Supporting Future Cannabis Policy – Developing a Standard Joint Unit : A Brief Back-Casting Exercise, Hugo López-Pelayo et al.

Supporting Future Cannabis Policy – Developing a Standard Joint Unit : A Brief Back-Casting Exercise.

Hugo López-Pelayo, Silvia Matrai, Mercè Balcells-Olivero, Eugènia Campeny, Fleur Braddick, Matthijs G. Bossong, Olga S. Cruz, Paolo Deluca, Geert Dom, Daniel Feingold, Tom P. Freeman, Pablo Guzman, Chandni Hindocha, Brian C. Kelly, Nienke Liebregts, Valentina Lorenzetti, Jakob Manthey, João Matias, Clara Oliveras, Maria Teresa Pons, Jürgen Rehm, Moritz Rosenkranz, Zoe Swithenbank, Luc van Deurse, Julian Vicente, Mike Vuolo, Marcin Wojnar and Antoni Gual

Frontiers in  Psychiatry, 2021, 12, 675033.

doi : 10.3389/fpsyt.2021.675033


The standardization of cannabis doses is a priority for research, policy-making, clinical and harm-reduction interventions and consumer security. Scientists have called for standard units of dosing for cannabis, similar to those used for alcohol. A Standard Joint Unit (SJU) would facilitate preventive and intervention models in ways similar to the Standard Drink (SD). Learning from the SD experiences allows researchers to tackle emerging barriers to the SJU by applying modern forecasting methods. During a workshop at the Lisbon Addictions Conference 2019, a back-casting foresight method was used to address challenges and achieve consensus in developing an SJU. Thirty-two professionals from 13 countries and 10 disciplines participated. Descriptive analysis of the workshop was carried out by the organizers and shared with the participants in order to suggest amendments. Several characteristics of the SJU were defined :

(1) core values: easy-to use, universal, focused on THC, accurate, and accessible;

(2) key challenges: sudden changes in patterns of use, heterogeneity of cannabis compounds as well as in administration routes, variations over time in THC concentrations, and of laws that regulate the legal status of recreational and medical cannabis use); and

(3) facilitators: previous experience with standardized measurements, funding opportunities, multi-stakeholder support, high prevalence of cannabis users, and widespread changes in legislation.

Participants also identified three initial steps for the implementation of a SJU by 2030:

(1) Building a task-force to develop a consensus-based SJU;

(2) Expanded available national-level data;

(3) Linking SJU consumption to the concept of “risky use,” based on evidence of harms.


Keywords : cannabis, standard units, harm-reduction, risky use, prevention



After tobacco and alcohol, cannabis is the most widely used psychoactive substance worldwide. Societies are experiencing a normalization of its use, especially among youth (1) as illustrated by the growing phenomena of coffeeshops and cannabis social clubs (2). Cannabis policy is shifting worldwide as the supply is moving from an unregulated (illicit) market to an open market for an “ordinary commodity” (e.g., in Canada, Uruguay and several states within the US). Observing that public opinion on the legal status of cannabis in Europe is also changing, European countries likely will not be an exception to this trend over the coming years. This changing context (i.e., in social perceptions and in legal context in some countries) aligns cannabis use in high-income countries more closely with alcohol or tobacco than to currently illegal drugs. A transition to legal, regulated access will require new prevention and harm-reduction strategies to minimize adverse effects as cannabis becomes more widely available (3). However, evidence also points to higher THC concentration in cannabis products during the last decade, which is believed to be associated with an increased risk of acute, and chronic health problems, especially in adolescents (4).

Additionally, the National Institute on Drug Abuse has already expressed plans to “explore the possibility of constructing a standardized dose similar to that for alcohol (the standard drink) and tobacco (a cigarette) [. . . for cannabis] for researchers to employ in analyzing use and [. . . ] for users to understand their consumption (5).” Learning from the history of measuring standard units, i.e., alcohol and tobacco, could facilitate public health, research and clinical professionals to navigate this new context more successfully and prevent errors from being repeated. During the 1980s and 1990s, several countries reached a national consensus defining their Standard Drink (SD) (6). Researchers conducted field tests in several countries to grow comparative evidence and adapt prevention efforts to the cultural characteristics of the country (7). However, most countries did not re-validate the SD with the field test (8). As a result, there are large differences between countries in defining SD, due to the fact that some are based on national consensus while others derive from experimental research, making useful cross- country comparison, policy analysis and prevention efforts more difficult. Nonetheless, despite its limited accuracy, the SD has advanced the alcohol public health field considerably: the SD provides clinicians, public health specialists, policy makers, and researchers with a common tool for assessing alcohol use and implementing programs from early identification of risky use (9) to monitoring consumption in harm-reduction (10).

Other relevant instruments for assessing alcohol use were based on the SD [AUDIT (11), ISCA (12), AUDIT-C (13), HRAR (14)] and are widely implemented globally. Screening and Brief Interventions (SBI) programs, make use of these instruments, are cost-effective in 24 out of 28 EU countries and cost-saving in 50% of countries (15). Learning from practical experiences in the alcohol field and the development and use of SD, the following should be essential characteristics in developing a Standard Joint Unit (SJU): (1) a high degree of evidence- based consensus on equivalence between countries; (2) high accuracy (providing a faithful representation of real doses); (3) taking into account less common routes of administration (cannabis is consumed in more varied ways than alcohol or tobacco); (4) built in monitoring of changes in patterns of use and chemical composition. Having said this, many peculiarities of cannabis use present challenges in the development of standard units for cannabis, among these are: different routes of administration (smoking, vaping, edible), concurrent use with other substances (e.g., tobacco, alcohol), heterogeneity of quantities or interactions among different cannabinoids (THC/CBD) (16). Standard units for cannabis, based on a fixed dose of THC, have the potential to address some of these challenges (16). What constitutes a SJU is important to consider. Currently, studies have gathered evidence on typical joints in Australia (140 mg cannabis/joint), Spain (250 mg of hashish or cannabis plant/joint and translating into 7 mg THC/joint), The Netherlands (260 mg cannabis/joint), UK (140 mg cannabis/joint and 380 mg cannabis/joint), USA (660 mg cannabis/joint vs. 580 mg cannabis/joint vs. 700 mg cannabis/joint) (17–24). Only the Spanish study reported milligrams of THC in a typical joint. Although a commendable start, these studies were heterogeneous regarding both methods (real/simulated cannabis, ecological/lab studies, etc. . . ) and results, even within countries. In the European Web Survey on Drugs (25), the EMCDDA also asks about usual amount consumed for herbal cannabis and cannabis resin. The rapid growth of research in this field also means that reaching a consensus on SJU research methodologies to support clinical implementation is an urgent issue. In order to advance this area, we organized a workshop, as part of the Lisbon Addictions Conference 2019, with experts in different disciplines (sociology, psychology, public health, basic and clinical research, psychiatry) and with the following objectives: (1) to reflect on the challenges to reaching a consensus on an operative SJU; (2) to reflect on opportunities and facilitators to achieving an SJU; (3) to propose different trajectories to achieve the main goal: implementation of a European SJU by the year 2030; and (4) to reach a minimum-level consensus on the first step toward achieving a SJU. The expected outputs were: (1) consensus on the first-steps toward achieving an SJU; and (2) a preliminary annual roadmap to develop a SJU by the year 2030.



The Back-Casting Exercise (BCE)

An operational definition of a BCE is “a scenario technique where normative targets or unwanted outcomes are defined by a group for the purpose of formulating ways in which such goals can be achieved or avoided” (26). Participants in back-casting exercises do not predict the future, but rather choose the desirable future and work backwards to define the steps to achieve that goal (26). Back-casting is a prospective method in the context of foresight methodologies. Foresight methodologies are “frameworks for making sense of data generated by structured processes to think about the future” (27). A back-casting exercise is useful when (28, 29):

  1. the problem is complex, persistent, and predominant.
  2. change is very necessary.
  3. sustainability of the solution is relevant.
  4. long-term planning (at least 5 years) is needed.
  5. the results of the exercise could impact multiple stakeholders and could empower the participants in the exercise.

The organizers pre-defined the desirable future in 2030 based on their professional expertise in the alcohol and cannabis areas (see Figure 1). The contrast between desirable future and current scenario (see below) is the starting point for the workshop discussions. The current scenario was defined as:

• The populations at risk of suffering cannabis-related health problems are not well-identified.
• The assessment of cannabis use patterns is usually based on frequency of use (e.g., days) only.

• A clear public health message about “how much is too much” does not exist because low-risk use is not well-defined.
• The prevalence of risky use (in different populations) is unknown due to lack of risk level definitions.

• Evidence-based practices to reduce cannabis-attributable harms (i.e., SBIRT) are not implemented.