Cannabis legalization and childhood asthma in the United States: An ecologic analysis.

Cannabis use is increasing among adults with children in the home particularly in states with cannabis legalization for medical (MCL) and/or recreational use (RCL), relative to states where cannabis use remains illegal at the state level. Exposure to secondhand smoke is a key risk factor for asthma among children. The objective of the current study was to investigate the relationship between MCL and RCL and the state-level prevalence of asthma among children in the United States (US). This ecological study used data from the 2011to 2019 National Survey on Children's Health, a representative sample of the population of minor children in the US. Changes in the annual prevalence of pediatric asthma by RCL/MCL over time were estimated using difference-in-difference (DID) analysis. Overall, a statistically significant decrease of 1.1% in the prevalence of pediatric asthma was observed from 2011- 2012 to 2018-2019. Adjusting for sociodemographic characteristics, overall reductions in asthma over time were generally greater in states in which cannabis use is fully illegal or with recent MCL adoption, but the rate of decline did not differ statistically by RCL/MCL status. Relative to 2011-2012 and to states where cannabis is fully illegal, the prevalence of asthma increased in states with RCL among youth 12-17 years old (2018-2019 DID = 2.56, p = .028) and among youth in some NH minoritized race/ethnicity groups (2016-2017 DID = 3.88, p = .013 and 2018-2019 DID = 4.45, p = .004). More research is needed to estimate the potential consequences of increased adult use of cannabis in the community for children's respiratory health.