Six patients suffering from cluster headaches were successfully treated with 2-bromo-LSD, a nonhallucinogenic analog of LSD, according to a pilot study presented at the International Headache Congress.

Cluster headaches are a neurological condition that cause extremely painful headaches, similar to a severe migraine, and affects about 0.1 percent of the population. Due to the intensity of the pain caused by cluster headaches, many doctors consider it one of the most painful conditions in existence and they have earned the name "suicide headaches."

ScienceNOW reported that the patients treated with 2-bromo-LSD showed a significant reduction in cluster headaches, with some being free of the attacks for weeks or months.

"Some of these patients are still reporting significant relief more than a year after they were treated with the compound," John Halpern, a psychiatrist at Harvard Medical School in Boston and an author of the study, said. "Nobody has ever reported these kinds of results."

The patients were administered 2-bromo-LSD once every 5 days for a total of three times. They all reported a reduction in frequency of cluster headaches, and five of the six patients reporting having no symptoms for over a month.

"There seems to be a long-term prophylactic effect that we cannot explain," Halpern said. "Compared to what these headache sufferers currently have available to them, this is quite remarkable. It could lead to a near-cure-like treatment."

Although the results are promising, the study's findings are severely limited by its small sample size and lack of a control group, making it impossible to rule out a placebo effect.

Hallucinogenic drugs like LSD have been rumored to stop cluster headaches, but because of its illegal status, few studies have investigated the matter.

The scientific journal Neurology published a report by Halpern and his colleagues in 2006 that investigated the use of LSD and another hallucinogen, psilocybin, for the treatment of cluster headaches.

The authors of the report interviewed 53 people that had suffered from cluster headaches and used either psilocybin or LSD to treat their condition. The participants in this study were found by using an online survey.

Although hundreds of people responded to the survey, the authors excluded those whose medical records could either not be obtained or did not reliably support a diagnosis of cluster headaches.

Psilocybin and LSD were both reported to have an effect on cluster headaches. As the authors note, “Twenty-two of 26 psilocybin users reported that psilocybin aborted attacks; 25 of 48 psilocybin users and 7 of 8 LSD users reported cluster period termination; 18 of 19 psilocybin users and 4 of 5 LSD users reported remission period extension.”