Routes of Administration for Cannabis Use - Basic Prevalence and Related Health Outcomes: A Scoping Review and Synthesis

Background: Cannabis use is common, and associated with adverse health outcomes. 'Routes of administration' (ROAs) for cannabis use have increasingly diversified, in part influenced by developments towards legalization. This paper sought to review data on prevalence and health outcomes associated with different ROAs.

Methods: This scoping review followed a structured approach. Electronic searches for English-language peer-reviewed publications were conducted in primary databases (i.e., MEDLINE, EMBASE, PsycINFO, Google Scholar) based on pertinent keywords. Studies were included if they contained information on prevalence and/or health outcomes related to cannabis use ROAs. Relevant data were screened, extracted and narratively summarized under distinct ROA categories.

Results: Overall, there is a paucity of rigorous and high-quality data on health outcomes from cannabis ROAs, especially in direct and quantifiable comparison. Most data exist on smoking combusted cannabis, which is associated with various adverse respiratory system outcomes (e.g., bronchitis, lung function). Vaporizing natural cannabis and ingesting edibles appear to reduce respiratory system problems, but may come with other risks (e.g., delayed impairment, use 'normalization'). Vaporizing cannabis concentrates can result in distinct acute risks (e.g., excessive impairment, injuries). Other ROAs are uncommon and under-researched.

Conclusions: ROAs appear to distinctly influence health outcomes from cannabis use, yet systematic data for comparative assessments are largely lacking; these evidence gaps require filling. Especially in emerging legalization regimes, ROAs should be subject to evidence-based regulation towards improved public health outcomes. Concretely, vaporizers and edibles may offer potential for reduced health risks, especially concerning respiratory problems. Adequate cannabis product regulation (e.g., purity, labeling, THC-restrictions) is required to complement ROA-based effects.