The challenge of cannabis quantification: from theory to practice

Background: As cannabis becomes more available and socially accepted, it is increasingly important to facilitate research on this drug’s effects. A major hindrance, however, has been the lack of a standard unit by which to measure cannabis intake and compare its effects across studies. Existing experimental data are often hard to interpret due to the wide of consumption methods and cannabis products, as well as the variable concentration of cannabis compounds in such products, which limits the precision of measures such as ‘grams of cannabis’ or ‘number of joints smoked’. In an attempt to address this difficulty, a standard THC unit has been recently proposed, corresponding to a dose of 5 mg of THC. In the present work, our aim is to go from theory to practice, using the standard THC unit to quantify cannabis consumption in a group of patients in Portugal, unveiling the difficulties and limitations of this form of quantification.

Methods: This work was conducted in Centro Hospitalar de São João, in Porto, Portugal, and was based a group of patients included in study about cannabis-induced psychosis. Data on sociodemographic variables and cannabis consumption was collected at baseline through a self-administered questionnaire, with a professional available for clarification of doubts.

Results: At the time of preparation of this abstract, 14 participants had completed the questionnaire, 10 men and 4 women, aged between 20 and 50 years. The most used product was hashish and the most used method was joints. Participants indicated the number of joints smoked daily with ease, however some had difficulty indicating the wieght of hashish/herb consumed daily, with two participants not answering this question and alternatively indicating the average amount of money invested daily in the product. The others reported an average daily consumption of 0.73g of product, but were unaware of its THC potency, making quantification in THC units unfeasible. Assuming a THC potency between 15% and 30%, an average daily consumption of 22 to 44 THC units was estimated in our sample.

Conclusions: This pioneering work in quantifying cannabis consumption through the THC Unit allows us to expose the challenges of using this form of quantification. Here, the main difficulty was the participants’ unawareness of basic cannabis products information, such as the weight or THC potency, suggesting that such information was not available, is difficult to understand or cannabis users were not interest in it. A standard unit coupled with improved THC literacy among consumers would translate into better data quality, analysis and reporting, which in turn would improve researchers’ ability to communicate, educate and mitigate cannabis-related risks. Other limitations of the use of THC unit relate to the disregard of other cannabis components, namely cannabidiol content, that may influence the effects of THC, as well as the route of administration.