What is the clinical evidence on psilocybin for the treatment of psychiatric disorders? A systematic review

BACKGROUND: Psilocybin is a predominant agonist of 5HT(1A) and 5HT(2A/C) receptors and was first isolated in 1958, shortly before it became a controlled substance. Research on the potential therapeutic effects of this compound has recently re-emerged alongside what is being addressed as a psychedelic renaissance. METHODS: In this paper we performed a systematic review of the clinical trials conducted so far regarding the therapeutic effects of psilocybin on psychiatric disorders. The eligibility criteria included clinical trials that assessed psilocybin's potential therapeutic effects on patients with psychiatric disorders. Nine hundred seven articles were found and screened in regard to the title, from which 94 were screened through abstract and 9 met the eligibility criteria and were included. RESULTS: The papers published focused on 3 disorders: depression, obsessive-compulsive disorder (OCD) and substance use disorder (namely tobacco and alcohol). Psilocybin has shown a relatively safe profile and very promising results, with reductions found on most of the psychiatric rating scales’ scores. Research on depression showed the most solid evidence, supported by 3 randomized controlled trials. Studies on OCD and substance use disorder showed more limitations due to their open-label design. CONCLUSIONS: Altogether, the results from the studies reviewed in this paper suggest a substantial therapeutic potential. This calls for further research to confirm the results observed so far and further explain the underlying mechanisms.