A recent study from researchers at the University of Bath in the UK proposes that establishing a standardized unit for measuring cannabis potency—much like standard drinks for alcohol—could help individuals manage their intake and highlight those at risk for cannabis use disorder.
With more countries introducing laws permitting both medicinal and recreational cannabis, such metrics could play a crucial role in informing public health approaches focused on harm reduction.
“As cannabis becomes more widely available in legal markets globally, it’s increasingly important to aid consumers in making informed decisions about their usage,” says Tom Freeman, a senior author and Director of the Addiction and Mental Health Group at the University of Bath.
While some individuals may indulge occasionally, others may fall into cannabis use disorder (CUD), leading to dependence, mental health issues, tolerance, risky behaviors, impaired cognitive function, and difficulties in relationships and financial stability.
Currently, both users and healthcare professionals face challenges in quantifying cannabis use, primarily due to its long-standing illegal status and unregulated production—issues that persist in many regions today.
While we understand that frequency and amount correlate with risk for cannabis disorder, we often overlook the potency of the active compounds.
“Cannabis potency (the percentage of tetrahydrocannabinol or THC) has been on the rise for several decades, with higher potency linked to increased risks, including CUD and negative mental health consequences,” the researchers detail in their published findings.
In their study, which analyzed data from 150 adult and adolescent cannabis users in London over a 12-month period as part of the four-year CannTeen study, the team was able to estimate potency in standard THC units.
Interestingly, not all joints are equal. For example, a 0.45-gram joint of potent herbal cannabis can contain around 12.78 standard THC units, while a weaker version might only contain 3.78 THC units.
Previous studies have explored similar methods of quantifying cannabis use beyond sheer weight and frequency. This latest research builds on past findings, concluding that evaluating usage in standard THC units effectively assesses an individual’s risk for developing cannabis use disorder.
The study suggests that to minimize the chances of developing cannabis use disorder, adults should keep their consumption below 8 THC units per week. In fact, 70% of adults who exceeded this threshold in the CannTeen study reported experiencing cannabis use disorder.
“The primary aim of our guidelines is to mitigate risk,” explains Rachel Lees Thorne, the lead author and a psychology researcher at the University of Bath.
“The only completely safe level of cannabis use is none at all. However, for those who wish to continue using cannabis or feel unable to stop, we want to facilitate ways for them to reduce potential harm—like opting for lower-THC products or cutting back on their usage.”
Public health experts have welcomed these findings, noting that a standardized measure of THC consumption could empower individuals to regulate their intake and support research efforts.
Still, psychiatrist Marta Di Forti from King’s College London reminds us that “cannabis, unlike alcohol, has more than 144 cannabinoids, not just one active component.” Yet, she acknowledges, “THC units are undeniably a significant and necessary beginning.”
The research appears in the journal Addiction.
