Won't somebody think of the... evidence?

It took me a while to work out what was weird with Horizon's Cannabis: The Evil Weed. No bias? No clear cut agenda slowly outlined through careful editing and selection of interview subjects. This is a documentary, isn't it? And one on drugs at that.

Given the subject it was amazing just how evenly handed and open minded it was. It started with the evolution of the plant and how it's psychoactive defence mechanism evolved as protection against predators. I'm not sure how giving browsing animals the munchies is a win for plantkind but it obviously worked somehow. It even went into the biological origins of the human neurotransmitters that it interferes with to give you the giggles. Ten minutes in and not a single child threatened. The presenter Dr John Marsden did slap a young-looking cow at one point but it didn't seem bothered. The miles of wild weed behind it probably played a part there.

The real interesting stuff, however, happened when the show entered the labs to look at biochemical effects. The first claim was that it increased the tolerance of mice to harder drugs. Mice were given a button that dosed them with heroine and the ones which had previously been given cannabis pressed it more than clean mice. A lot more. The surprise was that when the effort required to get the hit was increased (by upping the number of times the button needed to be activated) everything equaled out. The druggie and normal mice both gave up at the same time. Results that suggest cannabis might increase tolerance to harder drugs but has little effect on the chance of getting hooked.

This impartial presentation of facts continued even when a family blamed cannabis for there smoker son's schizophrenia; citing the absence of mental health problems anywhere else in the family as proof that cannabis did it. Obviously. Experiments revealed it messed up mice's memories - a symptom and indicator of mental health effects - but only when administered to juveniles. They also showed brain scans of people showing how cannabis shut down frontal sections of the brain. These areas affect how we perceive the world around us, and interfering with them can cause paranoia and schizophrenia. The overall conclusion was that high use at a young age could cause problems later. As an adult: no problem.

But while it looked like a cry of "save the children!” was imminent the only comment passed was that it “shows the effects cannabis might have on the human brain.” An amazingly even handed response considering the case studies: an addict, the schizophrenic and the stoner. Predictably it was the latter who was most damning. A mugging halfwit who seemed to think saying weed was “better than sex” was one of the cleverest things ever. The stoned American businessman wasn't much better. He'd been prescribed medicinal cannabis in California for... wait for it... anxiety. He said it helped him relax which I'm pretty sure is what most people consider the point. It certainly didn't show off the medicinal benefits in the best light. Watching him drawl, resonantly and absentmindedly like a 50 year old surfer was far more off-putting than the teen talking about the voices that told him to kill himself. At least he was fun, albiet a bit stabby looking.

The most interesting thing Dr Marsden talked about was the balance of THC and CBD, the two active ingredients. THC is the one that gets you high and makes you paranoid while CDB doesn't. It's actually an antischizophrenic drug, potentially balancing out bad effects and making everything alright. Trouble it's THC that current strains have been been breed to enhance. Hence the problems. Overall, the closing statement made it clear - medically there's loads of potential but that's still no excuse for being smashed in a bed sit and discussing lyrics for the whole of your twenties.