BACKGROUND AND AIMS: The impact of exposure to cannabis dispensaries on young adult cannabis use may depend on how exposures and outcomes are defined. We estimated associations of dispensary exposure with young adult cannabis use across: (a) a government-maintained licensed dispensaries registry versus a web-scraped list of licensed and unlicensed dispensaries; and (b) varying modes of cannabis modes (i.e. smoked, edible, vaped).

METHODS: This study used three waves of data (2021-2023) from a prospective cohort of n = 2277 young adults (mean baseline age = 22 years) from California, USA. Generalized linear models estimated the contemporaneous association of number of dispensaries within 1 mile of participants' homes with repeated measures of past 6-month, past 30-day frequency and past 30-day daily/near-daily (≥ 20 days/month) smoked, edible and vaped cannabis use (separate models for each product type). We compared associations for dispensary exposure derived from a government-maintained registry versus a validated web-scraped dispensary list.

RESULTS: For each additional dispensary located within 1 mile of home, young adults had 5-6% increased risk of past 6-month use of smoked, edible and vaped cannabis use using registry data and 3-4% increased risk using web-scraped dispensary data. Dispensary exposure was positively associated with past 30-day frequency of smoked [incidence rate ratio (IRR)(registry list) = 1.08, 95% confidence interval (CI) = 1.01-1.15; IRR(web-scraped) = 1.04, 95% CI = 1.00-1.08] and edible [IRR(registry list) = 1.07, 95% CI = 0.99-1.15; IRR(web-scraped) = 1.04, 95% CI = 0.99-1.08] cannabis use, but was not consistently associated with cannabis vaping frequency or daily/near-daily use of any product. Magnitude of associations was generally smaller when using dispensary data derived through web-scraping than the government-maintained registry of dispensary licenses, though conclusions were mostly similar between the two lists and confidence intervals consistently overlapped.

CONCLUSIONS: Living near a greater number of cannabis dispensaries within 1 mile of home appears to be associated with an increased risk of cannabis use. Web-scraped dispensary sources and United States government-maintained registry lists produce similar conclusions regarding the association of living near a greater number of dispensaries with young adult cannabis use.