Assessment of Driving Impairment from Cannabis

Transcription

1 Assessment of Driving Impairment from Cannabis Stephen Schmitz, PhD, MA Forensic Neuropsychologist Director, The Brain and Behavior Clinic - Denver and Boulder Clinical and Scientific Advisor, DriveABLE sps@bbcneuro.com

2 National Marijuana Laws 46 states have medical MJ laws Medical MJ laws vary 30 states and DC have laws in some form broadly legalizing MJ 8 states and DC have laws legalizing recreational MJ Federal law classifies MJ as a Schedule 1 drug (CSA) MJ dangerous, highly addictive, and having no medical value Inherent conflict between state and federal law

3 Colorado Legalization of Marijuana 1975 Marijuana decriminalized in Colorado November 2000 Amendment 20: First medical marijuana law November 2012 Amendment 64: Ended marijuana prohibition May 2013 DWDI 5ng/ml permissible inference standard but defense can argue not impaired January 2014 Full legalization statewide October 2017 Colorado ranked #1 in the nation for adult MJ use

4 Impact of Decriminalization of Marijuana on Driving Fatalities in Colorado MVA Fatality Driver positive for marijuana # of deaths MVA Fatality Marijuana related # of deaths MVA Fatality Driver positive for marijuana Percent of all traffic deaths (Pre-Legalization Era) (Legalization Era) 88 (66% increase) 2009 and prior 2016 and since 9% 21%

5 Prevalence of MJ Availability McDonald s 208 Starbucks 392 Marijuana Retail Stores 491

6 Marijuana and Driving Ability MJ most frequently detected drug (except ETOH) in crash-involved drivers Effect on CNS functions necessary for safe driving Memory Sustained Reaction and divided attention time Tracking Motor functioning Association not causation

7 Marijuana and Increased Crash Risk YES Systematic reviews and meta-analyses of epidemiological studies 2x increased risk of a motor vehicle collision Asbridge, 2012; Li, 2012; Hartman and Huestis, 2013 NO No increase in crash risk after adjusting for alcohol and demographics Romano, 2013; Elvik, 2013 DRUID study 9 European countries seriously injured and fatality crashes x increased risk NOT statistically significant

8 Drug and Alcohol Crash Risk: A Case-Control Study US Department of Transportation 2015 National Highway Traffic Safety Administration Case-control methodology 3000 crash-involved drivers 6000 control subjects selected for each crash driver 66% property damage only 33% injury crash 1% fatality crash Oral fluid or Blood draw

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10 Unadjusted and Adjusted Odds Ratios for Age, Gender, and Race Unadjusted odds ratio significantly associated with THC (1.25x) Adjusted odds ratio not significantly associated with THC (1.05x)

11 Current Colorado Marijuana Driving Law 5ng/ml permissible inference Driver can argue not impaired while driving Too low or too high? Too low Heavy effects users develop tolerance for impairing No scientific basis for a 5ng/ml THC legal limit impairing driving ability Too high Any MJ impairs cognitive functioning Essentially No establishes a license to drive stoned scientific basis for a 5ng/ml THC legal limit impairing driving ability

12 Meta-analysis of cognitive effects of smoked cannabis, comparing dose, plasma THC levels, and test performance Following a single THC exposure to occasional users, a whole blood THC of 1.9 ng/ml corresponded to a blood alcohol concentration of 0.05%* After 4.75 hours <15% of the tests results were impaired, a performance found at BAC < 0.03% * Based on 888 neuropsychological effects reported in 78 studies employing THC doses of 1-52 mg in occasional users. The range of blood THC associated with ± 10% variation in this level of impairment was 1.7 to 2.3 ng/ml. [Berghaus, G, Sticht G, Grellner W et al. Meta-analysis of empirical studies concerning the effects of medicines and illegal drugs including pharmacokinetics on safe driving." Bergisch Gladbach: BASt2010. Report No.: D 1 (2011)]

13 Neurocognitive performance during acute THC intoxication in heavy and occasional cannabis users [Ramaekers J et al. J Psychopharm 23: ; 2009] 12 occasional cannabis users and 12 heavy users participated in double-blind, placebo-controlled, 2-way balanced trial. Endpoints included critical tracking task, and divided attention tasks Paced smoking of placebo or joint (13% THC) delivering 500 μg/kg dose in 10 minutes ( 25 hits) Whole blood THC 15 min after smoking: 23.7 ± 14.1 ng/ml (heavy users); 10.4 ± 4.6 ng/ml (occ users) Heavy users were tolerant to impaired performance after THC Occ. users + THC Occ. users + THC critical tracking test (standardized score) divided attention task Occ. users + THC

14 Psychomotor and neurocognitive effects in occasional and frequent smokers Both groups feel high [Desrosiers N et al. J Anal Toxicol 39: ; 2015] Frequent users tolerant to slowed reaction time

15 Neurophysiological and cognitive effects of smoked marijuana in frequent users [Hart C et al. Pharmacol Biochem Behav 96: ; 2010]

16 Hart et al, 2011

17 In an on-the-road driving test, oral dronabinol (THC 20 mg) significantly impaired road tracking (SDLP) and car following performance in occasional but not heavy cannabis users dotted line equates to BAC 0.05% Blood THC at 1.5 hr post 20 mg 5.1 ± 1.1 ng/ml (heavy users) 3.1 ± 0.7 ng/ml (occ. users) Bosker W et al. Addiction 107: ; 2012

18 Blood THC Levels Decline Rapidly

19 Tolerance in Chronic Users Days of supervised abstinence (subject L) Karschner et al. Jour Annal Toxicol. 33: , 2009

20 Observational Study of Driving Impairment in Occasional Versus Heavy Marijuana Users Co-PI s: Michael Kosnett & Ashley Brooks-Russell - CU Anschutz Co-investigators: Tim Brown & Gary Milavetz - U of Iowa Chris Halsor, Dave Carbonetti - Understanding Legal Marijuana Greg Dooley CSU Stephen Schmitz - DriveABLE and Private Practice Sam Wang, CU Anschutz Becki Bartelson,Victoria Anderson, AR Olson, Kyle Friedman - Denver Health

21 Primary Aim Compare driving impairment in occasional vs. heavy marijuana users, before and after smoked marijuana Driving simulator Standardized ipad-based Field Sobriety Test neurocognitive test battery

22 Secondary Aims Calculate the sensitivity, specificity and predictive value of the ipad CARE test battery for validated benchmarks of driving impairment measured in the MiniSim. Determine if blood cannabinoid profiles predict driving impairment differentially in occasional and heavy (i.e. daily) marijuana users as measured on the three driving assessment tools. Evaluate the predictive value of a blood THC concentration of 5 ng/ml (and other blood THC cut-points, including various metabolite ratios) for driving impairment in occasional marijuana users and in heavy marijuana users.

23 Pre-Post Change Analysis 3 groups 30 ss each Occasional users MJ use 1 day/week and 2 days/week (last 30 days) Heavy users daily (last 30 days) Non-users No MJ use (last 30 days) 2 times/month (last 90 days) Baseline assessments (after overnight abstinence) Smoking session Post assessments

24 Methods Pre-screening Inclusion/exclusion criteria Screening visit Urine Breathalyzer Driving 7 simulator minutes Simulator Visual adaptation syndrome acuity Study diary MJ 2 use, medications, alcohol, sleep duration days before first study visit

25 National Advanced Driving Simulator MiniSim

26 Simulated Scenarios Highway and city driving environments Collision situation Following Lane position Distractor Each subject will undergo 2 sessions Duration 30 minutes

27 Braking Lead Vehicle Braking While the driver is distracted, the lead vehicle which is 3.5seconds ahead brakes to 20 mph at a high level of deceleration (0.85g) (~2.25s), and then maintains 20 mph for 5 seconds. Oncoming traffic prevents passing. Braking Lead Vehicle Stopped While the driver is distracted, the lead vehicle which is 4 seconds ahead brakes to a stop at very high level of deceleration (2g) Steering Curve Departure Driver going around a tightening radius curve at too great a speed (missing reduced speed sign) requiring a steering response Steering Slick Road Departure opposed to aggressive driving. Steering Avoidance Departure - right incursion hidden driveway requiring steering response Steering Wind Gust Driver traveling on two-lane roadway. Wind gust from the left pushes the driver requiring a steering response for recovery. Steering Obstacle Avoidance driver to make steering response Steering Left Incursion Driver traveling on a two-lane roadway. Oncoming vehicle crosses into driver's lane requiring a steering resposne. Braking Lead Vehicle Braking Traveling on a two-lane roadway, while driver is distracted, vehicle slows to turn onto interstate causing lead vehicle to brake Varied Red Light Runner runs the red light Varied Left Turn Across Path Driver approaches intersection to turn left. Oncoming traffic is hidden. As driver accelerates oncoming traffic enters the intersection Braking Lead Vehicle Revealed Following a vehicle at 40 mph with a time headway of 2.25 seconds, the lead vehicle changes lanes while the driver is engaged in a distraction task revealing a stopped lead vehicle. Similar to Curve Departure but simulates loss of control due to weather conditions as Driver traveling on a two-lane roadway. Vehicle enters roadway from Driver traveling on a multilane roadway. Desk falls out of the back of truck requiring Driver approaches signalized intersection with the green light. Hidden vehicle from the left

28 MiniSim - Limitations Not highly correlated with actual driving More relaxed and less controlled in a simulator Sd larger Simulator adaptation syndrome

29 Standardized Field Sobriety Test SFST Horizontal Gaze Nystagmus Visually focus on object moved horizontally and vertically Walk and Turn 9 heel-to-toe steps forward and back along straight line One Leg Stand Stand on one leg with other leg stretched out in front of them Count out loud for 30 seconds Sensitive test related to BAC Sensitive-ish to marijuana

30 Sensitivity of SFST to Detect Impairment Due to Marijuana Intoxication 40 Ss Occasional users Placebo or marijuana Low dose % THC High dose 2.93% THC One cigarette fully consumed Blood sample Prior, immediately after smoking, and every 20 min for 2 hrs SFST 5 min after smoking, 55 min, 105 min Papafotiou et al. PsyPharm, 2005, 180,

31 SFST and Marijuana 5 minutes 55 minutes 105 minutes

32 Impairment on SFST in Low (1.8%) vs High (3.0%) THC Content Levels Stough, et al. 2006, NDLERF

33 DriveABLE Ipad - Cognitive Ability Real-Time Evaluation (CARE) Originally developed driving assessment tools for dementia/tbi On-Road PC evaluation based evaluation Over 100,000 evaluations Predictive values >.88 Roadside assessment tool in development - CARE Ipad based Measure of real-time cognitive abilities correlated with driving 5-10 minute administration

34 Cognitive Ability Real-Time Evaluation (CARE) Evidence based Correlates Purposely Quick to actual behind the wheel driving risk focused on ease of use to administer Legally defensible in court

35 Cognitive Ability Real-Time Evaluation (CARE) DriveABLE Cognitive Assessment Tool Cognitive Ability Real-Time Evaluation Task 1: Motor Speed & Control Task 2: Span of Attentional Field Task 1: Reactions Task 3: Spatial Judgement & Decision Task 2: Judgement Task 4: Attentional Shifting Task 5: Memory & Exective Function Task 6: Identification of Driving Situations Task 4: Memory Function Task 4: Control

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37 Challenges Observational study (IRB) University legal concerns Finding off-campus space Timeline Begin recruitment: early 2018 Initiate Share study: early 2018 mid 2019 findings: late 2019 early 2020

38 Summary of Key Points Use of THC can result in acute CNS effects that may impact cognitive performance and driving in some users for several hours Tolerance to CNS effects that mitigates impairment may develop in chronic frequent users Blood tests that measure THC and other cannabinoids in blood may correlate with impairment in some users (moreso occasional users than chronic users) Additional research is needed regarding the temporal pattern of pharmacokinetic and pharmacodynamic effects, including the utility and predictive value of roadside measurements