Transcript Presentation Title Goes Here

Impact of Changing Marijuana Laws
on Impaired Driving
Barry K Logan PhD, D-ABFT
Cannabis
• Most popular recreational drug in the US
after alcohol and tobacco.
• #1 Drug in the DUI Drug Arrests and 6.8%
of Friday and Saturday evening drivers test
positive for use.
• Some 25 million Americans have smoked
marijuana in the past year, and more than
14 million do so regularly.
• Possession and use illegal under federal
law, but states have variable policies on
enforcement and prosecution.
Cannabis and the Brain
Basal Ganglia
Cerebral Cortex
Movement
Higher cognitive function
Cerebellum
Movement
Hypothalamus
Appetite
Hippocampus
Medulla
Nausea/vomiting, CTZ
Creative Commons
Learning. Memory, stress
Spinal cord
Peripheral sensation/pain
Cannabis and Impairment
 Well known Cognitive effects include:
Concentration and sustained attention/vigilance.
Fatigue, sleepiness, lethargy, memory problems.
Reaction time
Difficulty in thinking and
problem-solving.
Difficulty in registering,
processing, and using
information.
Cannabis and Impairment
 Well Known Psychomotor Effects Include
 Decreased motor coordination
 Slurred speech
 Dizziness
 Impairment in reaction time
and tracking.
Cannabinoids and Driving
• Epidemiological Evidence
• Several studies support increased crash and
culpability risk resulting from driving within two hours of
smoking.
• More frequent cannabis exposure results in higher
odds ratios for MVA’s of ~2.5 (i.e. 2.5 X more likely).
• Fatally injured cannabis positive drivers (other drugs
may be present) had an adjusted OR of 8.6.
• Meta analysis of 16 published studies concluded an
adjusted OR of between 2.66 and 1.92, in cannabis
positive crash drivers.
Cannabinoids and Driving
• Experimental Evidence
• THC’s impairing effects increase with task complexity.
• Unexpected circumstances and choice during
otherwise monotonous driving exhibit increased risk
for errors over non cannabis using controls.
• Reaction time, road tracking, weaving, steering wheel
variability, and brake latency all increase with recent
cannabis exposure.
• THC effects on cognitive performance following
smoking include immediate recall, executive
functioning, working memory and attention.
Cannabinoids and Driving
• Experimental Evidence (cont’d.)
• Complex tasks involving multiple neurocognitive and
neuromotor skills are particularly sensitive to THC.
• Driving simulator studies support dose dependant
increases in weaving.
• Evidence of compensatory behavior in marijuana
impaired drivers.
• There is evidence of tolerance to some acute effects in
frequent users, however there is also evidence of long
term reversible impairment in baseline performance in
heavy chronic users following cessation.
Cannabinoids and Driving
• Experimental Evidence (cont’d.)
• Standardized Field Sobriety Tests are insensitive to
THC in some cases where there is objective evidence
of driving impairment.
• Cannabis use in conjunction with alcohol markedly
increases the level of impairment.
Hartman RL, Huestis MA. Cannabis effects on driving skills.
Clin Chem. 2013 Mar;59(3):478-92.
2007 Top Drugs in DUID Labs
Drug
Frequency
Cannabis
39
Benzodiazepines
37
Cocaine
37
Hydrocodone
30
Morphine/Codeine
28
Methamphetamine
26
Carisoprodol/Meprobamate
26
Oxycodone
16
Methadone
12
Antidepressants
11
Zolpidem
10
Number of
surveyed
Toxicology labs
listing cannabis
and other drugs in
their top 10
drugs.
Farrell et al, JFS, June 2007
Drugs in Arrested Drivers
• 92 DUI Drivers arrested in Miami, tested for alcohol and drugs.
• Alcohol-free impaired drivers: 72% positive for THC
• High BAC drivers: 22% positive for THC
Logan et al, JAT, June 2014
Drugs in Injured Drivers
• 108 Drivers admitted to a
level-1 trauma center.
• Tested in urine for major
drugs of abuse and impairing
therapeutics.
• 26.9% positive for THC
• 33% of alcohol drivers also
positive for THC
Walsh et al, Alc Anal Prev , 2005
2007 National Roadside Survey
Drug
THC
Cocaine
Hydrocodone
Oxycodone
Alprazolam
Methamphetamine
Sertraline
Propoxyphene
Tramadol
Diazepam
Amphetamine
Fluoxetine
Phentermine
Dextromethorphan
Methadone
Positivity
8.65%
3.92%
0.68%
0.82%
0.64%
0.84%
0.50%
0.52%
0.46%
0.38%
0.45%
0.37%
0.26%
0.22%
0.19%
Nightime Positivity – Blood
and Oral Fluid
 2.2% of randomly tested
drivers positive for alcohol
>0.08g/100mL
 16.3% positive for drugs
other than alcohol.
~80% of positives
accounted for by ~20% of
the drugs.
Cannabis use #1 at 8.65%
Drugs in Fatally Injured Drivers
• 397 fatally Injured Drivers State of WA, 2001-2002
• Tested in blood for major drugs of abuse and impairing
therapeutics.
• 12.7% positive for cannabinoids
• 17.3% of alcohol positive cases positive for cannabinoids
Schwilke et al, 2006
Changing US Attitudes to MJ
• November 2012
• WA State and CO legalize
possession by adults of 1oz of
useable MJ for recreational use.
• Regulate and tax sale and
distribution of marijuana.
• Focus enforcement on illegal
marijuana trade, and DUID
• November 2014
• OR, AK, and Washington D.C. follow suit
Marijuana DUI post Legalization
• Colorado
• The new law went into effect in January 2014.
• The THC percent positivity rates for January-February
data were 21%, 38%, 45% and 48% in 2011, 2012,
2013 and 2014, respectively.
• The positive rate appears to be steadily increasing and
the 2011-2012 increase was statistically significant.
• There was no significant difference between 2012 and
2013, 2012 and 2014 or 2013 and 2014 (Pearson's
chi-squared test at a=0.05).
S. Urfer, J. Morton, V. Beall, J. Feldmann, and J. Gunesch, “Analysis of Δ9tetrahydrocannabinol driving under the influence of drugs cases in Colorado from
January 2011 to February 2014,” J. Anal. Tox., vol. 38, no. 8, pp. 575–581, Oct. 2014.
Marijuana DUI post Legalization
• Washington
• The new law went into effect in January 2014*.
• The percentage of tested impaired driving cases which
were positive for Delta-9 THC in whole blood at
concentrations at or above 5 ng/mL were 18.6% and
24.9% in 2012 and 2013, respectively
• A significant increase (p=0.05) was noted between the
pooled prevalence, pre-legislation and the postlegislation of confirmed positive THC cases, implying
higher rates of use in the impaired driving population.
F. J. Couper and B. L. Peterson, “The prevalence of marijuana in suspected
impaired driving cases in Washington state,” J. Anal. Toxicol., vol. 38, no. 8, pp.
569–574, Oct. 2014.
NMS Labs DUID Marijuana Data
• 36,037 cases drawn from DUID arrests.
• 17,612 (48.8%) cases between Aug 2009
and Oct 2014 presumptively positive for
cannabinoids (ELISA, c/o 5ng/mL).
• 13,988 (79.4%) confirmed positive for one
of THC (1ng/mL), THC-COOH, (5ng/mL), or
THC-OH (5ng/mL).
• 7,448 cases were also screened for alcohol and other drugs:
benzodiazepines, opiates, cocaine metabolite, amphetamines, methadone,
phencyclidine, barbiturates, and propoxyphene.
• 6,877 cases had available gender, age, alcohol/other drug data:
• 80.6% male;
Mean/median age 29/25;
Range, 15-75
Demographics
Table 1. 7,448 Confirmed Cannabinoid Positive Cases with Alcohol
and Other Drug Data.
Other Drugs (+)
Other Drugs (-)
Total
Alcohol (+)
1,159 (15.6%)
3,178 (42.7%)
4,337 (58.2%)
Alcohol (-)
1,279 (17.1%)
1,832 (24.6%)
3,111 (41.8%)
Total
2,438 (32.7%)
5,010 (67.3%)
7,448 (100%)
Demographics
• Table 2. Rates of other drug and alcohol
positives within cannabinoid positive cases.
Drug Class
Alcohol
Cannabinoid cases
positive by other
drug class (%)
58.2%
Opiates
18.3%
Benzodiazepines
16.0%
Cocaine /Mets
8.49%
Amphetamines
6.42%
Methadone
3.42%
Phencyclidine
1.14%
Barbiturates
0.71%
Any Other Drug
32.7%
* p<0.05, difference in proportions test.
Concentrations
• Table 4. Percentage of cases that meet various per
se thresholds for DUID, based on a 1ng/mL c/o
+ Cannabinoid
+ Cannabinoid
+ Alcohol
+ Other Drug
+ Cannabinoid
+ Alcohol
- Other Drug
+ Cannabinoid
- Alcohol
+ Other Drug
+ Cannabinoid
- Alcohol
- Other Drug
>1 ng/mL THC
(Above per se
threshold in
PA)
>2ng/mL THC
(Above per se
threshold in
OH, NV)
>5ng/mL THC
(Above per se
threshold in
WA, CO, MT)
79.5%
60.3%
29.6%
71.9%
47.8%
19.0%
79.4%
56.8%
23.5%
74.6%
55.5%
28.6%
90.51%
78.9%
49.3%
Impact of 5ng/mL THC per se Law
10,144 Marijuana DUID /DRE cases testing positive for THC and/or metab.
25.00%
20.00%
15.00%
Relative Frequency %
10.00%
5.00%
0.00%
0
5
10
15
[THC]blood, ng/mL
Impact of 5ng/mL THC per se Law
10,144 Marijuana DUID /DRE cases testing positive for THC and/or metab.
25.00%
20.00%
15.00%
Relative Frequency %
10.00%
5.00%
0.00%
0
5
10
15
[THC]blood, ng/mL
Conclusions
• Cannabis use under typical conditions creates a highrisk of impairment for 2-4 hours after dosing.
• When used with alcohol, risk of impairment increases
substantially.
• Cannabis use is the drug category most frequently
detected in arrested, injured, and fatally injured drivers
after alcohol.
• There is no basis for setting a 5ng/mL per se standard
for THC at ~2 hours post-driving to reflect the level at
the time of driving.
Conclusions
• 81% of all cannabinoid drivers are below 5ng/mL at the
time of the test.
• 51% of drivers using only marijuana are below 5ng/mL
at the time of the test.
• 76.8% of cannabinoid positive drivers are also positive
for alcohol (60%), or other drugs (33%).
• Optimum solution is objective impairment assessment
using tools like the DRE program, with toxicological
confirmation of use at an analytically based cut-off of
1ng/mL.
Questions and Discussion
[email protected]