Investigating Changes in Fatal- Crash-Involved Drivers’ Cannabinoid Prevalence after Passage of Medical Marijuana Laws G. Vanine Guenzburger Scott V. Masten 1

Background Marijuana use affects perception, concentration, decision making, attention, reaction time, and coordination Marijuana use affects perception, concentration, decision making, attention, reaction time, and coordination Marijuana use within 4 hrs. before driving associated with 2-6 times higher risk of crashing Marijuana use within 4 hrs. before driving associated with 2-6 times higher risk of crashing CA first to pass medical marijuana law in the US: CA first to pass medical marijuana law in the US: o Proposition 215 (1996) – Legalized o Senate Bill 420 (2004) – Operationalized 2

US Medical Marijuana Laws New Mexico Maryland 3

Research Questions 1.Are medical marijuana laws associated with changes in cannabinoid prevalence among drivers involved in fatal crashes in states with such laws? 2.Are changes in prevalence associated with the degree of patients’ accessibility to marijuana? 4

Data  Source: Fatality Analysis Reporting System  Outcome Measure: Prevalence  % of drivers with detected cannabinoids  not necessarily impaired Prevalence  % of drivers with detected cannabinoids  not necessarily impaired  Regions studied: 13 states with Medical Marijuana laws  Cohorts: Two were studied o All drivers involved in fatal crashes o Fatally-injured drivers  Time Period: 1992 –

Confounding Variables  Driver drug testing regularity in each state o Related to higher cannabinoid prevalence Increased in CA after marijuana law Increased in CA after marijuana law o Varies greatly from year to year  National trend for drivers’ cannabinoid prevalence o Increased 1% to 4% in non-medical marijuana states from

Drug testing and Cannabinoid Prevalence among CA Drivers in fatal crashes CA Testing increased CA Marijuana prevalence did not differ from National Trend Step change and plateau with operationalization(2.1%) National Trend approachingCalifornia’s 7

All Fatal-Crash-Involved Drivers State % step change in prevalence Access Rankings (most to least ) California 2.1* 2.1*1 Michigan Rhode Island Maine Montana Colorado New Mexico Hawaii 6.0* 6.0*8 Washington 3.4* 3.4*9 Nevada Oregon Vermont Alaska Maryland

Drug Testing and Cannabinoid Prevalence Killed CA Drivers CA Testing increased CA Marijuana prevalence did not differ from National Trend Step change and plateau with Operationalization(5.7%) National Trend Approaching California’s 9

Fatally-Injured Drivers State % step change in prevalence Access Rankings (most to least ) California 5.7* 5.7*1 Michigan Rhode Island Maine Montana Colorado New Mexico Hawaii 9.6* 9.6*8 Washington 4.6* 4.6*9 Nevada Oregon -1.2* -1.2* 11 Vermont 12 Alaska Maryland

Conclusions  Implementation of medical marijuana laws was associated with changes in cannabinoid prevalence among drivers involved in fatal crashes in only three states o California o Hawaii o Washington  Increases were step changes, not upward trends  Changes in prevalence were not associated with ease of patient access to marijuana Note: Volatility of driver drug testing may be masking law effects in the other states 11

Recommendations Driver drug testing should be standardized and more consistent Driver drug testing should be standardized and more consistent Next: Investigate relationship of driver marijuana use to crash contribution Next: Investigate relationship of driver marijuana use to crash contribution 12

Questions / Follow-up Contact: Patrice Rogers, California DMV Research and Development Branch—DUI Unit Manager G. Vanine Guenzburger DMV Research and Development Branch—Project Leader Research & Development Branch 13