Preliminary Outcomes from the Evaluation of Marijuana Legalization in Washington State: Youth and Adult Substance Use and Drug-Related Criminal Charges

In November 2012, Washington State voters passed Initiative 502 (I-502) which legalized limited adult possession and private use of cannabis.  The initiative authorized the state to regulate and tax the production and sale of cannabis and also added a new threshold for driving under the influence.  The initiative directs a percentage of cannabis tax revenues to prevention, treatment, and research, including a required benefit-cost evaluation of the law’s implementation over a 20-year period.  This presentation concerns the benefit-cost evaluation of I-502.  After providing brief introduction to legalization in Washington, our study requirements, and our research plan, the bulk of the presentation will focus on data describing the status of implementation of the law and preliminary results of outcome analyses.  Aspects of implementation that will be examined include development of the legal cannabis supply system as well as the prevention and treatment features of the law.  We will also report preliminary results from analyses of effects of the law on substance use and criminal justice outcomes, which represent an intermediate step towards the ultimate benefit-cost purpose of the study.    

Prevention and treatment activities supported by I-502 include evidence-supported programs and practices aimed at the prevention or reduction of youth substance abuse, and services for child and youth mental health and pregnant and parenting women.  Cannabis tax revenues also support a telephone helpline, local coordinated community-based planning capacity, media-based education campaigns, primary care services, poison control, and a website for public education.  Against the backdrop of implementation of the legal cannabis supply system and collection of tax revenues, we will describe the status of implementation of these public health features of the law over the same period of time. 

Then we will report preliminary results from outcome analyses examining the relationship between aspects of legal cannabis supply (e.g., sales volumes) at the county level, and trends in youth and adult use of cannabis, alcohol, and tobacco as measured in periodic surveys of the population of Washington.  We will also examine change in drug-related criminal charges in association with aspects of I-502 implementation including enactment of the law and growth in the legal supply of cannabis.  Pending the availability of data from the National Survey of Drug Use and Health we will also report results from analyses comparing adult substance use outcomes in Washington over the past decade to comparable measurements from other states over the same time period.  We will discuss the validity of a causal interpretation and implications for the benefit-cost analysis of the law.