Two molecules could be better than one (Image: Fotex/Rex Features)

THE effects of cannabis on mental health have attracted much attention over the years. As far back as the 19th century it was recognised that cannabis could induce a transient psychosis which mimics the symptoms of schizophrenia. Despite this, until the last decade or so, most psychiatrists regarded cannabis as essentially benign.

This, however, is at odds with recent research which concludes that in a susceptible minority, cannabis use can push the brain towards long-term psychosis requiring mental health treatment. Susceptible young people who use cannabis increase their risk of …