Abstract
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).
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).
| Original language | English |
|---|---|
| Pages (from-to) | 772-783 |
| Number of pages | 12 |
| Journal | Addiction |
| Volume | 119 |
| Issue number | 4 |
| Early online date | 17 Dec 2023 |
| DOIs | |
| Publication status | Published - 17 Dec 2023 |
Funding
This work was supported by a grant from the Medical Research Council (MRC; award number MR/P012728/1) to H.V.C. and T.P.F. K.P. is supported by the Economic and Social Research Council (ESRC) as part of the South West Doctoral Training Partnership (SWDTP). L.A.H. is funded by the Wellcome Trust (grant ref: 209158/Z/17/Z). For the purpose of Open Access, the author has applied a CC by public copyright licence to any author‐accepted manuscript version arising from this submission. We would like to thank all the CannTeen participants for giving up their time to participate and everyone who contributed to the collection of the data.
| Funders | Funder number |
|---|---|
| The Wellcome Trust | 209158/Z/17/Z |
| Medical Research Council | MR/P012728/1 |
| Economic and Social Research Council |
Keywords
- Adult
- Female
- Humans
- Male
- Young Adult
- Cannabinoid Receptor Agonists
- Cannabis
- Cross-Sectional Studies
- Dronabinol
- Hallucinogens
- Longitudinal Studies
- Observational Studies as Topic