Adults consuming more than about 8 standard THC units (40 mg THC) per week face elevated risk of cannabis use disorder, with adolescents at risk from even lower amounts.
Public health policymakers, harm reduction advocates, cannabis regulators, addiction prevention specialists
What the researchers found
Weekly THC consumption discriminated CUD risk with good accuracy (AUC >0.70). Risk thresholds for any CUD: 8.26 units/week for adults and 6.04 units/week for adolescents. For moderate/severe CUD: 13.44 units/week for adults and 6.45 units/week for adolescents (1 standard unit = 5 mg THC).
Why it matters
Just as alcohol has standard drink guidelines, cannabis needs evidence-based consumption thresholds. This study provides the first THC-unit-based risk estimates that could underpin safer-use guidelines.
The numbers in context
Adults: any CUD risk threshold at 8.26 units/week (41.3 mg THC), moderate/severe CUD at 13.44 units/week (67.2 mg THC). Adolescents: any CUD at 6.04 units/week (30.2 mg THC), moderate/severe CUD at 6.45 units/week (32.3 mg THC). AUC >0.70 for all models.
How the study worked
Longitudinal observational data from the CannTeen study with five assessments over 12 months. 65 adults (26-29) and 85 adolescents (16-17) in London. Weekly standard THC units estimated via Enhanced Cannabis Timeline Followback. CUD diagnosed via DSM-5 at final follow-up.
What this study cannot tell us
Relatively small samples (65 adults, 85 adolescents). London-specific population may not generalize globally. 12-month follow-up may not capture long-term CUD development. Standard THC units require accurate potency knowledge.
How to read the evidence
Longitudinal design with validated measures and good discrimination accuracy, limited by small sample sizes and single geographic setting.
When this study was published
Published 2026, using 2022-2023 CannTeen study data from London.
The bigger picture
Alcohol has standard drink guidelines. Cannabis has had nothing comparable — until now. These THC-unit thresholds could form the basis for lower-risk cannabis use guidelines similar to those that have helped reduce alcohol-related harm.
Questions still open
- Would these thresholds hold in larger, more diverse populations? How do consumption patterns (daily low vs. weekend high) affect risk at similar weekly totals? Can standard THC unit labeling be implemented on cannabis products?
Common questions
How much cannabis is too much per week?
What is a standard THC unit?
Read the original research
Estimating thresholds for risk of cannabis use disorder using standard delta-9-tetrahydrocannabinol (THC) units.
Addiction (Abingdon, England)
Citation
Lees Thorne, Rachel; Lawn, Will; Petrilli, Kat; Trinci, Katie; Borissova, Anya; Ofori, Shelan; Mokrysz, Claire; Curran, H Valerie; Hines, Lindsey A; Freeman, Tom P. (2026). Estimating thresholds for risk of cannabis use disorder using standard delta-9-tetrahydrocannabinol (THC) units.. Addiction (Abingdon, England). https://doi.org/10.1111/add.70263
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