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Wednesday 14 May 2008

RAPID ROUNDUP: Cannabis use and cardiovascular risk (Molecular Psychiatry) – experts respond.

According to the 2007 National Drug Strategy Household Survey, in 2007 one in three (about 5.8 million) Australians aged 14 years or older had used marijuana/cannabis at some time in their lives. Of the same Australians, almost one in ten (1.6 million) used marijuana/cannabis in the previous 12 months. The long term effects of marijuana are still hotly debated, and new research out today in Molecular Psychiatry suggests that marijuana may affect the chemistry of the blood leading to long term problems such as heart attack and psychosis. Stimulation of cannabinoid receptors in the liver by THC, the active ingredient of marijuana, leads to an increase levels of a protein known as apolipoprotein C-III, in the blood. Too much of this normally harmless protein, reduces the breakdown of certain fatty acids and can produce short-term effects such as cardiac disorders and decreased blood flow to the cerebral vasculature.

The AusSMC has rounded up Australian experts to comment on this research .

Feel free to use the comments below in your stories. If you would like to speak to an expert, or need a copy of the paper and press release, please don’t hesitate to contact us on (08) 8207 7415 or by email.

Dr Jonathon Arnold is Head of the Cannabinoid Research Group at the University of Sydney. He is an internationally-recognised researcher in the pharmacology of cannabis and the cannabinoids (cannabis-like drugs).

“A newly approved cannabinoid (cannabis-like) drug in Europe, Rimonabant, is an anti-obesity agent that reduces blood levels of factors that increase risk of cardiovascular problems. Interestingly, rimonabant acts opposite to compounds found in marijuana like delta9-tetrahydrocannabinol. So this paper by Dr Jean Lud Cadet's group provides evidence consistent with this - chronic marijuana smoking increases levels of apolipoprotein C-III, something that might increase a person’s risk of cardiovascular disease. This finding justifies closer inspection of the effect of cannabis on the development of cardiovascular disease - a phenomenon not clearly supported by the scientific literature. However, going further and linking marijuana's effect on apolipoprotein C-III with neurological disease remains highly speculative and without any strong supportive data.”

Dr Alex Wodak is Director of the Alcohol and Drug Service, St. Vincent's Hospital Sydney.

“This is one of a multitude of well funded studies which appear regularly and frequently from the US government centre for research on illicit drugs. These studies invariably suggest mechanisms that might cause cannabis to damage health. It is not clear that the abnormalities reported in this paper would necessarily result in any clinically significant impairment. Major epidemiological studies suggest only modest physical harm from cannabis. If cannabis is thought to cause severe health problems, it seems strange to choose policies which inevitably result in control of the drug passing to criminals and corrupt officials. Alcohol and tobacco are responsible for 97% of all drug related deaths in Australia and the fact that these drugs are taxed and regulated has enabled governments to reduce alcohol consumption by 25% from 1981 and reduce smoking prevalence substantially.”

Dr David Caldicott is an emergency doctor and independent drug expert based in Adelaide.

“In 2005, our research group published the case of a 19 year old man who had a heart attack following the use of marijuana. In that paper, we offered a number of theories as to how marijuana might have contributed. Jean Lud Cadet and his colleagues offer another piece of evidence in the puzzle as to why some young people suffer serious - and indeed sometimes fatal - consequences from using a drug most often considered by the consumer as benign. Our biochemistry is as individual as our fingerprints, and this applies to the enzyme systems that produce the protein ApoC-III. This individuality may explain why not all marijuana consumers seem to be affected- but it has been very difficult to tell which consumers could be at risk. In an environment where there are increasing calls for the use of therapeutic marijuana, we are reminded that no substance or drug, medical or otherwise, can ever be considered totally ‘harm-free’. Future research, based in part on research such as this, could even result in a blood test that could predict which patients could be safely treated with medical marijuana.

“Perhaps even more important than the particular facts of this intriguing paper is the general example it shows regarding the value of dispassionate, scientific research in contributing to the debate on illicit drugs. This information will be directly evaluated by many Australian consumers. The last decade of the drugs debate in Australia has been irrevocably tarnished by moral indignation and unsubstantiated rhetoric. The facts regarding drug use, and the manner in which they are reported, are far more persuasive to young consumers than the mere speculation of politicians. If supported, equally persuasive research can and should be produced in Australia.”

Professor Wayne Hall is a Professorial Research Fellow in the Division of Health Systems, Policy and Practice, at the University of Queensland. He was previously Director of the National Drug and Alcohol Research Centre at the University of NSW (1994-2001). He has been an expert adviser to the World Health Organization since 1993, advising on: the health effects of cannabis use; the effectiveness of drug substitution treatment.

“This study is all too typical of laboratory studies of the health effects of cannabis. It uses a very small sample of marijuana users and controls who are compared on multiple biological endpoints using gee-whiz new forms of biological analysis; it finds differences between the two groups that probably will not be replicated in future studies (because findings in studies that conduct multiple comparisons are often not replicated); and the author fail to consider plausible alternative explanations of the association (assuming for the moment that the result is replicable), namely, that heavy cannabis users consume more junk food than controls because of appetite stimulating effects of THC which are well known to users and one of the reasons why the cannabinoid antagonist rimonabant which they cite in support of their finding) seems so useful in reducing weight and symptoms of the metabolic syndrome in obese subjects. The main value in making media comment on this article would be in educating journalists and the public to be more skeptical of such studies.”