Friday, June 10, 2011

Cannabis and Psychosis (Young People) - House of Commons debates, 9 June 2011, 6:00 pm

Charles Walker MP may (as he says himself) not be an expert clinician or scientist, but he has done a rather expert job of making cannabis psychosis appear to be fact, when the evidence to support a causal link between cannabis use and psychosis, even as a contributory cause, remains entirely equivocal and open to interpretation.

Just last month, Glyn Lewis Professor of Psychiatric Epidemiology at the University of Bristol, one of the world's leading experts on the subject, said "...there is no certainty of a causal relationship between cannabis use and psychosis".

The "six times higher" figure Mr. Walker uses does his case no favours, and such abuse of science and statistics has been summarily dealt with by Ben Goldacre in his Bad Science series. I refer you to "Cherry picking data to prove a point about cannabis" in The Guardian, Saturday 24 March 2007 and to his other piece "Blah blah cannabis blah blah blah" in The Guardian Saturday, July 28 2007.

Ironically, there are accurate figures available that do show a very real increase in cannabis potency in the UK from around 1995 - 2005, when the strength of typical UK cannabis roughly doubled.

"Potency of D9-THC and Other Cannabinoids in Cannabis in England in 2005: Implications for Psychoactivity and Pharmacology" by Potter, Clark and Brown shows that from 1995 to 2005 typical cannabis potency roughly doubled to just over 13%THC.

On the basis of this, Potter et al speculated that there may be worrying implications, a possible psychosis epidemic may be on the cards due to the rise of the new "skunk" cannabis.

Fortunately the period of 1996 - 2005 was also covered in a study commissioned by the ACMD: "Assessing the impact of cannabis use on trends in diagnosed schizophrenia in the United Kingdom from 1996 to 2005" by the Department of Medicines Management, Keele University.

The study found looked at the General Practice Research Database (GPRD) "for 183 practices in England, Wales, Scotland and Northern Ireland. The study cohort comprised almost 600,000 patients each year, representing approximately 2.3% of the UK population aged 16 to 44."

The study concluded that:

"Between 1996 and 2005 the incidence and prevalence of schizophrenia and psychoses were either stable or declining... ...this study did not find any evidence of increasing schizophrenia or psychoses in the general population from 1996 to 2005."

In the same decade that cannabis strength doubled, psychosis levels either stabilised or declined.

But we could be charitable, we could allow Mr. Walker the possibility that cannabis may cause psychosis. Does this constitute a sound reason for continuing with current prohibitionist policy - under which cannabis potency has doubled in ten years? Alcohol prohibition in the USA saw the rise of distilled alcohol, and cannabis prohibition in the UK has seen the rise of double potency skunk cannabis.

The UN's own figures show that the cannabis use grew by 8.5% worldwide from 1998 - 2008.

Prohibition is not a rational drug control policy. If anything, prohibition appears to be "pro drugs" and "pro cannabis", stimulating cannabis potency and stimulating drug use.

Prohibition doesn't result in the ever-decreasing market in cannabis that its advocates think and claim it does. In fact, it does the opposite. Crop eradication programmes in Afghanistan and South America saw world opium use rise by 35% and cocaine use by 27% over the same ten year period up to 2008, according to the UN.

The consequences of cannabis prohibition, indirect and direct, are tragic - mass incarceration and tens of thousands dead each year.

60% of the Mexican cartels' income comes from cannabis. 34, 612 deaths occurred in the Mexican drug wars in the four years up to Jan 2011, mostly murders in gang competition over supply routes to the US. There are around 350,000 people in prison in the US for breaking drugs laws. Another 10,000 or more US citizens are estimated by the eminent economist Milton Friedman to die each year due to prohibition.

It's time to stop painting this discussion as People Who Like Drugs vs. People Who Don't Like Drugs.

Prohibition's days are numbered because prohibition has been shown unequivocally to be a failure. Enough of the panic-mongering and hysteria, we need a rational and compassionate drug policy.

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