States with Legal Cannabis Saw More Asthma Hospitalizations

States with medical cannabis dispensaries experienced a 14.12% increase in inpatient asthma visits compared to states without. States with recreational cannabis legalization saw a 20.45% increase. These increases were primarily driven by Medicare and privately insured populations. Simple passage of medical cannabis laws or home cultivation allowances did not significantly affect asthma hospitalizations.

Difference-in-differences regression analysis using state-level quarterly inpatient visit data from the HCUP Fast Stats database (2005-2017). Compared asthma hospitalizations in 38 states before and after implementation of four types of cannabis laws, with analyses stratified by payer type.

While cannabis legalization debates focus on addiction and mental health, this study highlights an underappreciated respiratory consequence that carries substantial healthcare costs.

The finding that actual cannabis access (dispensaries, retail) drives asthma hospitalizations while law passage alone does not suggests the mechanism is increased cannabis smoke exposure rather than a legal status effect.

Ecological study cannot confirm individual-level cannabis use caused asthma hospitalizations. Other state-level changes may confound results. 2005-2017 timeframe precedes widespread vaping. Cannot distinguish between patient cannabis use and secondhand exposure.