Reefer madness: an interlude.

Shock, horror, disaster! Call the riot boys, summon the G8! Get your placards out! Cannabis causes brain damage!

Well, sort of. Ish. We think. But it's been days since the last teen stabbing and it's a slow news morning, so let's have a moral panic anyway. Cue headlines splashed with the latest drug trials that prove next to nothing about the effects of marijuana on the human brain, as if that were the point.

Let's take an example: alcohol is our nation's biggest drug problem. Now, in tests that have been carried out so far, medium-to-low-level use of cannabis - a few joints a week for a few years, say - has been shown to display no correlation with changes in brain composition and chemistry. Likewise, there has been little evidence to show that a few units of alcohol a week does any permanent damage to one's system.

But the most recent studies on THC, the active ingredient in cannabis, examine people who've been smoking five or more joints per day for upwards of ten years. That, my dears, is one significant fucking habit. It's the equivalent of major, long-term alcoholism. And both addictions, taken to extreme, cause brain damage along with a host of other symptoms. If you're at an equivalent stage of advanced alcoholism, your memory will be dodgy, your sleep patterns shot to hell and your stress levels all over the place, not to mention the fact that you've probably fried your liver and kidneys. Likewise, if you've been smoking five joints a day for ten years all by yourself, you may well have a slightly shrunken amygdala, but your biggest and most immediate problem is probably going to be lung damage.

So let's compare this to another damaging behavior: self-harm. If you carried out equivalent studies on groups of self harmers with a control group, one would probably find that the self-harmers as a whole displayed significantly higher levels of depression and medium- to high-level manic and schizophrenic symptoms than the non-self-harming teenagers. Does this mean that self-harm causes brain damage? Of course not.

Alcohol, self-harm, hard drug use, smoking, unsafe sex, smoking cannabis. All of these activities have been shown to be more prevalent amongst the depressed and emotionally disordered, and particularly amongst the depressed and emotionally disordered young. But they are aggravating symptoms, not the cause of the problem. It's only logical that chemical escapism, offered by these drugs and addictions in their extremes, is a resort likely to be most tempting to those who have most to escape from.

Which is not to say that it's a good idea to spend all of your time stoned. It's a very BAD idea to spend all of your time stoned, especially if you care at all about your lung capacity. But it's no worse for you than, say, mild alcoholism, and there's no reason for it to be criminalised when alcohol isn't. The effect of the continued criminalisation - and, now, of reclassification despite leading doctors' advice - of cannabis is simply to make users more financially and emotionally dependent on illegal drug-dealers, and less likely to seek help when , like young alcoholics, they recognise that their problems have superseded their control.

The trouble with the THC debate is that it tends to be polarised between subjective extremes. On the one hand, there are the hard-liners like Gordon Brown who just hate hippies, stoners and all their ilk; then there are parents understandably blinkered by fear for their children, and conservatives eager to jump on the latest bandwagon condemning the coping mechanisms of any social underclass. (Janine has a brilliant piece today commenting on the continued legality of alcohol at the Henley Regatta).

On the other hand, there are the producers of High Times and their mates, the great semi-washed, stoning masses who may or may not be otherwise useful members of society. Addicts frantic to defend their habit. Endless arguments over late-night spliffs that usually begin with a lazy generalised attack on NewLabour and end when someone starts quoting Bill Hicks. This isn't the whole story either.

The simple fact is that this country has a problem with drugs and drink: period. For Joe average dope fiend and Jill average booze hound, low-level use doesn't often present that much of a problem, particularly if you don't have a Facebook account. But there are heavy users, serious addicts, people who peddle away their lives to the drug, and they do have problems - problems that don't need in-depth psychiatric studies to demonstrate their urgency.

As a nation, we've fostered for several generations a serious weed habit that's growing to form a plausible second option to the nation's favourite hobby: boozing. We're a nation of alcoholics; we've been a nation of alcoholics for centuries. Alcohol is the drug of imperialism. It makes you rowdy, aggressive, navel-gazing, horny and insidious, strips you of humility and moderation, gives you a self-inflated sense of your own importance, psyches you up for a fuck and a fight. Alcohol is something the British have long internalised as a part of their cultural identity. Weed isn't. No stoner that we know of ever colonised Africa; violent stoners laying out gender hierarchies by beating their wives and children is another cultural norm that's yet to be identified. Weed saps away every hypercapitalist drive to improve oneself, to fight and conquer, to produce and to consume on ever more dizzying scales. Joint-in-hand, one is quite happy to spend another evening on the sofa chatting to your mates about the semiotics of 1980s cartoons. Not so the bottle. A drunken British public is something the system has come to accept, despite periodic media panics over the moral health of the nation, usually timed to coincede with periods of relative conservatism and economic slowdown.

We need to have an open and objective national conversation about weed. Marjunana is neither a panacaea nor about to tip us into an immediate cross-generational psychotic break, but it is a national health problem, a problem that needs to be understood and addressed. Increasing criminalisation, victimising the young and the mentally distressed and frantic media scaremongering add nothing useful to the TCH debate. Honest and balanced reportage in non-judgemental conversation with users, healthcare professionals and families alike might just take us one step closer to understanding the real scale of harm that this drug causes. So let's begin it.