Using a Field Performance Test on an iPad to Evaluate Driving Under the Influence of Cannabis
| Status: | Recruiting |
|---|---|
| Conditions: | Psychiatric |
| Therapuetic Areas: | Psychiatry / Psychology |
| Healthy: | No |
| Age Range: | 21 - 55 |
| Updated: | 5/5/2018 |
| Start Date: | January 2017 |
| End Date: | June 2019 |
| Contact: | Thomas Marcotte, PhD |
| Email: | tmarcotte@ucsd.edu |
A Randomized, Controlled Trial of Cannabis in Healthy Volunteers Evaluating Simulated Driving, Field Performance Tests and Cannabinoid Levels
This study was authorized by the California Legislature (Assembly Bill 266, the Medical
Marijuana Regulation and Safety Act (73) to help with detection of driving under the
influence of cannabis. One hundred and eighty healthy volunteers will inhale smoked cannabis
with either 0% (placebo), 5.9%, or 13.4% Δ9-THC at the beginning of the day, and then
complete driving simulations, iPad-based performance assessments, and bodily fluid draws
(e.g., blood, saliva, breath) before the cannabis smoking and a number of times over the
subsequent 6 hours after cannabis smoking. The purpose is to determine (1) the relationship
of the dose of Δ9-THC on driving performance and (2) the duration of driving impairment in
terms of hours from initial use, (3) if saliva or expired air can serve as a useful
substitute for blood sampling of Δ9-THC in judicial hearings and (4) if testing using an iPad
can serve as a useful adjunct to the standardized field sobriety test in identifying acute
impairment from cannabis.
Marijuana Regulation and Safety Act (73) to help with detection of driving under the
influence of cannabis. One hundred and eighty healthy volunteers will inhale smoked cannabis
with either 0% (placebo), 5.9%, or 13.4% Δ9-THC at the beginning of the day, and then
complete driving simulations, iPad-based performance assessments, and bodily fluid draws
(e.g., blood, saliva, breath) before the cannabis smoking and a number of times over the
subsequent 6 hours after cannabis smoking. The purpose is to determine (1) the relationship
of the dose of Δ9-THC on driving performance and (2) the duration of driving impairment in
terms of hours from initial use, (3) if saliva or expired air can serve as a useful
substitute for blood sampling of Δ9-THC in judicial hearings and (4) if testing using an iPad
can serve as a useful adjunct to the standardized field sobriety test in identifying acute
impairment from cannabis.
There are several studies that suggest higher doses of whole-blood Δ9-THC concentration are
associated with increased crash risk and crash culpability. However, attempts to define a
cut-off point for blood Δ9-THC levels have proven to be challenging. Unlike alcohol, for
which a level can be reasonably measured using a breathalyzer (and confirmed with a blood
test), detection of a cut-off point for intoxication related to Δ9-THC concentration has
eluded scientific verification. Recent evidence suggests blood Δ9-THC concentrations of 2-5
ng/mL are associated with substantial driving impairment, particularly in occasional smokers.
Others have countered that this level leads to false positives, particularly in heavy
cannabis users inasmuch as THC may be detectable in their blood specimens for 12-24 hours
after inhalation. Given that 12 to 24 hours is well beyond the likely period of driving
impairment, this would appear to be a justifiable objection to a per se cut-off point for a
Δ9-THC concentration indicative of impairment. Maximal driving impairment is found 20 to 40
minutes after smoking, and the risk of driving impairment decreases significantly after 2.5
hours, at least in those who smoke 18 mg Δ9-THC or less, the dose often used experimentally
to duplicate a single joint. Other studies, however, report residual MVA crash risk when
cannabis is used within 4 hours prior to driving.
The roadside examination using the Standardized Field Sobriety Test (SFST) for proof of
cannabis-related impairment has not been an ideal alternative to blood levels. Originally
devised to evaluate impairment under the influence of alcohol, the SFST is comprised of three
examinations administered in a standardized manner by law enforcement officers. The
'Horizontal Gaze Nystagmus' (HGN), the 'One Leg Stand' (OLS) and the 'Walk and Turn' test
(WAT) require a person to follow instructions and perform motor activities. During the
assessments, officers observe and record signs of impairment. In one study, Δ9-THC produced
impairments on overall SFST performance in only 50 % of the participants. In a separate study
involving acute administration of cannabis, only 30% of people failed the SFST. This
discrepancy in rate of failure was thought to be in part due to the participant's cannabis
use history. The reported frequency of cannabis use varied from once a week to once every 2-6
months in the study where there was a failure on the SFST by 50% of the participants. The
other study included more frequent users who smoked cannabis on at least four occasions per
week.
Based upon the above, another means is needed to help law enforcement officers discern
driving under the influence of cannabis. One future possibility is the development of
performance-based measures of cannabis-related impairments. This will include testing of
critical tracking, time estimation, balance and visual spatial memory learning. The
investigators have selected brief measures in order to be practicably administered repeatedly
over a short time period, as well as tests that have the potential to translate to a
tablet-based format, should there be benefit in possibly including these in future
performance-based measures for use in the field by law enforcement officers (e.g., a
cannabis-focused field sobriety test).
associated with increased crash risk and crash culpability. However, attempts to define a
cut-off point for blood Δ9-THC levels have proven to be challenging. Unlike alcohol, for
which a level can be reasonably measured using a breathalyzer (and confirmed with a blood
test), detection of a cut-off point for intoxication related to Δ9-THC concentration has
eluded scientific verification. Recent evidence suggests blood Δ9-THC concentrations of 2-5
ng/mL are associated with substantial driving impairment, particularly in occasional smokers.
Others have countered that this level leads to false positives, particularly in heavy
cannabis users inasmuch as THC may be detectable in their blood specimens for 12-24 hours
after inhalation. Given that 12 to 24 hours is well beyond the likely period of driving
impairment, this would appear to be a justifiable objection to a per se cut-off point for a
Δ9-THC concentration indicative of impairment. Maximal driving impairment is found 20 to 40
minutes after smoking, and the risk of driving impairment decreases significantly after 2.5
hours, at least in those who smoke 18 mg Δ9-THC or less, the dose often used experimentally
to duplicate a single joint. Other studies, however, report residual MVA crash risk when
cannabis is used within 4 hours prior to driving.
The roadside examination using the Standardized Field Sobriety Test (SFST) for proof of
cannabis-related impairment has not been an ideal alternative to blood levels. Originally
devised to evaluate impairment under the influence of alcohol, the SFST is comprised of three
examinations administered in a standardized manner by law enforcement officers. The
'Horizontal Gaze Nystagmus' (HGN), the 'One Leg Stand' (OLS) and the 'Walk and Turn' test
(WAT) require a person to follow instructions and perform motor activities. During the
assessments, officers observe and record signs of impairment. In one study, Δ9-THC produced
impairments on overall SFST performance in only 50 % of the participants. In a separate study
involving acute administration of cannabis, only 30% of people failed the SFST. This
discrepancy in rate of failure was thought to be in part due to the participant's cannabis
use history. The reported frequency of cannabis use varied from once a week to once every 2-6
months in the study where there was a failure on the SFST by 50% of the participants. The
other study included more frequent users who smoked cannabis on at least four occasions per
week.
Based upon the above, another means is needed to help law enforcement officers discern
driving under the influence of cannabis. One future possibility is the development of
performance-based measures of cannabis-related impairments. This will include testing of
critical tracking, time estimation, balance and visual spatial memory learning. The
investigators have selected brief measures in order to be practicably administered repeatedly
over a short time period, as well as tests that have the potential to translate to a
tablet-based format, should there be benefit in possibly including these in future
performance-based measures for use in the field by law enforcement officers (e.g., a
cannabis-focused field sobriety test).
Inclusion Criteria:
- Be a licensed driver.
- Need to have acuity of 20/40 or better, with or without correction on a Snellen Visual
Acuity eye chart.
Exclusion Criteria:
- At the discretion of the examining physician, individuals with significant
cardiovascular, hepatic or renal disease, uncontrolled hypertension, and chronic
pulmonary disease (eg, asthma, COPD) will be excluded.
- Unwillingness to abstain from cannabis for 2 days prior to screening and experimental
visits
- Positive pregnancy test
- A positive result on toxicity screening for cocaine, amphetamines, opiates, and
phencyclidine (PCP) will exclude individuals from participation.
- Unwilling to refrain from driving or operating heavy machinery for four hours after
consuming study medication.
We found this trial at
1
site
San Diego, California 92103
Principal Investigator: Thomas Marcotte, PhD
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