Abstract
According to the Geschwind-Behan hypothesis, alterations in testosterone levels during foetal development can delay development of the left hemisphere (ie., atypical cerebral laterality). This delay is purported to increase the risk of left-handedness and disorders such as dyslexia and migraine. The same foetal influences are also thought to lead to perinatal complications (Geschwind & Behan, 1982). An empirical test of this hypothesis was undertaken with Study members enrolled in the Dunedin Multidisciplinary Health and Development Study. At age 26, headache status was determined (migraine, tension-type headache (TTH), headache-free controls) and records were examined to ascertain physical, cognitive, and neuropsychological correlates of headache. Perinatal complications did not increase the risk of headache at age 26. However, migraineurs were more likely to be left- or mixed-handed than controls. Compared to TTH sufferers and controls, migraineurs were significantly impaired on cognitive and neuropsychological tests of verbal comprehension from ages 3 to 13, but not on other tasks (e.g., verbal expression, reading, motor, memory). Nevertheless, migraineurs achieved lower School Certificate grades. Left-handed migraineurs performed marginally (though not significantly) worse on all measures. In general, the findings were consistent with the Geschwind-Behan hypothesis. They also indicate that among migraine sufferers, the association between left-handedness and learning disorder was apparent on measures of verbal comprehension (rather than reading) from an early age, suggesting poor performance was unlikely to have resulted from headache pain.