title: Changes in driver cannabinoid prevalence in 12 U.S. states after implementing medical marijuana laws.
abstract: OBJECTIVE
  To determine if cannabinoid prevalence increased among fatal-crash-involved drivers in 12 U.S. states after implementing medical marijuana laws.
  
  
  METHODS
  Time series analyses of 1992 to 2009 driver cannabinoid prevalence from the Fatality Analysis Reporting System.
  
  
  RESULTS
  Increased driver cannabinoid prevalence associated with implementing medical marijuana laws was detected in only three states: California, with a 2.1 percentage-point increase in the percentage of all fatal-crash-involved drivers who tested positive for cannabinoids (1.1% pre vs. 3.2% post) and a 5.7 percentage-point increase (1.8% vs. 7.5%) among fatally-injured drivers; Hawaii, with a 6.0 percentage-point increase (2.5 vs. 8.5) for all drivers and a 9.6 percentage-point increase (4.9% vs. 14.4%) among fatally-injured drivers; and Washington, with a 3.4 percentage-point increase (0.7% vs. 4.1%) for all drivers and a 4.6 percentage-point increase (1.1% vs. 5.7%) among fatally-injured drivers. Changes in prevalence were not associated with the ease of marijuana access afforded by the laws.
  
  
  CONCLUSIONS
  Increased prevalence of cannabinoids among drivers involved in fatal crashes was only detected in a minority of the states that implemented medical marijuana laws. The observed increases were one-time changes in the prevalence levels, rather than upward trends, suggesting that these laws may indeed provide marijuana access to a stable population of patients as intended, without increasing the numbers of new users over time. Although this study provides some insight into the potential impact of these laws on public safety, differences between states in drug testing practices and regularity, along with the fairly recent implementation of most medical marijuana laws, suggest that the long-term impact of these laws may not yet be known.
  
  
  CONCLUSIONS
  It is recommended that nationwide standardization of drug testing procedures and criteria be considered to improve the consistency of testing both between and within jurisdictions.
authors.affiliation: California Department of Motor Vehicles, Research and Development Branch, 2570 24th Street, MS H-126, Sacramento, CA 95818-2606, USA. Electronic address: Scott.Masten@dmv.ca.gov.
authors.forename: Scott V
authors.initials: SV
authors.lastname: Masten
authors.affiliation: California Department of Motor Vehicles, Research and Development Branch, 2570 24th Street, MS H-126, Sacramento, CA 95818-2606, USA.
authors.forename: Gloriam Vanine
authors.initials: GV
authors.lastname: Guenzburger
mesh_terms: D000063:Accidents, Traffic / Q000331:legislation & jurisprudence* / Q000401:mortality / Q000639:trends; D001334:Automobile Driving / Q000331:legislation & jurisprudence* / Q000706:statistics & numerical data; D002186:Cannabinoids / Q000009:adverse effects / Q000032:analysis*; D006801:Humans; D064086:Medical Marijuana / Q000009:adverse effects* / Q000627:therapeutic use; D015995:Prevalence; D015813:Substance Abuse Detection / Q000331:legislation & jurisprudence*; D014481:United States / Q000453:epidemiology
chemical_list: D002186:Cannabinoids; D064086:Medical Marijuana
keywords: Cannabinoids; Drugged driving; Medical marijuana laws; Prevalence; United States