Hallucinogens are illegal in the U.S., but for people who have headaches so painful they’re commonly referred to as “suicide headaches,” these drugs might be the only answer. New studies from Dr. John Halpern of McLean Hospital and Harvard Medical School reveal that the use of psychedelics such as LSD and psilocybin (found in a type of mushroom) have helped many people suffering from cluster headaches, widely accepted as the most painful kind of headache.

Dr. Halpern and his team were inspired by the Cluster Busters, a group of cluster headache sufferers determined to find a cure for their excruciating headaches who have turned to hallucinogens because they believe it’s currently the only hope. Dr. Halpern conducted a series of interviews with cluster headache sufferers and found out that these types of drugs made headache attacks less painful and/or less frequent for 41% of subjects, and ended cluster cycles altogether for 52%.

These results motivated Dr. Halpern to go even further. His team launched a small pilot study testing the effects of BOL (2-Bromo-LSD), which is almost identical to LSD, but without the psychedelic effects, on cluster headache patients. Though only a few subjects participated in the study, all of them yielded very positive results.

This early success of BOL gives sufferers hope for a legal, low-side-effect therapy for their cluster headaches. However, with so many legal issues involved, it may be years before BOL can be sold on the market as a cluster headache treatment. For the time being, this leaves many cluster headache sufferers with the unfortunate decision between toughing out these terrible headaches or turning to illegal substances.