By translating cannabis use into standardized THC units, researchers uncover clear weekly thresholds that signal heightened risk of cannabis use disorder and show that teens may be vulnerable at far lower levels of use than adults.
Study: Estimating thresholds for risk of cannabis use disorder using standard delta-9-tetrahydrocannabinol (THC) units. Image Credit: Tayler Derden / Shutterstock.com
In a recent study published in Addiction, researchers report that weekly cannabis use, measured in standardized THC units, can distinguish individuals with and without cannabis use disorder (CUD), a condition in which cannabis use leads to distress or impairment. In particular, adolescents exhibited lower risk thresholds than adults, suggesting that these individuals are more vulnerable to CUD at lower levels of weekly THC exposure.
What is CUD?
CUD affects about one in five people who use cannabis and is a major public health concern, particularly among adolescents. It can significantly impact quality of life, social relationships, and mental health. Despite greater cannabis potency and widespread use, the cumulative level of cannabis exposure associated with an increased risk of CUD remains unclear.
Previous research has revealed that higher frequency, greater quantity, and stronger cannabis products are associated with adverse health effects. However, many of these studies used frequency-based measures that do not effectively quantify differences in potency and dose.
Inspired by alcohol harm-reduction guidelines based on standard units, researchers have proposed measuring cannabis exposure using standard units of tetrahydrocannabinol (THC), the primary psychoactive ingredient in cannabis. This approach considers both quantity and potency across different products and methods of use, thereby supporting its potential to establish specific THC thresholds associated with the likelihood of CUD.
Monitoring weekly THC exposure in adolescents and adults
The researchers of the current study estimated weekly THC consumption rates. Risk thresholds for CUD in both adolescents and adults were identified using longitudinal data from a 12-month observational study conducted in London, United Kingdom.
The study cohort included 85 adolescents between 16 and 17 years of age, as well as 65 adults between 26 and 29 years of age, who reported cannabis use at least once during the study period. Cannabis use was assessed every three months through a timeline approach, which provided detailed information on product type, potency, quantity, and method of administration.
Cannabis exposure was converted into standard THC units, in which one unit was equivalent to 5.0 mg of THC, and mean weekly THC consumption was calculated across the 12-month study period. The primary study outcome was a past-year diagnosis of CUD, assessed at the final follow-up visit using a structured clinical interview.
Receiver operating characteristic (ROC) curve analyses were conducted separately for adolescents and adults to assess how weekly THC units differentiated individuals with no CUD from those with any form of CUD, including those with moderate or severe CUD.
Optimal thresholds were selected using cut-off values that maximized sensitivity and specificity. All analyses were pre-registered and followed according to established reporting guidelines.
Weekly THC thresholds accurately classify CUD risk
The final analytic sample included 150 participants with complete cannabis use and CUD data. Weekly THC consumption was associated with good to excellent accuracy in identifying CUD across all models, with area under the curve (AUC) values exceeding 0.70. Discrimination was particularly strong in adolescents, among whom AUC values approached 0.94.
For any CUD, the optimal threshold was 8.26 THC units every week in adults and 6.04 units every week in adolescents. These thresholds were characterized by high sensitivity, meaning that most individuals with CUD were correctly identified, although specificity was more modest, particularly among adults.
For moderate or severe CUD, higher thresholds were observed in adults of 13.44 units every week. In contrast, adolescents exhibited a similar threshold of 6.45 units each week to that observed for any CUD diagnosis. Sensitivity analyses confirmed that these results were robust and not influenced by extreme values.
Adolescents showed little separation between thresholds for mild as compared to more severe CUD, indicating elevated vulnerability across CUD severity levels even at relatively low levels of THC consumption. Overall, weekly THC units provided a reliable measure for distinguishing CUD likelihood across age groups.
Conclusions
The current study provides the first evidence-based THC consumption thresholds for classifying the likelihood of CUD, thus indicating the use of standard THC units in screening and harm-reduction guidance rather than diagnostic decision-making.
Adolescents were found to be at a greater risk of CUD at lower levels of THC use than adults, supporting prevention-oriented guidance that emphasizes very low or no use during adolescence. Among adults, cannabis use exhibited a more distinct dose-response pattern, suggesting that quantity-based guidelines may offer important insights for cannabis harm reduction guidelines.
The longitudinal measurement of THC intake across products and methods is a key strength of this study, along with the use of clinical diagnoses rather than screening tools. However, the modest sample size, non-representative recruitment, and exclusion of clinical populations limit the generalizability of these findings. Furthermore, causal relationships could not be established, as higher THC use may both contribute to and result from CUD.
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