Psilocybin, a compound from certain mushrooms, is being studied as a potential rapid-acting treatment for severe depression that doesn’t respond to standard antidepressants. Unlike conventional antidepressants that take weeks to work, psilocybin shows promise for producing mood improvements within days. The drug works by activating serotonin receptors in the brain and promoting the growth of new neural connections, though researchers are still working to fully understand how it achieves its antidepressant effects.