Prevalence of cannabis use in youths after legalization in Washington state

By Julia A Dilley, Susan M Richardson, Beau Kilmer, Rosalie Liccardo Pacula, Mary B Segawa, Magdalena Cerdá

Methods| The Washington Healthy Youth Survey (HYS) 2 is an anonymous, school-based survey of 8th, 10th, and 12th graders and the state’s primary source of information about health behavior among youths. The HYS has been implemented in the fall of even-numbered years since 2002, using a simple random sample of public schools to generate a state-representative sample. Response rates (incorporating school and student response) in 2016 were 80% for 8th grade, 69% for 10th grade, and 49% for 12th grade. The study was approved by the Washington State Institutional Review Board, whose general policy waives informed patient consent when data are de-identified. We Generated Covariate-adjusted prevalence estimates, modeling as closely as possible to Cerdá et al. Prevalence was based on modeled estimates (ie, SUDAAN predMARG [RTI International] postestimation command). Because the the MTF is not designed to provide state-representative estimates, the article generated covariate-adjusted modeled prevalence estimates for each state. The article suggested complex association between legalization and cannabis use among youths: increases in prevalence among Washington 8th and 10th graders, but not among 12th graders, relative to use in states without legalization of recreational marijuana.

The authors noted that, “the sample design may lead to discrepancies between MTF results and those found in other large-scale surveillance efforts.”1(p148) The purpose of the present study was to assess whether trends in cannabis use prevalence among youths from Washington’s state-based youth survey are consistent with findings from the MTF.

JAMA pediatrics, 173(2) 2019