Users of barbiturates and opioids to treat migraine appear to be at an increased risk of developing a chronic form of the condition.

A study questioned 24,000 people with headaches about the medications they used to treat their symptoms.

Researchers selected people who had been diagnosed with episodic migraine in 2005 and calculated their risk of chronic migraine based on the type of drugs they used.

People who took medications containing barbiturates or opioids for eight days a month were twice as likely to develop chronic migraine a year later as those people who did not take the drugs, researchers noted.

No evidence was found to link the development of chronic migraine among frequent users of triptans to treat migraine or NSAIDs, however.

"People who use drugs that contain barbiturates and opioids, if only for a total of seven to eight days a month, appear to significantly increase their risk of migraine progression," study author Marcelo Bigal at Albert Einstein College of Medicine, New York, said.

He called for "strict limits" for barbiturates and opioids to be enforced as a means of preventing existing migraines from becoming more frequent and more painful.

Findings were presented at the American Academy of Neurology 60th Anniversary annual meeting in Chicago.

Click here to learn more about migraine

• Migraine suffers could have reduced breast cancer risk, study shows 06/11/08
• Oxygen therapies 'effective' in offering migraine relief 17/07/08
• New device proves effective in eliminating migraine 26/06/08
• Left-handedness not associated with migraine, experts show 30/05/08
• Sumatriptan, naproxen combination offers 'significant' headache relief 22/04/08