The authors estimate that approximately 32 million people have used LSD (lysergic acid diethylamide), psilocybin ("magic mushrooms"), or mescaline (peyote and other cacti) in their lifetime. This includes 17% of US adults aged 21 to 64 years. The highest rate of psychedelic use was in the 30 to 34 age group, with an overall rate of 20%, or 26% of males and 15% of females.
"Lifetime use of psychedelics doesn't seem to have changed much since the sixties - psychedelics continue to be widely used in the US and worldwide," the researchers say.
The mechanisms of action, subjective effects, and risk profile of the classical serotonergic psychedelics, distinguish them from other drugs, the authors wrote.
"Psychedelics are different from other drugs, in that they are not known to be physically harmful or cause addiction or compulsive use. Experts agree that psychedelics are less harmful than alcohol and most other recreational drugs, although psychedelics can elicit anxiety and confusion during the drug effects", the researchers say.
The authors estimated that older adults were more likely to have used LSD and mescaline, whereas younger adults were more likely to have used "magic mushrooms". In addition, the authors note that use of "magic mushrooms" is known to have increased since the 1970s.
"People often report mystical experiences as a major reason for using psychedelics. Archaeological evidence shows that psychedelic plants have been used in the Americas for over 5000 years, and currently around 300,000 people in the US enjoy a recognized religious freedom right to use psychedelics." Krebs and Johansen said.