Estimating thresholds for risk of cannabis use disorder using standard delta-9-THC units
An estimated 22 percent of cannabis users will develop cannabis use disorder, which causes clinically significant impairment or distress. Symptoms include an inordinate amount of time spent obtaining cannabis, using it, or recovering from its use; using cannabis for longer than intended; or the inability to meet work or school responsibilities because of cannabis use. Cannabis use is responsible for 35 percent of drug-treatment admissions in the European Union and is cited as a problem drug for 87 percent of those under 18 years old who are receiving drug treatment in the United Kingdom. The majority of people who have cannabis use disorder (CUD) do not seek professional treatment due to a preference for informal treatment options. Quantitative guidance on how people who use cannabis can reduce their risk of developing CUD is lacking. Risk factors for CUD include frequency of use and cannabis potency (% delta-9-tetrahydrocannabinol [THC]), with high potency being associated with an increased risk of negative outcomes. Established guidelines for safer levels of cannabis use could help reduce the health burden caused by CUD. The authors conducted a study to estimate risk thresholds for CUD based on THC consumption using standard THC units (one unit equals 5 mg of THC). The study used data from the CannTeen longitudinal observational study, which was conducted with participants from the greater London area and consisted of five assessments over a 12-month period. The study participants included 65 adults aged 26 to 29 years old (46 percent female; 70.77 percent white) and 85 adolescents aged 16 to 17 years old (56 percent female; 65.48 percent white). All participants reported at least one use of cannabis during the 12-month study period. The authors noted that cannabis is the most used illicit drug in the United Kingdom, with an estimated use of 6.8 percent in the adult population and 13.8 percent in the young adult population. The majority of users in the United Kingdom mix herbal cannabis with tobacco. The mean weekly standard THC units were estimated for the study using the Enhanced Cannabis Timeline Followback, a comprehensive and validated assessment of the quantity, frequency, and potency of cannabis consumed. The assessments were given at three-month intervals and averaged over a 12-month period. The diagnosis of CUD using The Diagnostic and Statistical Manual of Mental Disorders, fifth edition (DSM-5), was assessed at the final study follow-up. The authors used receiver operating characteristic curve models to estimate the extent to which weekly standard THC unit consumption could discriminate no CUD from any CUD (mild, moderate, or severe) and no CUD from moderate/severe CUD in adults and adolescents separately. Risk thresholds were derived based on cutoffs that maximized sensitivity and specificity. The findings showed that the discrimination accuracy of weekly standard THC units on CUD was good, with area under the curve greater than 0.70 for all models. The optimal cutoffs for risk of any CUD versus no CUD were 8.26 units per week for adults and 6.04 units per week for adolescents. In the risk of moderate/severe CUD versus no CUD category, the optimal cutoffs were 13.44 units per week for adults and 6.45 units per week for adolescents. The data indicated that weekly cannabis consumption based on standard THC units could discriminate CUD at different sensitivities for different age categories. The authors noted that the findings are broadly comparable to the cutoff of one standard joint unit per day for risk of moderate/severe CUD found in prior studies or approximately 10 standard THC units per week. The authors stated that they do not intend the thresholds from the study to be used as diagnostic criteria, but rather as a screening tool to indicate the probability that someone who uses cannabis has CUD.
Thorne RL, Lawn W, Petrilli K, et al. Estimating thresholds for risk of cannabis use disorder using standard delta-9-tetrahydrocannabinol (THC) units. Addiction. 2026. doi.org/10.1111/add.70263
Correspondence: Dr. Rachel Lees Thorne at [email protected]