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Do “Skunk” Stats Stink?

British newspapers clash over drug war: is super-cannabis turning users schizo?

Britain is in the middle of a newspaper war about whether some newspapers went too far in advocating liberalization of the nation’s drug laws. On Monday, the Daily Telegraph ran a front-page headline “Skunk killed my beloved son,” wherein a mother recounted the suicide of her teenage son, after a descent into “cannabis induced psychosis.”

“I was stunned to learn that cannabis could be so harmful - it bore no resemblance to the drug I had puffed once or twice at university. And although it has been around for years, I had never heard of skunk, the superstrength variety that is now increasingly available. It bears almost no relation to the resin sold 10 years ago, containing 25 times the amount of tetrahydrocannabidinol, the main psychoactive ingredient.”

She then criticized another newspaper, the Independent on Sunday (IOS), for taking “so long” to reverse its call for the decriminalization of cannabis, which it had done in a dramatic front-page announcement the previous week:

“Record numbers of teenagers are requiring drug treatment as a result of smoking skunk, the highly potent cannabis strain that is 25 times stronger than resin sold a decade ago.

More than 22,000 people were treated last year for cannabis addiction - and almost half of those affected were under 18. With doctors and drugs experts warning that skunk can be as damaging as cocaine and heroin, leading to mental health problems and psychosis for thousands of teenagers, The Independent on Sunday has today reversed its landmark campaign for cannabis use to be decriminalised.”

The IOS also noted in the same edition, and then again the following week after it was published, a study that appeared to back up the link between psychosis and the increased cannabis consumption.

“Research published yesterday predicts that cannabis may account for a quarter of all new cases of schizophrenia in three years' time.

The study, published in the journal Addiction, also says that rates of schizophrenia will increase substantially by the end of the decade, particularly among young men. The use of cannabis among under-18s rose 18-fold in the 30 years to 2002, according to the researchers from Bristol University.”

First off, focus on the word “may.” Here’s what the press release on the journal’s website actually says about the study:

“If cannabis causes schizophrenia - and that remains the question - then by 2010 up to 25% of new cases of schizophrenia in the UK may be due to cannabis….”

“John Macleod, co-author and academic GP, says “We need to remember that our study does not address the question whether cannabis causes schizophrenia, this remains unclear.” Matthew Hickman, lead author of the study, comments, “The challenge now is to improve our data on schizophrenia occurrence, an undoubtedly important disease, to see whether the projected increase occurs – which will tell us more about how important cannabis is as a cause of schizophrenia.”

And one of the key problems in trying to determine whether pot is a trigger for schizophrenia is, as STATS Maia Szalavitz pointed out in Salon, is that experts say

“…it's very difficult to determine whether pot smoking predisposes people to schizophrenia or whether early symptoms of schizophrenia predispose people to smoking pot -- or whether some third factor causes some people to be more vulnerable to both.”

In a campaign to warn American parents about the connection between pot and schizophrenia, a study of almost 50,000 Swedish soldiers between the ages of 18 and 20 “found that those who had smoked pot more than 50 times had a rate of schizophrenia nearly seven times as high as those who did not use marijuana at all.” But as Szalavitz noted,

“…when factors already known to increase risk for schizophrenia were removed, such as a childhood history of disturbed behavior, the connection between marijuana use and risk for the disease was substantially reduced. Just one or two additional unknown influences could potentially wipe out the apparent marijuana-schizophrenia link, according to Dr. William Carpenter, a professor of psychiatry and pharmacology at the University of Maryland. Carpenter noted in a letter published in the British Journal of Psychiatry in October 2004 that the same genes that predispose someone to schizophrenia might also predispose them to substance abuse, but that drug use might start earlier simply because many people start using drugs in their teen years, while schizophrenia most commonly begins in the early 20s.”

There are also other specific factors to teenage life in Britain that need to be considered in looking at rising rates of schizophrenia. As psychologist Oliver James notes in his recent book Affluenza, studies have shown that the rate of emotional distress in girls that can require hospitalization rose from 6 to 18% from 1987 and 1999. This coincided with girls outperforming boys academically in almost every subject according to national examination statistics; a number of studies have shown a startling correlation between superior academic performance and schizophrenia.

By the same token as the warning about cannabis, Britain’s newspapers (and the American government) ought to be warning parents about letting their daughters study too hard. Or is it that incipient schizophrenia predisposes girls to higher levels of academic performance?

This is not to say that pot or cannabis with high levels of THC is harmless – chronic drug usage is often a proxy medication for emotional and mental problems, and should be seen as a warning sign rather than a symbol of being hip. But fixing the blame on pot or cannabis for condition X is just as much a misdiagnosis as using either drug is mistreatment for condition Y.

The issue of whether “skunk” is cracked up to be, well, almost as potent as crack was taken on by the Guardian’s “Bad Science” column, which is written by Dr. Ben Goldacre:

“There is exceptionally strong cannabis to be found in some parts of the UK market today: but there always has been. The UN Drug Control Programme has detailed vintage data for the UK online. In 1975 the LGC analysed 50 seized samples of herbal cannabis: 10 were from Thailand, with an average potency of 7.8%, the highest 17%. In 1975 they analysed 11 samples of seized resin, six from Morocco, average strength 9%, with a range from 4% to 16%.

To get their scare figure, the Independent compared the worst cannabis from the past with the best cannabis of today. But you could have cooked the books the same way 30 years ago: in 1975 the weakest herbal cannabis analysed was 0.2%; in 1978 the strongest was 12%. Oh my god: in just three years herbal cannabis has become 60 times stronger.”

In claiming that super-duper cannabis is as or more dangerous than drugs like heroin or ecstasy, the Independent seems to be making the argument that because a relatively harmless drug used by a large number of people will lead to greater numbers of people seeking treatment for side effects, such as schizophrenia, it is more dangerous than a more harmful drug used by fewer people but which kills. Now that’s a message about drugs that the Independent should apologize for.