UC San Diego

Background and aims

Recreational cannabis has been legalized in 11 states and District of Columbia (DC) in the United States. Among these, 10 states further permitted retail sale to provide a legal supply to adults. This study examined the associations of cannabis exposures with recreational cannabis legalization and commercialization.

Design

Secondary data analysis of state-quarter level cannabis exposures during 2010-17 in the United States. Linear regressions with a difference-in-differences design were used to compare pre- and post-legalization trends in states that legalized recreational cannabis to contemporaneous trends in states that did not legalize recreational cannabis.

Setting

United States, including all 50 states and DC.

Cases

Cannabis exposures reported to the US National Poison Data System.

Measurements

The primary outcome was state age-adjusted cannabis exposures reported to the US National Poison Data System per 1 000 000 population per quarter. The two policy variables of interest included (1) the enactment of recreational cannabis legalization (i.e. removing penalties for adults' possession of cannabis in a small amount for recreational use) and (2) the initiation of recreational cannabis commercialization (i.e. providing a legal supply of cannabis to adults through licensed dispensaries).

Findings

The association between a state's enactment of recreational cannabis legalization and its changes in cannabis exposures was statistically non-significant overall. After controlling for recreational cannabis legalization, however, the initiation of recreational cannabis commercialization was associated with 5.06-5.80 more exposures per 1 000 000 population per quarter (67-77% increase relative to the pre-legalization average), depending on the composition of comparison states. The increase associated with commercialization was higher among minors than adults (7.97-9.53 versus 3.83-4.21 more exposures), higher among males than females (6.16-7.56 versus 3.76-3.91 more exposures) and higher among exposures with medical consequences than those without medical consequences (4.09-4.79 versus 0.97-1.01 more exposures).

Conclusion

An increase in cannabis exposures reported to the US National Poison Data System was observed following recreational cannabis commercialization in the United States.