Two new studies into psilocybin - the ingredient in magic mushrooms that makes them so popular - have raised hopes it could soon become a mainstream medicine used to treat depression and anxiety.
Psilocybin's therapeutic potential has been studied as far back as the 1960s, but only recently have scientists begun to uncover just how effective it might be. Research published last year found a single dose could relieve anxiety and depression in cancer patients, for example - a much less onerous regime than taking a course of pills.
The first of the new studies out this week compared psilocybin to escitalopram, a selective serotonin reuptake inhibitor also known by the brand names Loxalate and Lexapro.
After six weeks of treatment - which is about how long it takes for the benefits of escitalopram to kick in - both people on the antidepressant drug and psilocybin showed clinical improvements. The group on psilocybin actually performed slightly better, but the lead over escitalopram wasn't significant, researchers at Imperial College London said in their paper, published in the New England Journal of Medicine.
There were no serious adverse events in either group.
Long-term trials of psilocybin however are rare, with participants having to stay under close watch in case of hallucinations. But a second study out of the US has found the antidepressant benefits of psilocybin might have nothing to do with the hallucinogenic effects.
"We do not understand the mechanisms that underlie the antidepressant actions of psilocybin and the role that the profound psychedelic experience during these sessions plays in the therapeutic benefits," said Scott Thompson of the University of Maryland School of Medicine.
"The psychedelic experience is incredibly powerful and can be life-changing, but that could be too much for some people or not appropriate."
It can also, in rare cases, lead to psychosis - particularly in people with mental health issues, the very kind doctors want to help with psilocybin.
Dr Thompson's team stressed out a group of mice for two to three weeks, until they showed signs of depression - such as losing pleasure from "rewarding events". A single dose of psilocybin had them acting largely normal again 24 hours later.
So they tried it again, this time giving the mice not just psilocybin but also ketanserin. Ketanserin blocks psilocybin from accessing the serotonin 2A receptor in the mice's brain, stopping it from having any psychedelic effects.
The effects on their mood were identical to psilocybin alone.
"These findings show that activation of the receptor causing the psychedelic effect isn't absolutely required for the antidepressant benefits, at least in mice," said Dr Thompson, "but the same experiment needs to be performed in depressed human subjects."
The research was published in journal Proceedings of the National Academy of Sciences on Tuesday.
