Kat Petrilli

Background and aims: Lower risk guidelines for safer levels of cannabis use could help to reduce the health burden posed by cannabis use disorder (CUD). We aimed to estimate risk thresholds for CUD based on delta‐9‐tetrahydrocannabinol (THC) consumption using standard THC units (1 unit = 5 mg THC). Design: Data from the CannTeen study, a longitudinal observational study consisting of five assessments over a 12‐month period. Setting: London, UK. Participants: Participants were n = 65 adults aged 26–29 (46% female, 70.77% white ethnicity) and n = 85 adolescents aged 16–17 (56% female, 65.48% white ethnicity). All participants reported at least one use of cannabis during the 12‐month study period. Measurements: Mean weekly standard THC units were estimated using the Enhanced Cannabis Timeline Followback, a comprehensive and validated assessment of quantity, frequency and potency of cannabis consumed. This was administered at 3‐month intervals and averaged over a 12‐month period. Past 12‐month diagnosis of CUD using The Diagnostic and Statistical Manual of Mental Disorders , Fifth Edition (DSM‐5) was assessed at the final follow‐up. Receiver operating characteristic curve models estimated 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 selected based on cut‐offs that maximised sensitivity and specificity. Findings: Discrimination accuracy of weekly standard THC units on CUD was good, with area under the curve > 0.70 for all models. Optimal cut‐offs for risk of any CUD (versus no CUD) were 8.26 units per week for adults and 6.04 units per week for adolescents. For risk of moderate/severe CUD (versus no CUD) optimal cut‐offs were 13.44 units per week for adults and 6.45 units per week for adolescents. Conclusions: Weekly cannabis consumption based on standard delta‐9‐tetrahydrocannabinol (THC) units appears to show good discrimination accuracy of cannabis use disorder at different severities and in different age groups. Safer levels of cannabis use, defined by low weekly standard THC unit consumption, could be recommended in lower risk cannabis use guidelines.

Aims: The aims of this study were to present an enhanced cannabis timeline followback (EC‐TLFB) enabling comprehensive assessment of cannabis use measures, including standard tetrahydrocannabinol (THC) units, and to validate these against objectively indexed urinary 11‐nor‐9‐carboxy‐tetrahydrocannabinol (THC‐COOH) concentrations.Design: We used cross‐sectional baseline data from the ‘CannTeen’ observational longitudinal study.Setting: The study was conducted in London, UK.Participants: A total of 147 participants who used cannabis regularly took part in the study (n = 71 female, n = 76 male; mean age = 21.90, standard deviation = 5.32).Measurements: The EC‐TLFB was used to calculate frequency of cannabis use, method of administration, including co‐administration with tobacco, amount of cannabis used (measured with unaided self‐report and also using pictorial aided self‐report) and type of cannabis product (flower, hash) which was used to estimate THC concentration (both from published data on THC concentration of products and analysis of cannabis samples donated by participants in this study). We calculated total weekly standard THC units (i.e. 5 mg THC for all cannabis products and methods of administration) using the EC‐TLFB. The outcome variable for validation of past week EC‐TLFB assessments was creatinine‐normalized carboxy‐tetrahydrocannabinol (THC‐COOH) in urine.Findings: All measures of cannabis exposure included in this analysis were positively correlated with levels of THC‐COOH in urine (r = 0.41–0.52). Standard THC units, calculated with average concentrations of THC in cannabis in the UK and unaided self‐report measures of amount of cannabis used in grams showed the strongest correlation with THC‐COOH in urine (r = 0.52, 95% bias‐corrected and accelerated = 0.26–0.70).Conclusions: The enhanced cannabis timeline followback (EC‐TLFB) can provide a valid assessment of a comprehensive set of cannabis use measures including standard tetrahydrocannabinol units as well as and traditional TLFB assessments (e.g. frequency of use and grams of cannabis use).

Background and Aims: Long‐term harms of cannabis may be exacerbated in adolescence, but little is known about the acute effects of cannabis in adolescents. We aimed to (i) compare the acute effects of cannabis in adolescent and adult cannabis users and (ii) determine if cannabidiol (CBD) acutely modulates the effects of delta‐9‐tetrahydocannabinol (THC).Design: Randomised, double‐blind, placebo‐controlled, crossover experiment. The experiment was registered on ClinicalTrials.gov (NCT04851392).Setting: Laboratory in London, United Kingdom.Participants: Twenty‐four adolescents (12 women, 16‐ to 17‐year‐olds) and 24 adults (12 women, 26‐ to 29‐year‐olds) who used cannabis 0.5–3 days/week and were matched on cannabis use frequency (mean = 1.5 days/week).Intervention: We administered three weight‐adjusted vaporised cannabis flower preparations: ‘THC’ (8 mg THC for 75 kg person); ‘THC + CBD’ (8 mg THC and 24 mg CBD for 75 kg person); and ‘PLA’ (matched placebo).Measurements: Primary outcomes were (i) subjective ‘feel drug effect’; (ii) verbal episodic memory (delayed prose recall); and (iii) psychotomimetic effect (Psychotomimetic States Inventory).Findings: Compared with ‘PLA’, ‘THC’ and ‘THC + CBD’ significantly (P < 0.001) increased ‘feel drug effect’ (mean difference [MD] = 6.3, 95% CI = 5.3–7.2; MD = 6.8, 95% CI = 6.0–7.7), impaired verbal episodic memory (MD = –2.7, 95% CI = −4.1 to −1.4; MD = −2.9, 95% CI = −4.1 to −1.7) and increased psychotomimetic effects (MD = 7.8, 95% CI = 2.8–12.7; MD = 10.8, 95% CI = 6.2–15.4). There was no evidence that adolescents differed from adults in their responses to cannabis (interaction P ≥ 0.4). Bayesian analyses supported equivalent effects of cannabis in adolescents and adults (Bayes factor [BF₀₁] >3). There was no evidence that CBD significantly modulated the acute effects of THC.Conclusions: Adolescent cannabis users are neither more resilient nor more vulnerable than adult cannabis users to the acute psychotomimetic, verbal memory‐impairing or subjective effects of cannabis. Furthermore, in adolescents and adults, vaporised cannabidiol does not mitigate the acute harms caused by delta‐9‐tetrahydocannabinol.

Background and objective Cannabis use during adolescence is common. Cannabis use and identity are thought to influence one another. This study aimed to examine what London-based adolescents (aged 16-17 years) think about cannabis use, its relationships with identity, and its benefits and harms. Method Three semi-structured focus groups interviews were conducted, two with adolescents who use cannabis (n=3 and n=5) and one with adolescents who do not use cannabis (n=6). Participants also completed a drug-use questionnaire. Results Thematic analysis (TA) revealed four identities. Two identities emerged from both groups: ‘The person who uses cannabis is chilled’ and ‘The person who uses cannabis is sometimes ostracised’. Two identities emerged from the group of adolescents who used cannabis: ‘The person who uses cannabis is an expert in risky things’ and ‘The person who uses cannabis is not addicted’. Skunk was identified as potentially more harmful than hash, but more powerful and pleasurable. Conclusion The findings provide insight into how cannabis use shape personal and social identity amongst teenagers in London in the late 2010s. Those who use cannabis described the benefits of cannabis, including socialising and for relaxation, and emphasised they are not addicted. Stigmatising and devaluing attitudes were held by some non-users about adolescents who use cannabis. Stereotypes seem to still exist, despite cannabis normalisation. Implications for research and policy are outlined.