The case for cannabis oil must be based on science, not emotion

The debate is complex, in part because it is muddled with campaigns to legalise cannabis for recreational use, but also because of poor reporting on the science of medical cannabis.

For that reason, it is worth going back to basics. The psychoactive chemical in cannabis is delta-9-tetrahydrocannabinol, or THC. This is the chemical that gets you high. The THC ‘resin’ content of the plant is concentrated around the flowers, which are illegally sold for recreational purposes either dried, or with the resin extracted into a block. You can buy this stuff from a dealer and smoke it.

There is also a non-psychoactive chemical in cannabis called CBD, which does not get you high. This is important for understanding the medical debate, because both THC and CBD are considered potentially interesting for medicine. Doctors can and do prescribe cannabis for medical purposes, but in the UK that is pretty much limited to two products, against a background of strict regulation.

Although laws for both recreational and medicinal use of cannabis are the responsibility of EU member states and differ by country, at the moment the European Medicines Agency only approves Sativex (a British-made product), a cannabis spray containing both CBD and THC from the flower of the plant, and – importantly – recommends it only for the treatment of multiple sclerosis.

England and Scotland allow private prescriptions for Sativex, but not NHS prescriptions (Wales very rarely allow it). This is because the National Institute for Health and Care Excellence (NICE), the body which advises which medicines should be funded by the taxpayer, reviewed the evidence and found Sativex insufficiently effective for its price (in clinical trials it only works for about half of participants, and is very expensive).

NICE also approves the use of a synthetic cannabinoid called Nabilone, but only for chemotherapy patients who do not respond to other anti-nausea drugs. Neither Sativex nor Nabilone are approved for children, and that would likely be the case even if medicinal cannabis were legalised for other conditions.

This is where we get to the clash. While campaigners insist that cannabis oil has been miraculous in treating symptoms or even curing illnesses completely, scientific consensus says otherwise. Anecdotes are useful starting points, but they are not evidence, and currently there is insufficient evidence to support making cannabis oil available more widely on the NHS.

There is new headline-making research which indicates cannabis oil might work to control seizures for patients with the rare conditions Lennox-Gastaut syndrome (LGS), and Dravet syndrome, but this does not mean it’s going to be approved as a treatment. More testing needs to happen to ensure the cannabis oil does not adversely affect the other, proven medicines those patients are on. It’s a long, slow process and there are no overnight answers despite what campaigners insist. There are no miracle cures.

However, a web search for ‘cannabis oil cancer’ brings up a slew of websites claiming exactly that. These pro-cannabis websites declare that symptoms disappear overnight or cancer goes away entirely. Such claims are illegal under the UK’s Cancer Act, but could easily entice desperate patients who aren’t familiar with the practice of pseudoscience, in which science-sounding language is used to try to legitimise unscientific claims.

The issue is confused further by the availability of retail cannabis oil. This is the stuff you can buy from health food shops and supermarkets. It’s legal because it doesn’t really have any cannabis in it. Usually derived from hemp seeds, retail cannabis oil contains a very low amount of CBD (around 0.05%) but zero THC. This type of oil will not get you high, but neither will it cure your cancer or any other illness.

Indeed, it is illegal to sell CBD oil in the UK as medicine. It can only be sold as a food supplement, and this is because the evidence for it having any medicinal value is poor. At best it might work as an expensive placebo.

Charlotte Caldwell was, until recently, selling CBD oil under the brand ‘Billy’s Bud’, named after her son. The website has now been taken down, but an archive shows claims of medical efficacy which are not backed by scientific consensus. (It is not clear if the Caldwells intend to also sell THC cannabis oil should the government respond to pressure to make it legal).

So, retail cannabis oil isn’t medicinal, has only trace amounts of CBT and no THC at all, and shouldn’t be sold as having any medical benefits. Medicinal cannabis, the stuff of prescriptions, is different. Across Europe, the medicinal cannabis that can be prescribed is in capsules, spray, or sometimes dried flowers for making ‘tea’. No doctor in Europe is legally allowed to prescribe cannabis for smoking, not least because it would be impossible to control the dose, but also because inhaling burning particles is pretty bad for your health. These policies are the result of evidence, not anecdote.

This is exactly how policy and NHS drug approval should work, but public and political opinion on morally-complex medicine is currently being influenced not by evidence but by a highly emotional media rhetoric driven by a few individual and upsetting cases such as Billy Caldwell, Alfie Evans, and Charlie Gard.

It is difficult to criticise the media in these cases without sounding unsympathetic to the devastating plight of the individuals concerned. But much of the coverage in these sorts of instances revolve around individual patient or family anecdotes which, while compelling, are no different to the testimonies of those using discredited or unproven alternative treatments like homeopathy, which has recently been de-funded by most NHS trusts despite the protests from patients who insist it works for them.

The debate about the legalisation of cannabis is often polarised because of stereotypes around who smokes weed, and what effect it has on society. Most people have an opinion on the issue, although not always an informed one, and politicians are no exception. British governments, of all stripes, do not have a great record when it comes to science evidence in policy-making.

Drug laws have historically been the result of international pressure and moral panic, rather than actual harm caused by legal substances, like alcohol or tobacco.

In 2009, government science advisor Prof David Nutt was sacked from his advisory position for attempting to promote an evidence-based approach to drug classifications, rather than a political one (the government considered this a conflict of interest, with the then Home Secretary Alan Johnson telling the Guardian, ‘he was asked to go because he cannot be both a government adviser and a campaigner against government policy’).

Good medicine is not usually based on media hysteria around individual cases or even individual scientists, but on evidence and consensus. Indeed, one of the biggest contemporary public health challenges is the growing movement against vaccines, fuelled by the now wholly-discredited researcher Andrew Wakefield, whose 1998 paper (since declared fraudulent by the medical community) was widely reported as having proven a link between the MMR vaccine, and autism. No such link exists, but the harm has been done. Vaccine rates have dropped, and measles, mumps and rubella cases are on the rise. If the government had bowed to media and public pressure to outlaw the MMR jab, the harm would be even worse.

This is why any attempt to expand medicinal cannabis prescribing in the NHS must be considered carefully, and only on the basis of clear clinical evidence, which is currently absent.

Of course, absence of evidence is not evidence of absence. Just because the studies so far don’t prove that cannabis oil works, that doesn’t mean it can’t work. It’s precisely because cannabis is illegal that clinical researchers struggle to test it. Simply reviewing the current evidence, as Sajid Javid has agreed to, is not sufficient, because there isn’t much evidence to review.

If the government is genuinely committed to the medical cannabis issue, it must support and fund more research. If that research shows that cannabis oil works and is good value for the NHS, then it absolutely should be legalised. This is where it’s vital to separate anecdote and media-driven emotion from clinical evidence, as heartless as that may seem. Medicine is not approved or funded by the NHS because some patients want it, but because it does something, and does it well for the money. And when it comes to cannabis oil, the jury is still very much out.

Tracy King is a writer, debunker, and science animation producer