Migraine has no single cause. It can be seen as a reaction of the organism, probably determined by the hypothalamus and released by a variety of extrinsic and intrinsic factors. Several factors may determine attacks at different times within a patient's lifetime. Vascular reactions are secondary to the primary cerebral mechanism, and account for many of the symptoms, notably the headache. The prodrome, aura, and the incubation during sleep are part of the attack.

Emotional disturbance is the commonest single trigger mechanism, and is the most important cause of frequent and severe attacks. There is, however, nothing specific about the emotional stimulus, nor is there a consistent personality type in migraine subjects. Certain personality reactions and patterns of behavior recur in migraine subjects; a tendency to anxiety reactions, sensitivity to stress and difficulty in handling aggressive and hostile drives. In this respect, migraine is similar to many other “psychosomatic diseases” without demonstrable pathology but characterized by disorders of homeostasis. In some patients extrinsic physical and biochemical precipitants are prominent and the “psychosomatic element” is slight. In most migraine patients, however, psychologic factors are important but are secondary rather than precipitating etiologic agents.