High-Risk Cannabis Use: A Proposal of an Operational Definition through Delphi Methodology for Scientific Consensus.

Introduction: Cannabis ranks as one of the most widely used psychoactive substances worldwide. Its usage has been reported as a risk factor for developing a variety of physical and mental health issues, alongside social and economic problems. According to the World Health Organization (WHO), hazardous (or high-risk) substance use is defined as "a pattern of substance use that increases the risk of harmful consequences for the user." The primary objective of this study was to achieve a consensus on an operational definition of high-risk cannabis use suitable for a European jurisdiction (Spain).

Methods: A three round Delphi study was conducted. The Delphi technique entails group decision-making and iterative forecasting by consulting a panel of experts and conducting systematic feedback rounds. An online survey was distributed among a diverse expert panel comprising professionals from Spain working on fields related to cannabis use (research, policy planning, and clinical professionals). One-hundred ninety-nine invitations were sent to experts, of which forty-five (22.6%) accepted to participate. All participants were provided the option to revise a background document with the latest compiled scientific evidence and guidelines related to health and social conditions associated to cannabis usage. This background document also proposed the quantification of dose using a standardized unit established for the population of Spain (the Standard Joint Unit or SJU) based on quantity of cannabis main psychoactive constituent, 9-tetrahydrocannabinol (9-THC) (1 SJU = 1 joint = 0.25 g of cannabis = 7 mg of 9-THC). Three rounds of Likert scale and open-ended questions were administered until consensus, defined as ≥75% agreement, was attained.

Results: Consensus was reached on defining high-risk cannabis use as the usage of more than 4 SJU (>28 mg THC) per week or any use of cannabis with potency >10% THC. Concurrent use of cannabis with other drugs was also considered high risk, while the smoked route was considered the riskiest administration route. It was also agreed that vulnerable groups for high-risk cannabis use (for whom any pattern of cannabis use represents high risk of harm) include individuals under the age of 21, pregnant or breastfeeding women, individuals with psychiatric history, those with medical health issues related to cannabis use, professional drivers and heavy machine operators.

Conclusion: This operational definition of high-risk cannabis use for Spain elucidates usage patterns and individual vulnerability factors predictive of heightened harm. Its adoption holds potential to inform decision-making among individuals, professionals, and policy-makers, facilitating evidence-based interventions aimed at prevention and risk reduction.