Cannabis Safety Threshold: British Scientists Propose Weekly Limits

British scientists have proposed setting an upper reference limit for weekly cannabis consumption, as is done with alcohol. Given that the best way to avoid harm from cannabis use is not to use it, a group of British scientists thought that reference guidelines could be established to reduce the most dangerous consequences of its overuse – a maximum limit not to be exceededas is already done with alcohol. The idea, illustrated in a study published in the scientific journal Addictionis that new parameters based not on the frequency of cannabis consumption, but on the THC content of the substance smoked, can inspire more responsible use in those who simply cannot (or cannot) abstain. Power, not frequency The idea of ​​researchers at the University of Bath, in the United Kingdom, is to use a system for measuring cannabis consumption based not on the weight of marijuana (the dried flowers of cannabis, which contain a greater quantity of active ingredients, including THC) nor on the frequency of use of the substance, but on its content of THC or tetrahydrocannabinol, its main psychoactive compound. Measuring consumption in THC units – the equivalent of alcohol units, but for cannabis – would make it easier to quantify the potency of cannabis and its psychotropic effect. What is the limit, then? Just as the threshold for moderate alcohol consumption is by definition no greater than 2 alcoholic units per day at most, for men, and one at most, for women (where one alcoholic unit corresponds to 12 grams of ethanol, contained in a 330 ml can of beer), and therefore a maximum of 14 alcoholic units per week, for cannabis the researchers identify a maximum limit of 8 units of THC per week: the equivalent of approximately 40 milligrams of THC, or one third of a gram of herbal cannabis. Above this threshold there is a higher risk of developing cannabis use disorder or cannabis dependence, the inability to stop the continued use of cannabis which affects approximately 22% of people who consume it regularly, and which manifests itself with symptoms with the physical and psychological symptoms of withdrawal (insomnia, mood disorders, time wasting and risky behavior in order to obtain the substance). Scientists have calculated that 80% of cannabis users who stay below the threshold of 8 units of THC per week do not develop cannabis use disorder, while 70% of those who exceed this threshold do. “The ultimate goal of our new guidelines is to reduce harm” clarifies Rachel Lees Thorne, a researcher from the Department of Psychology at the University of Bath, one of the authors of the study. «The only truly safe level of cannabis use is non-use. However, for those who don’t want to quit or aren’t able to, we still want to make it easier to reduce the risks. For example, a person might decide to use products with lower THC content to reduce the amount of cannabis used.” The findings will be of particular interest in countries where the sale and consumption of cannabis have been legalised: for example, Canada, which is working to include clear indications of THC units contained on the labels of cannabis products, as is done today for alcohol in some countries (including the UK).