"In 2024, 4.5% (12 million) of all adults (aged 18 years and older) in the United States reported using at least one psychedelic substance in the last 12 months (including classic psychedelic, empathogenic, and dissociative substances)."
Source
Rocky Mountain Poison & Drug Safety. (2025). Use of Psychedelic Substances in the United States, 2024: Results from the National Survey Investigating Hallucinogenic Trends (NSIHT) (RMPDS Publication No. RMPDS-2025-I-01). Rocky Mountain Poison & Drug Safety, Denver Health and Hospital Authority. Denver, CO.