Hallucinogens powerfully affect the brain, distorting the way our five senses work and changing our impressions of time and space. People who use these drugs a lot may have a hard time concentrating, communicating, or telling the difference between reality and illusion.
Your brain controls all of your perceptions -- the way you see, hear, smell, taste, and feel. How does your brain communicate with the rest of your body? Chemical messengers transmit information from nerve cell to nerve cell in the body and the brain. Messages are constantly being sent back and forth with amazing speed.
Your nerve cells are called neurons, and their chemical messengers are called neurotransmitters. When neurotransmitters attach to special places on nerve cells (called receptors), they cause changes in the nerve cells.
This communication system can be disrupted by chemicals like hallucinogens, and the results are changes in the way you sense the world around you.
Psilocin, the active metabolite of psilocybin, acts by interaction with neurotransmitter receptors on nerve cells in the brain where it mimicks the action of serotonin (5-HT). Specifically, psilocin is a post-synaptic 5-HT2A receptor agonist. This is the same mechanism of action as for the other hallucinogens like LSD, mescaline, or 2C-B. LSD and psilocybin show cross-tolerance — after taking one of these substances, the brain quickly develops a tolerance to it, and taking another dose of either soon afterward will require more than usual to achieve the desired effects.
Psilocybin has been studied as a treatment for several disorders.
In the US, an FDA-approved study supported by MAPS (Multidisciplinary Association for Psychedelic Studies) began in 2001 to study the effects of psilocybin on patients with obsessive-compulsive disorder. MAPS has also proposed studying psilocybin's potential application for the treatment of cluster headaches based on anecdotal evidence presented to them by a cluster headache sufferer.