Figure 4.

Genetic and environmental factors and migraine predisposition. Migraine conditions are primarily considered polygenic complex disorders of which genetic (inherited) and environmental risk factors, as well as interactions, constitute headache predisposition. (a) The bar plot illustrates a proposed hypothesis of individual migraine development. The migraine threshold, termed cutoff, shows the point at which subjects are diagnosed with migraine (ratio ≥ 1). Subject A is a non-migraineur and subject B-D migraineurs. (b) Subject B has developed migraine due to an equal predisposition from genetic (50%) and environmental factors (50%), subject C mainly due to environmental predisposition (92%) and subject D mainly due to genetic predisposition (75%).