The Role of Self‐Reported Willingness to Use Drugs in Public Health Research: Population‐Level Projections of Adolescents' Decriminalised Cannabis Use and Associated Risk Profiles

Introduction Public health planning in jurisdictions considering cannabis policy shifts may benefit from projections concerning post‐policy changes in cannabis use and user profiles. Multiple scenarios concerning decriminalised cannabis use among Norwegian high school students were projected using a simple but under‐utilised tool: their self‐reported willingness to do so. Methods A nationally representative sample of Norwegian high school students ( N = 3490) reported on their characteristics, cannabis use, and whether they would use cannabis if doing so were non‐punishable. These estimates were scaled up to census data and used to project the population sizes of students who may initiate/increase decriminalised cannabis use under various hypothetical willingness‐to‐behaviour transition scenarios. Multinomial regression models were used to identify risk profiles associated with willingness to use decriminalised cannabis. Results One in five participants (20.3%) reported lifetime cannabis use, corresponding to 38,200 student users nationally. Among never‐users, 8.0% reported willingness to initiate decriminalised cannabis use, while 22.3% were unsure. Among users, 40.3% reported willingness to increase decriminalised cannabis use, while 30.3% were unsure. Multiple projection scenarios indicated that both the prevalence (e.g., 12,000 new users nationally if all non‐users willing to initiate use would do so) and frequency of cannabis use (e.g., 15,400 more frequent users nationally if all users willing to increase use would do so) would increase under decriminalisation, especially among youth with certain socio‐demographic characteristics and recent histories of frequent use. Discussion and Conclusions Asking young people about their intended cannabis use under different policies provides an easily understandable and highly relevant tool in public health research and planning.