David Kendall and Michael Randall call for more research on the use and effect of cannabis
The debate about cannabis encompasses a melange of issues, ranging from potential medical benefits to civil liberties.
The latest issue to emerge stems from the discovery that the body manufactures its own cannabinoids (endocannabinoids) that produce similar effects to chemicals contained in the cannabis plant. Many people are now keen to carry out research into this family of chemicals.
Endocannabinoids appear to be important regulators - playing a part in controlling people's pain, in the immune system, in governing the flow of blood and in sleep. Indeed, it would be surprising if defects of endocannabinoid function were not involved in some illnesses. Many pharmaceutical companies have in fact had research programmes based on cannabinoids running for years but progress in our understanding of how they work has been slowed by the stigma of association with illegal drugs.
What is known is that herbal cannabis is a complex mixture of active cannabinoids and pharmacologically inert plant products that, when smoked, increase in complexity still further.
Although the use of such a mixture as a medicine is far from ideal, some patients suffering from chronically painful diseases such as multiple sclerosis have reported that they derive more benefit from smoking a joint than from taking the synthetic cannabinoid Nabilone, which is licensed in the UK only to prevent nausea in cancer patients.
In the light of such reports, last year a committee of the House of Lords called for clinical trials on the effects of cannabis on patients suffering from illnesses such as multiple sclerosis.
So how safe is cannabis? It is certainly not a dangerous drug in the pharmacological sense and no deaths have been documented as a direct result of cannabis ingestion. Its use has been linked to impaired driving and to road accidents, but the same is true of many prescription and over-the-counter medicines. In fact cannabis is many times safer than alcohol or tobacco.
Paradoxically, opiate drugs such as heroin, which are highly toxic, can be prescribed as medicinal remedies in the United Kingdom despite their illegal use by drug abusers. In this context, it is difficult to understand the official resistance to its medicinal use.
But, while cannabis has undoubted medical potential, like any drug it has drawbacks. The act of banning cannabis has, paradoxically, led some proponents of its use to overestimate its medicinal value. If we are to exploit the medicinal properties of cannabinoids, then there must be a concerted research effort to understand how they work, and clinical trials to test their effectiveness.
Taking a home-grown herbal remedy of low toxicity and some medicinal value to combat chronic pain seems to be a poor reason for prosecution under the controlled drugs regulations. But in the present political climate, in which no party can be seen to be "soft on drugs", such prosecutions will probably continue.
The official government line appears to be that cannabis is a "gateway" drug that inevitably leads users to consume hard drugs. If that is so, it is at least partly because seeking cannabis brings users into contact with dealers in truly dangerous drugs.
In reality, recreational drug consumption is a more complex behaviour than a straightforward progression from alcohol and tobacco to cannabis and thence to heroin and ruin. Along with medical trials, support should be given to large-scale research into the sociology of cannabis use before the debate degenerates further into uninformed argument.
David A. Kendall is reader in molecular pharmacology, and Michael Randall is senior lecturer in pharmacology, University of Nottingham Medical School. Their opinions do not necessarily reflect the view of the University of Nottingham.
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