Key points from article :
Microdoses of psychedelic drugs bring mental benefits may be due to the placebo effect.
They may take 10 to 20 per cent of a normal dose, a few times a week.
Used internet forums to contact people who were already frequently microdosing at home using LSD or similar drugs.
A third of the participants took only the drug microdoses for four weeks, one third got placebo capsules and another third got half and half.
Volunteers shouldn’t have been able to tell from the envelopes what they were taking.
Researchers could find out by analysing the QR codes at the end of the trial.
Volunteers answered subjective questionnaires about mood and experiences.
All three groups experienced similar improvements in long-term psychological and cognitive outcomes.
"People who took the real drugs showed incredibly small benefits," - Balázs Szigeti, lead author.
The trial may not be the final word, partly because the volunteers weren’t supervised by clinicians.
Study by Imperial College London published in eLife.