The following is transcript from yesterday's "Health Report" on Radio National
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Norman Swan: Hello and welcome to the Health Report with me, Norman Swan.
And before you get too excited about the medicinal uses of cannabis, we bust some myths and call a spade a spade, including the issue of cannabis addiction.
Professor Jan Copeland has just co-authored a book on quitting cannabis. Jan is director and founder of the National Cannabis Prevention and Information Centre at the University of New South Wales.
Jan Copeland: The myths are rife, and unfortunately as my time has gone on in this field (it's now over 25 years) the mythology around cannabis has grown rather than diminished.
I think the strongest myth is that it's not addictive. Certainly that is well addressed in the book. But there's a number of health effects that are promulgated that are really poorly evidenced based, things such as 'it's good for asthma', 'it cures cancer' is now something I regularly hear in the media, which is very distressing and disturbing because of its implications for people abandoning conventional healthcare and taking up cannabis smoking as an alternative. Driving is a big myth that has persisted for many years. We have a much better idea of what the relationship is and we know that, yes, you do drive more slowly but…
Norman Swan: You don't necessarily drive more safely.
Jan Copeland: Absolutely not, no. And unfortunately that has translated into accidents and deaths.
Norman Swan: And we've covered this before on the Health Report, that even though there is a bit of a bandwagon now about the medical uses of marijuana, the evidence-base for that is pretty thin too.
Jan Copeland: It is, and we don't review that in this book but it's available on our website if people are interested. We have done a review of that literature, and most of it is actually based on synthetic THC.
The literature on whole smoked plant material is almost non-existent and there is no human clinical trials of the plant.
Norman Swan: And THC is tetrahydrocannabinol, which is one of the active ingredients of cannabis.
Jan Copeland: Yes, that's the part of cannabis that gets one stoned, but there is another very important cannabinoid, cannabidiol, CBD, and we are doing some research with that at the moment. It doesn't get you stoned and it has the opposite effects to THC, so it reduces anxiety, reduces symptoms of psychosis, and we are looking to see if it helps cannabis withdrawal.
Norman Swan: What are the known health and psychological effects of cannabis at what sort of dose and what sort of frequency and what sort of age of onset of use?
Jan Copeland: There's a number of things that affect whether or not people go on to develop dependence, the level of exposure to the drug is pretty obviously one of the most important ones, the more frequently people use…
Norman Swan: But age of exposure is important too.
Jan Copeland: Absolutely, and that was my next point, that the other very important point is when your brain is first exposed to the drug. And there's something about the developing brain in adolescents that exposure, particularly before the age of 17, is much more likely to lead to a whole range of problems, including dependence. That's the addiction potential of cannabis. Of anyone who has ever smoked it's about one in 10, for alcohol it's about one in eight for example, nicotine about one in three. But when people start smoking early, that more than doubles that risk of developing an addiction. People who are smoking daily, they've got about a 50% risk of meeting criteria for dependence. So daily smoking is a very big red flag, and that's something that we see in our treatment populations, they've almost always been at least six-plus times a week smokers, and they've been doing that for a long time by the time they get into treatment.
Norman Swan: And what about the dose at each sitting, or lying as the case may be?
Jan Copeland: Couching! There's just not the studies to know that because we don't know what the potency is of the cannabis, but we do know that the potency of cannabis has dramatically increased over the last few years, and particularly in the US where the very, very high potency products are now available through the medicinal cannabis legislation.
Norman Swan: And what about psychosis and other psychological effects?
Jan Copeland: What we know about cannabis is it about doubles the rate of developing schizophrenia. The timing is right, they smoke cannabis typically before they develop schizophrenia…it's dose-related…
Norman Swan: And the prevalence of schizophrenia in high cannabis use populations such as Brixton in London is much higher, it's more than 1%.
Jan Copeland: Yes, as you rightly point out, in South London and other places where cannabis use has gone up, the rates of schizophrenia have also gone up.
Norman Swan: And what about the heart and lung?
Jan Copeland: Yes, we are learning much more about that, and it's more concerning as the population ages. The 50-pluses are the fastest growing group of cannabis smokers in the population…
Norman Swan: Ageing hippies, or ageing normal people because it's almost normal to be smoking cannabis.
Jan Copeland: Well, that's another myth; 90% of the population didn't smoke cannabis in the previous year, but yes, certainly people have that impression, but of course it's within certain groups. But yes, when you talk about heart and lung and stroke we are seeing cases of young cannabis users experiencing strokes and heart disease…
Norman Swan: Independent of the tobacco that they mix the cannabis with?
Jan Copeland: Yes. There is now a series in the pathology reports of cannabis associated deaths. And when they've put a halter monitor on a young man as he inhaled…
Norman Swan: It measures your heart rate, your heart rhythm I should say.
Jan Copeland: Yes, to monitor his heart over 24 hours, as he inhaled cannabis his heart stopped for over six seconds. So that was an indicator of what might be the cause of death in some of these people. But the risk of having a heart attack in the first hour of smoking is seven-fold that of periods where you are not smoking.
Norman Swan: Years ago they used to talk gently about cannabis dependence, and you are unreservedly using the word 'addiction'. First of all, what is the difference between dependence and addiction?
Jan Copeland: There is no difference. The American Psychological Association changed it to 'dependence' because of this notion that addiction was moralising or judgemental a term, but now the DSM-5, which is the bible for the mental health field, has gone back to using the term 'addiction'. And I think it resonates much more clearly with the general public, they understand that term, and it has led to misunderstandings where the cannabis lobby group has said, 'Oh well, it might cause dependence but that's not addiction,' and that's false.
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More at
http://www.abc.net.au/radionational...th-risks-of-using-cannabis/6057934#transcript
(Bolding is mine.)