"All of those are markers for more severity of bipolar disorder," Saunders said.
Bipolar disorder, which affects 2.6 percent of the U.S. population, is characterized by extreme mood shifts. Symptoms can include hallucinations and delusions.
Six percent of Saunders' healthy control group had migraines, compared with 31 percent of the 412 bipolar patients. In both groups, migraines were more common in women than in men.
Men with bipolar disease who got migraines tended to have bipolar II, a variant with more severe depression and less severe mania or "high" periods.
Migraine was more common in patients who had suffered emotional or sexual abuse or emotional neglect.
The study, done with researchers from the University of Michigan, was published in the Journal of Clinical Psychiatry.
Saunders suspects that many psychiatrists do not know their patients also have migraines. The doctors may be distracted by the many other medical problems such patients tend to have. Patients may consider headaches a problem for a primary care doctor, not a psychiatrist.
She now wants to explore the possibility of a shared biological link between bipolar disorder and migraine. Valproic acid, an antiseizure medicine, is used to treat mania and prevent migraines. Abnormal inflammatory mechanisms have been found in both, and both are episodic conditions. "There is something going on in the brain that's happening only at certain times for some reason," she said.
Saunders plans to study a dietary program she hopes will affect the inflammatory response, improve mood stability, and reduce migraines. She said it would involve changing the intake of fatty acids, but wouldn't talk about the details.
Some patients, she said, have more stable moods when their migraines are well-controlled.
She said there was also a link between migraine and depression.