Comorbidity in perimenstrual migraine.

Comorbidity may be defined as the association of two or more diseases in individuals at a frequency greater than that expected statistically by chance. Studying the co-occurrence of two disorders requires a careful statistical analysis before any clear conclusion on causality is reached. Many studies have looked for an association between migraine and many diseases, reporting several sometimes controversial comorbidities in migraine subjects. Although migraine is more common in women than in men, very few studies have analyzed the comorbidity of perimenstrual migraine, a migraine sub-type characterized by attacks of migraine without aura related to menstruation. We review the studies on migraine comorbidities, particularly migraine without aura in women.