Answer:
As of my knowledge cutoff in September 2021, the only hallucinogen that has been approved by the U.S. Food and Drug Administration (FDA) as a treatment for depression is Esketamine. Esketamine is a derivative of ketamine, a dissociative anesthetic commonly used in medical and veterinary settings. The FDA approved Esketamine nasal spray, under the brand name Spravato, for use in conjunction with an oral antidepressant for adults with treatment-resistant depression. However, please note that the field of medicine is constantly evolving, and there may have been updates or new approvals since my knowledge cutoff date. It is always best to consult the latest information and sources for the most up-to-date and accurate information regarding FDA approvals and treatments for depression.