Psilocybin, the naturally occurring ingredient in “magic mushrooms,” works on serotonin receptors of the brain to produce mind-altering psychedelic effects for several hours a sense of euphoria and spirituality, hallucinations and a distorted sense of time. But it can have adverse effects such as nausea and panic. Although it has not been legal to grow, possess or sell in Canada since 1974, this summer, Health Canada approved exemptions under the Controlled Drugs and Substances Act. Terminal patients were granted an exemption in August, followed by approval in November for Strelaeff, who was the first non-palliative patient. On Tuesday, 17 therapists, including doctors, nurses and psychiatrists, received federal approval to try the drug.