investigating changes in fatal- crash-involved drivers’ cannabinoid prevalence after passage of...
TRANSCRIPT
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Investigating Changes in Fatal-Crash-Involved Drivers’ Cannabinoid Prevalence after Passage of Medical Marijuana
Laws
G. Vanine Guenzburger Scott V. Masten
Research & Development
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Background• 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
• CA first to pass medical marijuana law in the US:
o Proposition 215 (1996) – Legalized o Senate Bill 420 (2004) – Operationalized
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US Medical Marijuana Laws
New Mexico
Maryland
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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?
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Data· Source: Fatality Analysis Reporting
System
· Outcome Measure: Prevalence % of drivers with detected
cannabinoids not necessarily impaired
· Regions studied: 13 states with Medical Marijuana laws
Cohorts: Two were studiedoAll drivers involved in fatal crashesoFatally-injured drivers
· Time Period: 1992 – 2009
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Confounding Variables
· Driver drug testing regularity in each state
oRelated to higher cannabinoid prevalence• Increased in CA after marijuana law
oVaries greatly from year to year
· National trend for drivers’ cannabinoid prevalence
oIncreased 1% to 4% in non-medical marijuana states from 1992-2009
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Drug testing and Cannabinoid Prevalence among CA Drivers in
fatal crashes
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
0
5
10
15
20
25
30
35
40
45
50
State Cannabinoid Prevalence State Drug Testing
YearPerc
en
tage o
f Fata
l-C
rash
-In
volv
ed D
rivers
Prop 215(1996)
SB 420(2004)
CA Testing increased
CA Marijuana prevalence did notdiffer from National Trend
Step change and plateau with operationalization
(2.1%)
National Trend approachingCalifornia’s
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All Fatal-Crash-Involved Drivers
State% step change in
prevalence
Access Rankings(most to
least)
California 2.1* 1
Michigan -0.1 2
Rhode Island -2.5 3
Maine 0.1 4
Montana -0.6 5
Colorado -0.2 6
New Mexico 0.1 7
Hawaii 6.0* 8
Washington 3.4* 9
Nevada 1.2 10
Oregon 0.1 11
Vermont 0.0 12
Alaska -2.2 13
Maryland 0.1 14
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Drug Testing and Cannabinoid Prevalence Killed CA Drivers
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
0
10
20
30
40
50
60
70
80
90
100 State Cannabinoid Prevalence State Drug Testing
Year
Perc
en
tage o
f Fata
lly-I
nju
red D
rivers
Prop 215(1996)
SB 420(2004)
CA Testingincreased
CA Marijuanaprevalencedid not differfrom National Trend
Step change and plateau withOperationalization
(5.7%)
National Trend Approaching California’s
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Fatally-Injured DriversState
% step change in prevalence
Access Rankings(most to least)
California 5.7* 1
Michigan 0.4 2
Rhode Island -4.6 3
Maine 0.0 4
Montana -1.4 5
Colorado -0.5 6
New Mexico 1.6 7
Hawaii 9.6* 8
Washington 4.6* 9
Nevada 2.0 10
Oregon -1.2* 11
Vermont -1.0 12
Alaska -1.5 13
Maryland 0.1 14
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Conclusions Implementation of medical marijuana laws was
associated with changes in cannabinoid prevalence among drivers involved in fatal crashes in only three stateso Californiao Hawaiio 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
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Recommendations
• Driver drug testing should be standardized and more consistent
• Next: Investigate relationship of driver marijuana use to crash contribution
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Questions / Follow-up
Contact:
Patrice Rogers, California DMV Research and Development Branch—DUI Unit [email protected]
G. Vanine GuenzburgerDMV Research and Development Branch—Project [email protected]
Research & Development Branch