Following her appearance before the Home Affairs select committee yesterday, I have written to Professor Gerada raising a number of issues. A copy has been sent to the committee.
Dear Professor Gerada,
I watched your evidence to the Home Affairs select committee yesterday with great interest.
1. I thought the most telling point you made was:
"I don't see a lot of problem cannabis users...we're not seeing a lot of cannabis users presenting for treatment"
I hope that this will carry a great deal of weight with the committee when it considers the wisdom of continuing to spend £500 million each year on the criminal justice system solely on enforcement of the cannabis laws. (ref.1)
2. However, I was very concerned when you said:
"Cannabis is not a particularly good drug to be on. It causes lung cancer. It causes oesophageal cancer. It causes failure at school. It's an addiction in its own right."
It is a moot point as to whether it is good to be on any drug except for therapeutic use. However, as most of us do use drugs to some extent, alcohol, tobacco or caffeine, such discussion is only meaningful when it considers comparative harms. In these terms, would you agree with Professor Les Iversen, chair of the ACMD, that "cannabis is one of the safer recreational drugs"?
2a. On the question of whether cannabis causes lung or oesophageal cancer, I would be interested in what evidence you can present to support this claim. Most studies of the effects of cannabis smoking fail to control for the carcinogenic effects of the tobacco with which it is usually mixed.
The central theme of our "Tokepure" harm reduction campaign is that the most dangerous thing about cannabis is smoking it with tobacco. (ref.2)
The best evidence about cannabis and lung/oesophageal cancer is the study by Dr Donald Tashkin of UCLA in 2006, the largest ever case-control study of its type, which concluded that "smoking marijuana, even regularly and heavily, does not lead to lung cancer". Dr Tashkin is reported as extending this conclusion to say that "Marijuana smoking also did not appear to increase the risk of head and neck cancers, such as cancer of the tongue, mouth, throat, or esophagus" (ref.3,4,5)
This conclusion was supported by a 20 year longitudinal study published this January in the Journal of the American Medical Association which concluded that "marijuana use was not associated with adverse effects on pulmonary function" (ref.6)
Therefore, I can't see that your claim that cannabis causes lung or oesophageal cancer is supported by the evidence. Can you agree with me on this or can you provide evidence that supports your assertion?
2b. As to whether cannabis causes failure at school, it is self-evident that the recreational use of any psychoactive substance is not going to assist with education. One of the main criteria for any model of cannabis regulation would be to restrict its use to adults only.
2c. On cannabis "addiction", the evidence is that dependence (at about 9% of users) and severity of withdrawal symptoms are approximately equivalent to those of caffeine. (ref.7). Furthermore, GW Pharmaceuticals recently reported on phase III trials of Sativex, its 51% THC skunk cannabis tincture that "...the drug does not appear to lead to withdrawal effects if patients suddenly stop using it." (ref.8)
3. I know you were not asked about the therapeutic benefits of cannabis but I was disappointed that you did not take the opportunity to enlighten the committee. The peer reviewed evidence confirming the efficacy of cannabis as medicine for a wide range of conditions is now overwhelming. (ref.9) This sets cannabis apart from all other drugs which the committee is considering. It is vital that they are apprised of the latest evidence.
Apart from GW Pharmaceuticals, British doctors lag far behind the rest of the world in this field, particularly GPs. At CLEAR we receive frequent reports of GPs whose interest in cannabis as medicine is swiftly suppressed by the health authorities. Meanwhile, throughout the rest of Europe, the US and Israel more and more patients benefit from cannabis as medicine. Britain needs to catch up!
The importance of the endocannabinoid system in physical and mental health is now beyond doubt. As it was only discovered in 1988, many currently practising doctors will have received no training on the subject but for the purposes of the committee it is important that they are properly informed. May I ask if you would consider providing them with such evidence?
Thank you for taking the time to read this letter and I would be grateful for a reply.
cc. Home Affairs select committee, inquiry into drugs policy