A number of small studies have found psychedelics to show promise in treating mental health disorders like depression, addiction and post-traumatic stress disorder, often where other treatments have failed.

Now UK researchers are about to take part in the first major trials into whether one of these hallucinogenic drugs could be more effective than a leading antidepressant in the treatment of depression.

Researchers at Imperial College London are to compare the magic mushroom compound psilocybin with a leading SSRI (selective serotonin reuptake inhibitors) antidepressant, escitalopram, in a large trial expected to take at least two years.

"[Psychedelics] have a revolutionary potential, and that's not an exaggeration," says Dr Robin Carhart-Harris, who will lead the study.