimate of heritability wa s 0.65 and similar in males and females.