Clouded in controversy

FOR much of the past 20 years a broad consensus prevailed that cannabis was the least harmful of street drugs and that its downgrading to Class C would, inter alia, enable the police to concentrate their efforts on the trade in heroin and crack cocaine.

But since Tony Blair's downgrading in 2004 there has been growing controversy over quite how "harmless" the cannabis drug really is, and the dangers it can pose to mental health. The review by the Advisory Council on the Misuse of Drugs – commissione...