The effects of cannabis liberalization laws on health, safety, and socioeconomic outcomes: An evidence and gap map

Cannabis is used annually by about four percent of the world’s population, with past-year global prevalence increasing nearly five percent over the last decade. Many countries and US states liberalized their cannabis laws over the past 25 years. The empirical literature examining the effects of cannabis laws and policies on use and other outcomes is interdisciplinary and diverse. New research appears regularly, with studies examining a wide range of health, safety, and socioeconomic outcomes. Yet, no concerted efforts have scoped this varied and growing literature.

This study presents an evidence and gap map (EGM) to fill current knowledge gaps by collecting and summarizing the available evidence. An EGM is a systematic review tool that provides a visual summary of strength of evidence and knowledge gaps within a particular policy domain. This EGM was developed and populated according to a conceptually-driven intervention-outcome framework, comprehensive literature search strategy, and dual data extraction and critical appraisal of studies.

We included 423 eligible studies in the EGM, published between 2004-2021. Most studies were from the USA and published since 2014. The majority focused on medical cannabis laws followed by recreational cannabis laws. Reported outcomes were diverse across domains. Most primary studies were of moderate study quality, followed by those of minimal quality. We documented ten systematic reviews in this policy space. Our results include presentation of an interactive, web-based EGM.

Despite a quarter-century of cannabis liberalization reforms across the globe, no EGM exists to summarize the available evidence and knowledge gaps in this policy space. Mapping this knowledge base summarizes the quality of evidence on cannabis liberalization reforms for decision-makers and identifies knowledge gaps for prioritizing new primary research and systematic reviews in this area.