As a psychiatrist and drug addiction specialist, Associate Prof Dr Rusdi Abd Rashid has seen the adverse effects of marijuana on patients and how it can induce psychosis in those with schizophrenia and other mental disorders.

So he was surprised to see how it calmed down the severely autistic son of a patient who had been depressed because she was unable to cope with her son’s condition.

“She (had given) the CBD (cannabidiol) oil to her son – she just put a few drops under...