Psilocybin, a naturally occurring chemical in certain psychedelic mushrooms such as "Psilocybe cubensis", is being studied for its ability to help people suffering from psychological disorders, such as obsessive–compulsive disorder. Minute amounts have been reported to stop cluster and migraine headaches. A double-blind study, done by the Johns Hopkins Hospital, showed psychedelic mushrooms could provide people an experience with substantial personal meaning and spiritual significance. In the study, one third of the subjects reported ingestion of psychedelic mushrooms was the single most spiritually significant event of their lives. Over two-thirds reported it among their five most meaningful and spiritually significant events. On the other hand, one-third of the subjects reported extreme anxiety. However, the anxiety went away after a short period of time. Psilocybin mushrooms have also shown to be successful in treating addiction, specifically with alcohol and cigarettes.