Self-report methodology for quantifying standardized cannabis consumption in milligrams delta-9-tetrahydrocannabinol

ABSTRACT

Background: There is currently no format-independent method to determine delta-9-tetrahydrocannabinol (THC) in milligrams for self-report studies.

Objectives: Validate self-report method for quantifying mg THC from commercially available cannabis products using product labeling, which includes both net weight and product potency.

Methods: 53 adult cannabis users (24 M, 29F), 21–39 years of age (M = 28.38, SD = 4.15), were instructed to report daily use via a weekly survey for two consecutive weeks, provide product label photographs, abstain from use for 24 h, submit a urine sample and complete the Cannabis Use Disorder Identification Test – Revised (CUDIT-R) and the Marijuana Craving Questionnaire – Short Form (MCQ-SF). Milligrams of THC were determined by multiplying quantity of product used by its THC concentration. Urine was analyzed for the urine metabolite 11-nor-carboxy-THC (THC-COOH) via liquid chromatography mass spectroscopy. THC and THC-COOH values were log10 transformed prior to correlational analyses.

Results: Median daily THC consumption was 102.53 mg (M = 203.68, SD = 268.13). Thirty-three (62%) of the 53 participants reported using two or more formats over the 2-week period. There was a significant positive correlation between log10 THC-COOH and log10 THC mg (r(41) = .59, p < .001), log10 THC mg and MCQ-SF score (r(41) = .59, p < .001), and log10 THC mg dose and CUDIT-R score, (r(41) = .39, p = .010).

Conclusion: Our label-based methodology provides consumption information across all modalities of cannabis use in standard units that can be combined across products for calculation of dose. It is a viable and valid method for quantifying mg of THC consumed and can be utilized in any region where cannabis is legal, and labeling is regulated.

KEYWORDS:

• Marijuana
• dose
• self-report
• quantification
• bioavailability
• THC-COOH
• THC
• milligram

Acknowledgments

We acknowledge Valentina Apostol-Maughan for her help with designing the REDCap™ weekly diary and Josefin Koehn and the University of Washington Mass Spectrometry Center for THC metabolite analysis. In addition, we would like to thank the retail staff at cannabis dispensaries in the Seattle area for their insights on typical purchasing patterns, information on the variety of products available, and descriptions of the different ways newer formats are used. In particular, we would like to thank the staff at The Joint in Burien, WA for their support and willingness to share their expertise with our research staff.

Disclosure statement

The authors report no relevant disclosures.

Authorship contribution

Sarah Larsen: Conceptualization, Methodology, Software, Validation, Formal analysis, Data Curation, Writing – Original Draft, Visualization Allegra Johnson: Investigation, Project administration, Software, Validation, Writing – Review & Editing Mary Larimer: Writing – Review & Editing Stephen Dager: Writing – Review & Editing, Funding acquisition Natalia Kleinhans: Conceptualization, Funding acquisition, Formal analysis, Resources, Supervision, Writing – Review & Editing

Supplementary data

Supplemental data for this article can be accessed online at https://doi.org/10.1080/00952990.2023.2232525

Additional information

Funding

This work was supported by the National Institutes of Health / National Institute on Drug Abuse [R21DA046696] and by an internal grant from the University of Washington Department of Radiology