Experts call for alcohol-style unit system for grading THC strength of cannabis

A unit system for cannabis similar to the one used for alcohol could improve the mental health of users, according to experts.

Researchers say more needs to be done to make people aware of the dose of Tetrahydrocannabinol (THC) – the drug’s main psychoactive component – they are consuming.

The group, from the Addiction and Mental Health Group at the University of Bath, King’s College London, UCL and the Australian Catholic University, suggest a unit level should be set at 5mg of THC.

Previous research from the team at the end of 2018 highlighted how concentrations of THC in cannabis have doubled across Europe over the past decade.

Writing in the journal Addiction, the researchers show that in countries where cannabis is legally sold, such as Canada, the number of standard units a product contains could easily be added to existing packaging labels.

They say introducing an agreed international system could provide a practical guideline for consumers and doctors even in countries such as the UK, where cannabis is illegal.

Dr Tom Freeman (pictured), from the University of Bath, said: “Our findings highlight the need to develop an evidence-based framework to help people use cannabis more safely.

“The current lack of information increases the risk of harm to the consumer.

“Of course the safest level of use for cannabis is ‘no use’.

“Yet, we know that many people across the world regularly consume cannabis so we need to consider how we can better support them in making informed choices and to minimise potential health risks such as addiction or psychosis.

“Where the unit system for alcohol has helped consumers to better manage their alcohol intake, so too do we think this could have important implications for cannabis users.

“Our hope is that the introduction of a system in locations where it is legalised will have knock-on effects to countries where it is not, providing both users and clinicians an important toolkit to guide safer use.”

The research coincides with a second study from the team, published in the journal Psychological Medicine.

In this work, the researchers examined the relationship between using various cannabis products and key health outcomes in more than 55,000 people across 175 countries.

Consumers were asked about the type of cannabis products they used, as well as the severity of problems relating to cannabis use including on their mental health.

Those who typically used higher THC forms of cannabis experienced more severe problems than those using traditional herbal products with lower levels of THC.

Sam Craft, from King’s College London, said: “Our findings add to a growing body of evidence that suggests the health effects of cannabis are dose-related.

“These risks though might be modifiable and we believe that the introduction of a unit system would help both users and healthcare professionals by providing clearer information on the types of cannabis products they consume and their strength.”

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