Some types of psychedelic drugs, such as psilocybin and MDMA (ecstasy), have shown promise as therapies for treatment-resistant depression and post-traumatic stress disorder. They appear to work by encouraging the growth of new connections between neurons in the brain. This ability of the brain to make new connections is called plasticity.
Exactly how these drugs promote plasticity in the brain has been unclear. If the mechanisms could be understood, it might be possible to develop related drugs that can promote brain plasticity without causing unwanted hallucinogenic effects.
Previous studies have found that psychedelic drugs encourage plasticity by binding to a cellular receptor in neurons called the 5-hydroxytryptamine 2A receptor (5-HT2AR). But other compounds that bind to 5-HT2AR don’t promote plasticity. These include serotonin, a chemical messenger affected by some antidepressant treatments.
Read more at: https://www.nih.gov/news-events/nih-research-matters/how-psychedelic-drugs-may-help-depression