1. Population Health and Optimal Health Practices Research Unit, CHU de Québec Research Center and Université Laval, Québec, QC, Canada; 2. Swiss Laboratory for Doping Analyses, University Center of Legal Medicine, Lausanne University Hospital, Lausanne, Switzerland; 3. Research Group on Adolescent Health, Institute of Social and Preventive Medicine, Lausanne University Hospital, Lausanne, Switzerland
Background: Young cannabis users are at increased risk for several mental health issues including dependence, depression and psychosis. THC-COOH (one of the two major metabolites from delta 9-tetrahydrocannabinol) is mostly used as a marker for both cannabis intoxication and abstinence when tested in urine. The present study assesses to which extent urine THC-COOH may help identify problematic cannabis users.
Methods: Data are issued from an observational study where, for methodological purposes, specific groups were recruited based on their tobacco and cannabis profile in the past month. Among a total of 269 participants, 57 cannabis-only users and 72 cannabis and tobacco users completed an anonymous self-administered questionnaire describing their cannabis use in the past month, most precisely in the past 5 days. The CAST (Cannabis Abuse Screening Test), a well validated questionnaire for both clinical and large epidemiological studies, was used to identify problematic cannabis use. Based on 6 items, participants scoring 2 and above were described as problematic cannabis users (PCU) in comparison to non-problematic cannabis users (NPCU). All participants also provided a urine sample that was blindly analyzed for THC-COOH among other substances, using gas-chromatography coupled mass-spectrometry. CPU and NCPU were compared on their cannabis use in the past month (at least once a week/less than once a week), consumptions in the past 5 days, and on urine THC-COOH levels (mean±SE). As a way to determine if urine THC-COOH is a proper marker to identify PCU, we used the receiver operating characteristic (ROC) curve to assess its sensitivity and specificity using various cut-off values.
Results: For the CPU group (81 participants, mean age 19 years, 64% male), smoking cannabis at least once a week (95% vs. 63%) was reported more frequently than among NCPU (48 participants, mean age 19 years, 63% male; p<0.001). Using ANOVAs, cannabis consumptions in the past 5 days (11.3±1.0 vs. 4.3±0.7; p=0.001) and urine THC-COOH levels (291.6±61.4 vs. 82.6±52.7; p=0.012) were higher among CPU than NCPU. With a cut-off of 23 ng/ml, positive urine THC-COOH has a sensitivity of 80% and a specificity of 54% for PCU. Using values above 120 ng/ml, the specificity increases to more than 95%.
Conclusion: Our study reveals that among regular cannabis users, urine THC-COOH levels are much higher among problematic cannabis users. Yet, urine THC-COOH mostly lack specificity towards problematic use at low levels. Users presenting with high value for THC-COOH on urine drug testing should be thoroughly screen regarding cannabis abuse and dependence diagnosis.
Sources of support: This study was funded by the Public Health Service of the Canton de Vaud. Dr Bélanger’s contribution was possible through grants from the Royal College of Physicians and Surgeons of Canada, the CHUQ/CMDP Foundation & the Laval University McLaughlin program, Québec, Canada.