As many as 5.5 million Americans lack access to adequate treatment for severe migraines, Harvard Medical School researchers say.

The findings, published yesterday in the journal Neurology, indicate that uninsured patients were nearly twice as likely as the privately insured to receive substandard treatment for migraines.

Medicaid enrollees were 50 percent more likely to get substandard care, and the researchers suggest that access to some forms of insurance does not necessarily translate into adequate care.

The researchers analyzed 6,814 visits for migraines between 1997 and 2007—a nationally representative sample of the 68.6 million visits to doctors’ offices, hospital clinics, and emergency rooms.

Roughly 12 percent of Americans suffer from migraines, and about 45.7 million are currently uninsured, leaving a substantial portion of the country vulnerable to substandard migraine treatment.

Although Congress last month passed healthcare reform legislation intended to extend coverage to more Americans, a substantial population will remain vulnerable, according to Medical School neurology professor Rachel Nardin, who is senior author of the study. “Unfortunately, the new health law doesn’t fully address this problem.”

University Health Services director David S. Rosenthal ’59 noted that Massachusetts law requires that students living in the state hold health insurance policies, meaning that all students currently at the College can expect to have access to adequate care.