There's a reason they call it getting wasted
Researchers warn marijuana is worse than tobacco for your lungs and is linked to schizophrenia. ALAN FREEMAN reports
By ALAN FREEMAN
Saturday, November 16, 2002
Globe and Mail Print Edition, Page F7
LONDON -- Marijuana has always been seen as the laid-back drug. It might make you crave ice cream and chocolate cake or induce you to fall asleep, but it certainly wasn't dangerous.
Yet, as governments in Britain and Canada consider decriminalizing the drug, medical researchers are warning that smoking cannabis increases the risk of lung disease and, more disturbingly, that its use can exacerbate psychosis and that it is linked with the onset of schizophrenia in adolescents.
"We have the evidence of cannabis and its dangers," said Dr. Richard Russell, a respiratory specialist and a spokesman for the British Lung Foundation, which published a report this week on the dangers of cannabis.
"What we really want to avoid is the situation we had in the 1930s, '40s and '50s with cigarettes, where doctors were recommending tobacco as being good for you."
In its report, the lung foundation warns that cannabis is more harmful to the lungs than tobacco. It says smoking three joints a day can cause the same damage as 20 cigarettes, and tar from marijuana contains 50 per cent more carcinogens than that from tobacco.
Persistent users are risking lung cancer, emphysema, bronchitis and other respiratory illnesses, it says.
One of the major problems is posed by the way users smoke marijuana and hashish: They take puffs that are almost twice as large as those tobacco smokers take and hold the smoke in four times as long. "This means that there is a greater respiratory burden of carbon monoxide and smoke particulates such as tar than when smoking a similar quantity of tobacco."
The foundation also noted that in the 1960s, the average marijuana joint contained about 10 milligrams of tetrahydrocannabinol (THC), which accounts for the drug's psychoactive properties. Because of sophisticated cultivation techniques, the average joint today has 150 mg of THC, a 15-fold increase.
Dr. Russell, the respiratory specialist, worries that young people think cannabis is a "cool drug" that is risk-free. A survey carried out this year showed that 79 per cent of British children believe cannabis is safe.
The Canadian government indicated in its Speech from the Throne last month that it is considering the decriminalization of marijuana possession.
Already, it gives exemptions to drug laws to allow sick people to have marijuana. On the other hand, pot grown for medicinal purposes in an abandoned Manitoba mine with Ottawa's sanction sits in storage.
In Britain, under a proposal due to become law next year, simple possession of a small amount of cannabis will no longer result in an automatic arrest although police will still be able to go after users in "aggravated" circumstances, such as smoking in the presence of children. Cannabis trafficking will also continue to bring a prison sentence.
Meanwhile, clinical studies on the use of marijuana for medicinal purposes are under way with HIV patients in Canada and with people suffering from multiple sclerosis in Britain.
The British Lung Foundation says it is not trying to get involved in the debate over whether cannabis should be legalized, leaving that to politicians. "Our report is not about the moral rights and wrongs of cannabis, but simply making sure everyone is completely clear about the respiratory health risks involved," said Dr. Mark Britton, chairman of the foundation.
Dr. Russell says he recently saw a 40-year-old patient in his clinic with "severe end-stage emphysema" and has about 18 months to live. The patient has been smoking three joints a day for the past 25 years, the equivalent of smoking 60 cigarettes a day from the age of 15, he says.
Studies of heavy cannabis smoking among Rastafarians in the Caribbean have also pointed to increased danger of early lung cancer, Dr. Russell says.
Les Iversen, a professor of pharmacology at King's College in London and an expert on cannabis, agrees that smoking marijuana poses dangers, but he says the report's findings are exaggerated.
There is no specific evidence linking cannabis smoking with lung cancer, Prof. Iversen says.
He says it's absurd to say smoking three joints is equivalent to smoking 20 cigarettes because joints come in different sizes and strengths as do commercial cigarettes.
Although he adds, "I don't think any drug is safe."
Psychiatrists have also linked cannabis use to schizophrenia.
"People with schizophrenia do not take more alcohol, heroin or ecstasy than the rest of us, but they are twice as likely to smoke cannabis regularly," says Dr. Robin Murray, a professor of psychiatry at the Institute of Psychiatry in London.
Dr. Murray says cannabis, along with cocaine and amphetamines, encourage the release of dopamine in the brain, which in turn leads to increased hallucinations.
He notes that the incidence of schizophrenia in south London has doubled in the past 40 years, and he says increased use of both cannabis and cocaine could be at fault.
Dr. Murray cites a study that interviewed 50,000 conscripts to the Swedish Army about their drug use and followed up later. Heavy users of cannabis at the age of 18 were six times as likely to be diagnosed with schizophrenia by the time they were 33 than those who kept away from the drug.
Another study, this one in the Netherlands, interviewed 7,500 people about their consumption of drugs and looked at their behaviour over the next three years. Regular users of cannabis were more likely to develop psychosis than those who did not use the drug.
"Any public debate on cannabis needs to take account of the risks as well as the pleasure," Dr. Murray says. "Pro-marijuana campaigners claim, extrapolating from their Saturday-night joint, that cannabis is totally safe. Yet they would be unlikely to claim that a bottle of vodka a day is healthy on the basis of sharing a bottle of Chablis over dinner.
"No drugs that alter brain chemistry are totally safe," he says. "Just as some who drink heavily become alcoholic, so a minority of those who smoke cannabis daily go psychotic."
A major study on the links between cannabis and schizophrenia is due to be published in the British Medical Journal next week by Louise Arsenault, a biomedical researcher at the Institute of Psychiatry who was trained at the University of Montreal.
Research made public last year by Dr. Arsenault showed that young men who regularly smoke cannabis are five times more likely to be violent than those who avoid the drug. Using data from a study of 961 young adults in Dunedin, New Zealand, she discovered that one-third of those with a cannabis habit had a court conviction for violence by the time they hit 21 or had displayed violent behaviour. That was three times the level of those who drank excessive amounts of alcohol.
The warnings about marijuana have not deterred members of Britain's Legalize Cannabis Alliance, who say the report is merely a selective study of existing medical literature, which ignores studies that discount the health threats posed by the drug.
"I've used it for 30 years and it doesn't seem to have affected my health," says Alun Buffry, the alliance's national co-ordinator.
"I stopped tobacco three or four years ago and I have noticed that since then my health has improved. My general level of energy has improved and I get more of a high from cannabis than the sleepiness I used to get, which I think had to do with tobacco."
Mr. Buffry argues that it would be best to legalize cannabis to control the quality of what is sold and eliminate "dirty supplies" that may include potentially harmful glues, fillers and colouring agents.
"I would argue that it would be far more dangerous illegal than it would be legalized," he says. "Even if cannabis were the most dangerous substance in the world, it is still consumed by millions of people."
Alan Freeman is The Globe and Mail's European correspondent.