It's been coming. The news that cannabis is more dangerous than tobacco, reported by the British Lung Foundation yesterday, should not really have come as a surprise to anyone. That it has shocked quite a lot of people is just another example of how the drug policy in this country doesn't add up.
According to the research, smoking three "reefers" a day does as much damage to the lungs as a whole fat pack of 20 cigarettes. This is because, on average, joint smokers mix tobacco with weed, smoke it without a filter, and inhale more deeply and for longer than cigarette smokers. Next thing you know they will be telling us that smoking drugs with disorientating properties eventually turns you a bit silly.
Such common-sense conclusions could have been drawn by anybody who has spent time with a smoker or who has smoked themselves. The fruity cough that follows a big night, the paranoia that turns every other conversation into a whispered exchange - the downsides to frequent marijuana use are pretty obvious.
Yet hash is such a political hot-rock that such plain facts are unknown to most of the estimated 2.5m Britons who smoke cannabis. For decades, politicians insisted that cannabis was an evil and a gateway to harder substances. The consequences of such a proscriptive attitude were inevitable: knowing that cannabis wasn't as bad as all that, opinion veered off in the opposite direction of the government's. Today, almost three-quarters of children are said to believe that cannabis is "safe". Add to that the list of big-time tokers who are student poster material, from Dylan to Marley to (Ali) G, and it's easy to understand why basic questions of health surrounding the drug go unasked and unanswered.
Yesterday's report, released ahead of the expected reclassification of cannabis in parliament, may not blow the lid off a generation of preconceptions. After all, it is easy to quibble with a report that says three joints equals 20 fags. "What is the standard size for a joint?" people with a fresh eighth will ask. Would 3ft-long Camberwell carrots get around the problem on a technicality?
But frequent use of marijuana has obvious problems, and not just in the long term. The woolly memory that lingers, ending conversations with "you know who I mean"; the sheer torpor that virtually chains a generation to their settees. Yet, thanks to decades of disinformation, propaganda and, yes, popular music, the truth about cannabis remains fogged in smoke.