Psychedelic therapies might benefit certain patients with mental illness, but research to date is insufficient to inform clinical practice, leading psychiatrists say.

In a clinical memorandum on the therapeutic use of psychedelic substances, the Royal Australian and New Zealand College of Psychiatrists has cautioned the evidence for their effectiveness and safety is limited.

Psychiatrist Professor David Castle, from St Vincent’s Health and the University of Melbourne, said some clinical trials had suggested the drugs were well-tolerated, but there were caveats.

“They can’t just be used by themselves — it’s part of a psychedelic-assisted psychotherapeutic approach — and the trials are mostly quite small, so they need replication,” Professor Castle said.