It's time Britain regulated cannabis like alcohol – the benefits are clear

Most of us want to know how strong an alcoholic drink is before we consume it, which is made simpler by having a standardised system. ABV, or alcohol by volume, is the accepted way of measuring and communicating alcohol potency.

Unlike alcohol, cannabis has no standard measurement of strength. It would be odd to think of only finding out how strong an alcoholic drink is once you’ve already consumed it, but that’s exactly what people who use cannabis have to do.

Although recreational use of cannabis is illegal in the UK, it is hardly a niche activity. In England and Wales, 30 per cent – that’s around 10 million – of adults aged 16 to 64 have tried the drug at least once, according to the annual crime survey. Across the Atlantic millions more have access to cannabis as most US states allow medical and/or recreational use of the drug.

The benefit of regulated markets for American consumers is they are given information about the strength of the cannabis products they can buy. In the main, this is done by suppliers indicating the amount of tetrahydrocannabinol (THC) in their products. So, THC has become the equivalent of ABV for alcohol. Instead of spirits and beers, there are low and high, forgive the pun, THC products.

Having a standard way of displaying the strength of a drug doesn’t just help consumers make purchasing decisions, it can also be used to help them understand risks. For over 30 years, successive governments have advised us on safe levels of drinking by using alcohol units as a standard. Although even with such well-established standards, not everyone is clear about what exactly a unit of alcohol is, let alone whether they heed the advice on the number they should limit themselves to.

Nevertheless, having this standard system allows the evidence of risk to health to be communicated so that individuals have some way of knowing what the safe limit is. And this isn’t just about health, but other critical areas such as driving. Knowing how much alcohol can be consumed to stay the right side of the drink driving laws has also benefited from the standard alcohol unit. Just like alcohol, cannabis carries its own risks to health and other areas of life such as driving.

The shared intelligence from most research into drugs is the rather obvious point that the more frequently a drug is used and in greater quantity, so the risk to health increases. Without a standard cannabis unit, individuals will find it difficult to calibrate whether their use is low or high risk to their health, beyond the generalisation of “don’t use a lot and often”. What constitutes a lot? And how frequent is often? Hourly? Daily? Weekly?

The additional challenge in formulating a standard cannabis unit is that unlike alcohol, there is more than one way of ingesting the drug. Smoking and eating cannabis vary how quickly and intense the effect of cannabis will be. Edible cannabis products have a time delay in their effect which can make it difficult particularly for naive users to work out the amount they need to experience pleasure rather than pain

Dame Carol Black has been appointed by the government to conduct an independent review of drugs in the UK. One of the recommendations she could make is to establish a standard cannabis unit. This would allow public health to advise on what constitutes a safe level of cannabis use in much the same way they do for alcohol. That would move us on from the current failure of advising everyone to abstain, which year after year millions ignore.

Most of us grow out of drug use, we don’t need to be told to refrain. We need a similarly mature approach from politicians that would provide some evidence-based information, like cannabis units, on which we could decide whether we want to use cannabis and if so, how much.

Ian Hamilton lectures in mental health at the Department of Health Sciences, University of York

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