Researchers at the University of Bath, led by Dr Rachel Lees Thorne, and members of the Bath MHRG team, lead Prof Tom Freeman and Dr Lindsey Hines, worked on the project. They have developed a new way to help people understand how strong their cannabis is and how much they are using.

Cannabis has become much stronger over time, and many people don’t realise how much THC, the main active ingredient, they are consuming. This can increase the risk of harm, including dependence and mental‑health difficulties.

The team has proposed a simple “cannabis unit” system, similar to alcohol units, to help people keep track of their use and make more informed choices.

Why is this important?

Cannabis is widely used, but there’s no clear guidance on safe levels.

These thresholds could help:

• Consumers make informed choices.
• Clinicians & public health bodies communicate risks.
• Legal markets improve product labeling (e.g., Canada is considering THC units on labels).