The topic was covered well by Monte and Adam also.
Anyway, this caught my eye:
Abuse in childhood linked to migraine and other pain disorders
Researchers from the American Headache Society's Women's Issues Section Research Consortium found that incidence of childhood maltreatment, especially emotional abuse and neglect, are prevalent in migraine patients. The study also found that migraineurs reporting childhood emotional or physical abuse and/or neglect had a significantly higher number of comorbid pain conditions compared with those without a history of maltreatment. Full findings of the study appear in the January issue of Headache: The Journal of Head and Face Pain,