Initial interest in the value of psychedelic drugs (“psychotomimetics”) in psychiatry began in the early 20th century, with explorations of the possibility that mescaline or peyote could produce psychosis-like effects. Over time, interest was focused on whether the effects of psychedelics could inform as to the underlying basis for psychiatric disorders. As research continued, and especially after the discovery of LSD in 1943, increasing interest in a role for psychedelics as adjuncts to psychotherapy began to evolve and became the major focus of work with psychedelics up to the present day.
Nichols, D. E., & Walter, H. (2021). The History of Psychedelics in Psychiatry. Pharmacopsychiatry, 54(4), 151–166. https://doi.org/10.1055/a-1310-3990