Cannabis Intoxication
Conditions
Keywords
Driving Under the Influence, Memory Impairment, Reaction Time, Time Perception, Cannabis, Marijuana, Whole Blood, Oral Fluid, Breath, Driving simulator
Brief summary
This study was authorized by the California Legislature (Assembly Bill 266, the Medical Marijuana Regulation and Safety Act 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-tetrahydrocannabinol (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, 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.
Detailed description
There are several studies that suggest higher doses of whole-blood Δ9-tetrahydrocannabinol (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 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 over the following 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 motor vehicle accident 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 50 % of the participants. In a separate study involving acute administration of cannabis, 30% of people failed the SFST. This discrepancy was thought to be in part due to the participant's cannabis use history, as well as low percentage of THC in the cannabis. 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 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 field-feasible 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).
Interventions
DRUGCannabis
Participants will smoke a cannabis cigarette ad libitum as per their usual routine
Sponsors
University of California, San Diego
Study design
Allocation
RANDOMIZED
Intervention model
PARALLEL
Primary purpose
SCREENING
Masking
TRIPLE (Subject, Investigator, Outcomes Assessor)
Masking description
Product will be dispensed from the Research Pharmacy. All assessors, investigators, and participants are blinded to the THC content.
Intervention model description
Participants will be randomized to smoke a cannabis cigarette containing placebo (.02%), 5.9% or 13.4% THC.
Eligibility
Sex/Gender
ALL
Age
21 Years to 55 Years
Healthy volunteers
Yes
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.
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Change in Composite Drive Score (CDS) From Pre-smoking Simulation | Participants are assessed pre-smoking, and then approximately 30m, 1h 30m, 3h 30m and 4h 30m post-smoking | The Composite Drive Score (CDS) is a z-score comprised of key variables from the simulator tasks (SDLP, speed deviation, and task accuracy during the modified Surrogate Reference Task (mSuRT); coherence from the car following task). This outcome reflects the change in CDS from the pre-smoking assessment, at each timepoint. The z-score indicates the number of standard deviations away from the mean from the baseline performance for the entire group (n = 191). A Z-score of 0 is equal to the mean of a reference population (in this case the pre-smoking performance for the entire group). Higher z-scores at each timepoint indicate worse performance (variables that went in the opposite direction were reflected in order to have all variables have the same direction). When examining the change in Composite Drive Score (this outcome variable), a higher score indicates a decline in performance (e.g., Time 2 minus Time 1). |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Simulator: Speed Deviation | Participants are assessed pre-smoking, and then approximately 30m, 1h 30m, 3h 30m and 4h 30m post-smoking | The variability in speed during the modified Surrogate Reference Test (mSuRT). The speed is in miles per hour. Range is from .17 to 12.85. A higher score indicates worse performance. |
| Simulator: Correct Hits on mSuRT | Participants are assessed pre-smoking, and then approximately 30m, 1h 30m, 3h 30m and 4h 30m post-smoking | The number of times the participant touched the correct stimulus (circle) on the iPad, during modified Surrogate Reference Task (mSuRT). Range is from 8 to 32. A higher score is a better score. |
| Simulator: Car Following - Coherence | Participants are assessed pre-smoking, and then approximately 30m, 1h 30m, 3h 30m and 4h 30m post-smoking | Coherence is the correlation (0 to 1) between the participant and the lead car (which speeds up and slows down), representing the participant's ability to accurately speed up and slow down similarly to the lead car. Range of scores is from .01 to .97. A higher score is a better score. |
| Simulator: Response Delay - Car Following | Participants are assessed pre-smoking, and then approximately 30m, 1h 30m, 3h 30m and 4h 30m post-smoking | Time delay (in seconds) in responding to changes in the lead car's speed. Range is from -5.8 to 6.0. A higher score indicates a worse score. |
| Simulator: Distance From Lead Car - Car Following | Participants are assessed pre-smoking, and then approximately 30m, 1h 30m, 3h 30m and 4h 30m post-smoking | The outcome is distance from the lead car (in virtual feet) during the Car Following Task |
| Tablet Assessment: Dual Attention Missed Switches | Participants assessed pre-smoking and 1 hour, 2 hours, 4 hours, and 5 hours after smoking | The participant follows a moving target (square) with her/his finger, and switches to following a new stimulus when it appears in the corner of the screen. Each participant was classified as to whether he/she missed any of these switches during the trial. The outcome is the proportion of participants within each group who missed at least one switch. The range is from 0 to 1. Higher indicates a worse score. |
| Simulator: Standard Deviation of Lateral Position (SDLP) | Participants are assessed pre-smoking, and then approximately 30m, 1h 30m, 3h 30m and 4h 30m post-smoking | This measures the standard deviation of lateral (lane) position, or the degree to which the participant swerves within the road lane on the driving simulation during the modified Surrogate Reference Task (mSuRT). The range is from .39 to 3.33. A higher score indicates worse performance. |
| Tablet Assessment: Visual Spatial Learning Test Number Correct | Participants assessed pre-smoking and 1 hour, 2 hours, 4 hours, and 5 hours after smoking | Assessment of short-term memory for abstract figures. The participant is to memorize abstract figures and their locations on a 3 x 3 grid. After initial viewing (10 seconds), the figures go away for either 4, 12, or 24 seconds. The participant is then to identify which figures were in the initial viewing (from a list at the bottom of the screen), and place them at the correct location. This is the number of correctly identified figures. The range is from 0 to 12. A higher score indicates better performance. |
| Tablet Assessment: Time Estimation | Participants assessed pre-smoking and 1 hour, 2 hours, 4 hours, and 5 hours after smoking | The participant is to estimate the amount of time that has passed while performing a secondary task. This outcome is the ratio of 1) the estimated time that has passed (seconds), divided by 2) the actual amount of time that has passed. The range is from 0.204 to 1.89. A higher score indicates a better performance. |
| Tablet Assessment: Balance | Participants assessed pre-smoking and 1 hour, 2 hours, 4 hours, and 5 hours after smoking | While standing and keeping their feet still, this is a measure of the participant's sway, which is the total distance that the participant's body moved (in meters) from his/her initial vertical position. This was measured using an accelerometer placed on the participant's back. The range of scores is from .222 to 1.661. A higher score indicates worse performance. |
| THC Concentrations: Correlation Between Blood and Oral Fluid | Approximately 15 minutes post-smoking | Spearman's correlation between THC concentrations in whole blood and oral fluid. Higher scores are better. |
| THC Concentrations: Correlation Between Whole Blood and Breath | Approximately 15 minutes post-smoking | Spearman's correlation between THC concentrations in whole blood and breath |
| Tablet Assessment: Lane Tracking Standard Deviation | Participants assessed pre-smoking and 1 hour, 2 hours, 4 hours, and 5 hours after smoking | The participant is to rotate the iPad in order to keep a round object in the center, between two lines (lanes). This measure is the standard deviation of the position of the round object during the task (in essence, how much swerving there is within the lane). The range is from 8.2 to 189.4. A higher score indicates worse performance. |
Countries
United States
Participant flow
Participants by arm
| Arm | Count |
|---|---|
| Placebo Cannabis with .02% THC | 63 |
| 5.9% THC Cannabis with 5.9% THC | 66 |
| 13.4% THC Cannabis with 13.4% THC | 62 |
| Total | 191 |
Withdrawals & dropouts
| Period | Reason | FG000 | FG001 | FG002 |
|---|---|---|---|---|
| Overall Study | Oral THC > 5ng/mL prior to treatment (indicating likely recent use) | 2 | 3 | 2 |
| Overall Study | Withdrawal by Subject | 0 | 1 | 0 |
Baseline characteristics
| Characteristic | Placebo | 5.9% THC | 13.4% THC | Total |
|---|---|---|---|---|
| Age, Continuous | 28.1 years STANDARD_DEVIATION 7.3 | 30.7 years STANDARD_DEVIATION 8.8 | 30.9 years STANDARD_DEVIATION 8.6 | 29.9 years STANDARD_DEVIATION 8.3 |
| Race/Ethnicity, Customized African American | 8 Participants | 6 Participants | 4 Participants | 18 Participants |
| Race/Ethnicity, Customized Asian | 5 Participants | 8 Participants | 4 Participants | 17 Participants |
| Race/Ethnicity, Customized Hispanic | 15 Participants | 19 Participants | 22 Participants | 56 Participants |
| Race/Ethnicity, Customized Indigenous | 5 Participants | 2 Participants | 1 Participants | 8 Participants |
| Race/Ethnicity, Customized Multiracial | 2 Participants | 3 Participants | 2 Participants | 7 Participants |
| Race/Ethnicity, Customized Non-Hispanic White | 28 Participants | 28 Participants | 27 Participants | 83 Participants |
| Race/Ethnicity, Customized Unknown | 0 Participants | 0 Participants | 2 Participants | 2 Participants |
| Region of Enrollment United States | 63 participants | 66 participants | 62 participants | 191 participants |
| Sex: Female, Male Female | 31 Participants | 19 Participants | 23 Participants | 73 Participants |
| Sex: Female, Male Male | 32 Participants | 47 Participants | 39 Participants | 118 Participants |
Adverse events
| Event type | EG000 affected / at risk | EG001 affected / at risk | EG002 affected / at risk |
|---|---|---|---|
| deaths Total, all-cause mortality | 0 / 65 | 0 / 70 | 0 / 64 |
| other Total, other adverse events | 2 / 65 | 15 / 70 | 5 / 64 |
| serious Total, serious adverse events | 0 / 65 | 0 / 70 | 0 / 64 |
Outcome results
Primary
Change in Composite Drive Score (CDS) From Pre-smoking Simulation
The Composite Drive Score (CDS) is a z-score comprised of key variables from the simulator tasks (SDLP, speed deviation, and task accuracy during the modified Surrogate Reference Task (mSuRT); coherence from the car following task). This outcome reflects the change in CDS from the pre-smoking assessment, at each timepoint. The z-score indicates the number of standard deviations away from the mean from the baseline performance for the entire group (n = 191). A Z-score of 0 is equal to the mean of a reference population (in this case the pre-smoking performance for the entire group). Higher z-scores at each timepoint indicate worse performance (variables that went in the opposite direction were reflected in order to have all variables have the same direction). When examining the change in Composite Drive Score (this outcome variable), a higher score indicates a decline in performance (e.g., Time 2 minus Time 1).
Time frame: Participants are assessed pre-smoking, and then approximately 30m, 1h 30m, 3h 30m and 4h 30m post-smoking
| Arm | Measure | Group | Value (MEAN) | Dispersion |
|---|---|---|---|---|
| Placebo | Change in Composite Drive Score (CDS) From Pre-smoking Simulation | 3h 30min | -.23 z-score | Standard Deviation 0.59 |
| Placebo | Change in Composite Drive Score (CDS) From Pre-smoking Simulation | 1h 30min | -.13 z-score | Standard Deviation 0.61 |
| Placebo | Change in Composite Drive Score (CDS) From Pre-smoking Simulation | Pre-smoke | -.09 z-score | Standard Deviation 0.64 |
| Placebo | Change in Composite Drive Score (CDS) From Pre-smoking Simulation | 30 minutes | -.17 z-score | Standard Deviation 0.61 |
| Placebo | Change in Composite Drive Score (CDS) From Pre-smoking Simulation | 4h 30min | -.07 z-score | Standard Deviation 0.66 |
| 5.9% THC | Change in Composite Drive Score (CDS) From Pre-smoking Simulation | 1h 30min | .40 z-score | Standard Deviation 0.66 |
| 5.9% THC | Change in Composite Drive Score (CDS) From Pre-smoking Simulation | Pre-smoke | .12 z-score | Standard Deviation 0.58 |
| 5.9% THC | Change in Composite Drive Score (CDS) From Pre-smoking Simulation | 30 minutes | .46 z-score | Standard Deviation 0.6 |
| 5.9% THC | Change in Composite Drive Score (CDS) From Pre-smoking Simulation | 3h 30min | .15 z-score | Standard Deviation 0.64 |
| 5.9% THC | Change in Composite Drive Score (CDS) From Pre-smoking Simulation | 4h 30min | .09 z-score | Standard Deviation 0.57 |
| 13.4% THC | Change in Composite Drive Score (CDS) From Pre-smoking Simulation | 4h 30min | .05 z-score | Standard Deviation 0.59 |
| 13.4% THC | Change in Composite Drive Score (CDS) From Pre-smoking Simulation | 3h 30min | .04 z-score | Standard Deviation 0.57 |
| 13.4% THC | Change in Composite Drive Score (CDS) From Pre-smoking Simulation | Pre-smoke | .01 z-score | Standard Deviation 0.52 |
| 13.4% THC | Change in Composite Drive Score (CDS) From Pre-smoking Simulation | 1h 30min | .32 z-score | Standard Deviation 0.59 |
| 13.4% THC | Change in Composite Drive Score (CDS) From Pre-smoking Simulation | 30 minutes | .21 z-score | Standard Deviation 0.6 |
p-value: <0.001Generalized least squares model
Secondary
Simulator: Car Following - Coherence
Coherence is the correlation (0 to 1) between the participant and the lead car (which speeds up and slows down), representing the participant's ability to accurately speed up and slow down similarly to the lead car. Range of scores is from .01 to .97. A higher score is a better score.
Time frame: Participants are assessed pre-smoking, and then approximately 30m, 1h 30m, 3h 30m and 4h 30m post-smoking
| Arm | Measure | Group | Value (MEAN) | Dispersion |
|---|---|---|---|---|
| Placebo | Simulator: Car Following - Coherence | 30 min | .79 Correlation coefficient | Standard Deviation 0.13 |
| Placebo | Simulator: Car Following - Coherence | 3h 30min | .80 Correlation coefficient | Standard Deviation 0.15 |
| Placebo | Simulator: Car Following - Coherence | Pre-smoking | .76 Correlation coefficient | Standard Deviation 0.19 |
| Placebo | Simulator: Car Following - Coherence | 1h 30min | .77 Correlation coefficient | Standard Deviation 0.16 |
| Placebo | Simulator: Car Following - Coherence | 4h 30min | .75 Correlation coefficient | Standard Deviation 0.16 |
| 5.9% THC | Simulator: Car Following - Coherence | 1h 30min | .65 Correlation coefficient | Standard Deviation 0.23 |
| 5.9% THC | Simulator: Car Following - Coherence | 3h 30min | .74 Correlation coefficient | Standard Deviation 0.18 |
| 5.9% THC | Simulator: Car Following - Coherence | 4h 30min | .74 Correlation coefficient | Standard Deviation 0.18 |
| 5.9% THC | Simulator: Car Following - Coherence | 30 min | .66 Correlation coefficient | Standard Deviation 0.2 |
| 5.9% THC | Simulator: Car Following - Coherence | Pre-smoking | .73 Correlation coefficient | Standard Deviation 0.18 |
| 13.4% THC | Simulator: Car Following - Coherence | 4h 30min | .71 Correlation coefficient | Standard Deviation 0.17 |
| 13.4% THC | Simulator: Car Following - Coherence | Pre-smoking | .76 Correlation coefficient | Standard Deviation 0.15 |
| 13.4% THC | Simulator: Car Following - Coherence | 30 min | .71 Correlation coefficient | Standard Deviation 0.17 |
| 13.4% THC | Simulator: Car Following - Coherence | 1h 30min | .68 Correlation coefficient | Standard Deviation 0.19 |
| 13.4% THC | Simulator: Car Following - Coherence | 3h 30min | .74 Correlation coefficient | Standard Deviation 0.17 |
p-value: 0.024Generalized least squares model
Secondary
Simulator: Correct Hits on mSuRT
The number of times the participant touched the correct stimulus (circle) on the iPad, during modified Surrogate Reference Task (mSuRT). Range is from 8 to 32. A higher score is a better score.
Time frame: Participants are assessed pre-smoking, and then approximately 30m, 1h 30m, 3h 30m and 4h 30m post-smoking
| Arm | Measure | Group | Value (MEAN) | Dispersion |
|---|---|---|---|---|
| Placebo | Simulator: Correct Hits on mSuRT | 3h 30min | 30.4 count of correct responses | Standard Deviation 2.73 |
| Placebo | Simulator: Correct Hits on mSuRT | 1h 30min | 30.3 count of correct responses | Standard Deviation 2.16 |
| Placebo | Simulator: Correct Hits on mSuRT | Pre-smoking | 30.7 count of correct responses | Standard Deviation 1.8 |
| Placebo | Simulator: Correct Hits on mSuRT | 30 min | 30.9 count of correct responses | Standard Deviation 1.71 |
| Placebo | Simulator: Correct Hits on mSuRT | 4h 30min | 31.0 count of correct responses | Standard Deviation 1.44 |
| 5.9% THC | Simulator: Correct Hits on mSuRT | 1h 30min | 29.6 count of correct responses | Standard Deviation 2.56 |
| 5.9% THC | Simulator: Correct Hits on mSuRT | Pre-smoking | 29.9 count of correct responses | Standard Deviation 2.76 |
| 5.9% THC | Simulator: Correct Hits on mSuRT | 30 min | 28.7 count of correct responses | Standard Deviation 4.23 |
| 5.9% THC | Simulator: Correct Hits on mSuRT | 3h 30min | 29.7 count of correct responses | Standard Deviation 2.61 |
| 5.9% THC | Simulator: Correct Hits on mSuRT | 4h 30min | 30.3 count of correct responses | Standard Deviation 2.65 |
| 13.4% THC | Simulator: Correct Hits on mSuRT | 4h 30min | 31.1 count of correct responses | Standard Deviation 1.05 |
| 13.4% THC | Simulator: Correct Hits on mSuRT | 3h 30min | 30.7 count of correct responses | Standard Deviation 1.4 |
| 13.4% THC | Simulator: Correct Hits on mSuRT | Pre-smoking | 30.6 count of correct responses | Standard Deviation 1.42 |
| 13.4% THC | Simulator: Correct Hits on mSuRT | 1h 30min | 30.4 count of correct responses | Standard Deviation 1.69 |
| 13.4% THC | Simulator: Correct Hits on mSuRT | 30 min | 30.3 count of correct responses | Standard Deviation 2.54 |
p-value: 0.0503Generalized estimating equations model
Secondary
Simulator: Distance From Lead Car - Car Following
The outcome is distance from the lead car (in virtual feet) during the Car Following Task
Time frame: Participants are assessed pre-smoking, and then approximately 30m, 1h 30m, 3h 30m and 4h 30m post-smoking
| Arm | Measure | Group | Value (MEAN) | Dispersion |
|---|---|---|---|---|
| Placebo | Simulator: Distance From Lead Car - Car Following | 3h 30min | 129 feet | Standard Deviation 33 |
| Placebo | Simulator: Distance From Lead Car - Car Following | 1h 30min | 144 feet | Standard Deviation 34 |
| Placebo | Simulator: Distance From Lead Car - Car Following | Pre-smoking | 153 feet | Standard Deviation 41 |
| Placebo | Simulator: Distance From Lead Car - Car Following | 30 min | 143 feet | Standard Deviation 36 |
| Placebo | Simulator: Distance From Lead Car - Car Following | 4h 30min | 138 feet | Standard Deviation 34 |
| 5.9% THC | Simulator: Distance From Lead Car - Car Following | 1h 30min | 160 feet | Standard Deviation 38 |
| 5.9% THC | Simulator: Distance From Lead Car - Car Following | Pre-smoking | 156 feet | Standard Deviation 41 |
| 5.9% THC | Simulator: Distance From Lead Car - Car Following | 30 min | 165 feet | Standard Deviation 39 |
| 5.9% THC | Simulator: Distance From Lead Car - Car Following | 3h 30min | 137 feet | Standard Deviation 37 |
| 5.9% THC | Simulator: Distance From Lead Car - Car Following | 4h 30min | 136 feet | Standard Deviation 37 |
| 13.4% THC | Simulator: Distance From Lead Car - Car Following | 4h 30min | 151 feet | Standard Deviation 36 |
| 13.4% THC | Simulator: Distance From Lead Car - Car Following | 3h 30min | 150 feet | Standard Deviation 34 |
| 13.4% THC | Simulator: Distance From Lead Car - Car Following | Pre-smoking | 163 feet | Standard Deviation 35 |
| 13.4% THC | Simulator: Distance From Lead Car - Car Following | 1h 30min | 165 feet | Standard Deviation 36 |
| 13.4% THC | Simulator: Distance From Lead Car - Car Following | 30 min | 164 feet | Standard Deviation 39 |
p-value: 0.005Generalized least squares model
Secondary
Simulator: Response Delay - Car Following
Time delay (in seconds) in responding to changes in the lead car's speed. Range is from -5.8 to 6.0. A higher score indicates a worse score.
Time frame: Participants are assessed pre-smoking, and then approximately 30m, 1h 30m, 3h 30m and 4h 30m post-smoking
| Arm | Measure | Group | Value (MEAN) | Dispersion |
|---|---|---|---|---|
| Placebo | Simulator: Response Delay - Car Following | 3h 30min | 2.61 seconds | Standard Deviation 1.04 |
| Placebo | Simulator: Response Delay - Car Following | 1h 30min | 2.80 seconds | Standard Deviation 0.99 |
| Placebo | Simulator: Response Delay - Car Following | Pre-smoking | 2.92 seconds | Standard Deviation 1.15 |
| Placebo | Simulator: Response Delay - Car Following | 30 min | 2.86 seconds | Standard Deviation 1.05 |
| Placebo | Simulator: Response Delay - Car Following | 4h 30min | 2.93 seconds | Standard Deviation 1.05 |
| 5.9% THC | Simulator: Response Delay - Car Following | 1h 30min | 3.25 seconds | Standard Deviation 1.28 |
| 5.9% THC | Simulator: Response Delay - Car Following | Pre-smoking | 3.32 seconds | Standard Deviation 1.23 |
| 5.9% THC | Simulator: Response Delay - Car Following | 30 min | 3.44 seconds | Standard Deviation 1.15 |
| 5.9% THC | Simulator: Response Delay - Car Following | 3h 30min | 2.83 seconds | Standard Deviation 1.05 |
| 5.9% THC | Simulator: Response Delay - Car Following | 4h 30min | 3.00 seconds | Standard Deviation 1.1 |
| 13.4% THC | Simulator: Response Delay - Car Following | 4h 30min | 3.50 seconds | Standard Deviation 1.17 |
| 13.4% THC | Simulator: Response Delay - Car Following | 3h 30min | 3.23 seconds | Standard Deviation 1.18 |
| 13.4% THC | Simulator: Response Delay - Car Following | Pre-smoking | 3.58 seconds | Standard Deviation 1.24 |
| 13.4% THC | Simulator: Response Delay - Car Following | 1h 30min | 3.49 seconds | Standard Deviation 1.04 |
| 13.4% THC | Simulator: Response Delay - Car Following | 30 min | 3.55 seconds | Standard Deviation 1.06 |
p-value: 0.716Generalized least squares model
Secondary
Simulator: Speed Deviation
The variability in speed during the modified Surrogate Reference Test (mSuRT). The speed is in miles per hour. Range is from .17 to 12.85. A higher score indicates worse performance.
Time frame: Participants are assessed pre-smoking, and then approximately 30m, 1h 30m, 3h 30m and 4h 30m post-smoking
| Arm | Measure | Group | Value (MEAN) | Dispersion |
|---|---|---|---|---|
| Placebo | Simulator: Speed Deviation | 3h 30min | 2.15 miles per hour | Standard Deviation 1.89 |
| Placebo | Simulator: Speed Deviation | 1h 30min | 2.49 miles per hour | Standard Deviation 1.7 |
| Placebo | Simulator: Speed Deviation | Pre-smoking | 2.13 miles per hour | Standard Deviation 1.81 |
| Placebo | Simulator: Speed Deviation | 30 min | 2.03 miles per hour | Standard Deviation 1.31 |
| Placebo | Simulator: Speed Deviation | 4h 30min | 2.34 miles per hour | Standard Deviation 1.82 |
| 5.9% THC | Simulator: Speed Deviation | 1h 30min | 2.97 miles per hour | Standard Deviation 1.93 |
| 5.9% THC | Simulator: Speed Deviation | Pre-smoking | 2.61 miles per hour | Standard Deviation 1.97 |
| 5.9% THC | Simulator: Speed Deviation | 30 min | 3.04 miles per hour | Standard Deviation 1.71 |
| 5.9% THC | Simulator: Speed Deviation | 3h 30min | 3.04 miles per hour | Standard Deviation 2.16 |
| 5.9% THC | Simulator: Speed Deviation | 4h 30min | 2.92 miles per hour | Standard Deviation 2.1 |
| 13.4% THC | Simulator: Speed Deviation | 4h 30min | 2.34 miles per hour | Standard Deviation 1.71 |
| 13.4% THC | Simulator: Speed Deviation | 3h 30min | 2.65 miles per hour | Standard Deviation 1.72 |
| 13.4% THC | Simulator: Speed Deviation | Pre-smoking | 2.63 miles per hour | Standard Deviation 1.98 |
| 13.4% THC | Simulator: Speed Deviation | 1h 30min | 3.01 miles per hour | Standard Deviation 2.03 |
| 13.4% THC | Simulator: Speed Deviation | 30 min | 2.99 miles per hour | Standard Deviation 2.05 |
p-value: 0.283Generalized least squares model
Secondary
Simulator: Standard Deviation of Lateral Position (SDLP)
This measures the standard deviation of lateral (lane) position, or the degree to which the participant swerves within the road lane on the driving simulation during the modified Surrogate Reference Task (mSuRT). The range is from .39 to 3.33. A higher score indicates worse performance.
Time frame: Participants are assessed pre-smoking, and then approximately 30m, 1h 30m, 3h 30m and 4h 30m post-smoking
| Arm | Measure | Group | Value (MEAN) | Dispersion |
|---|---|---|---|---|
| Placebo | Simulator: Standard Deviation of Lateral Position (SDLP) | 3h 30min | 1.10 z-score | Standard Deviation 0.31 |
| Placebo | Simulator: Standard Deviation of Lateral Position (SDLP) | 1h 30min | 1.06 z-score | Standard Deviation 0.31 |
| Placebo | Simulator: Standard Deviation of Lateral Position (SDLP) | Pre-smoking | 1.09 z-score | Standard Deviation 0.36 |
| Placebo | Simulator: Standard Deviation of Lateral Position (SDLP) | 30 min | 1.07 z-score | Standard Deviation 0.33 |
| Placebo | Simulator: Standard Deviation of Lateral Position (SDLP) | 4h 30min | 1.10 z-score | Standard Deviation 0.36 |
| 5.9% THC | Simulator: Standard Deviation of Lateral Position (SDLP) | 1h 30min | 1.31 z-score | Standard Deviation 0.39 |
| 5.9% THC | Simulator: Standard Deviation of Lateral Position (SDLP) | Pre-smoking | 1.20 z-score | Standard Deviation 0.36 |
| 5.9% THC | Simulator: Standard Deviation of Lateral Position (SDLP) | 30 min | 1.24 z-score | Standard Deviation 0.36 |
| 5.9% THC | Simulator: Standard Deviation of Lateral Position (SDLP) | 3h 30min | 1.25 z-score | Standard Deviation 0.35 |
| 5.9% THC | Simulator: Standard Deviation of Lateral Position (SDLP) | 4h 30min | 1.25 z-score | Standard Deviation 0.37 |
| 13.4% THC | Simulator: Standard Deviation of Lateral Position (SDLP) | 4h 30min | 1.18 z-score | Standard Deviation 0.42 |
| 13.4% THC | Simulator: Standard Deviation of Lateral Position (SDLP) | 3h 30min | 1.20 z-score | Standard Deviation 0.42 |
| 13.4% THC | Simulator: Standard Deviation of Lateral Position (SDLP) | Pre-smoking | 1.11 z-score | Standard Deviation 0.35 |
| 13.4% THC | Simulator: Standard Deviation of Lateral Position (SDLP) | 1h 30min | 1.23 z-score | Standard Deviation 0.42 |
| 13.4% THC | Simulator: Standard Deviation of Lateral Position (SDLP) | 30 min | 1.19 z-score | Standard Deviation 0.36 |
p-value: 0.022Generalized least squares model
Secondary
Tablet Assessment: Balance
While standing and keeping their feet still, this is a measure of the participant's sway, which is the total distance that the participant's body moved (in meters) from his/her initial vertical position. This was measured using an accelerometer placed on the participant's back. The range of scores is from .222 to 1.661. A higher score indicates worse performance.
Time frame: Participants assessed pre-smoking and 1 hour, 2 hours, 4 hours, and 5 hours after smoking
| Arm | Measure | Group | Value (MEAN) | Dispersion |
|---|---|---|---|---|
| Placebo | Tablet Assessment: Balance | 4 hours | 0.354 meters | Standard Deviation 0.058 |
| Placebo | Tablet Assessment: Balance | 2 hours | 0.351 meters | Standard Deviation 0.053 |
| Placebo | Tablet Assessment: Balance | Pre-smoking | 0.358 meters | Standard Deviation 0.058 |
| Placebo | Tablet Assessment: Balance | 1 hour | 0.342 meters | Standard Deviation 0.054 |
| Placebo | Tablet Assessment: Balance | 5 hours | 0.368 meters | Standard Deviation 0.059 |
| 5.9% THC | Tablet Assessment: Balance | 2 hours | 0.394 meters | Standard Deviation 0.161 |
| 5.9% THC | Tablet Assessment: Balance | Pre-smoking | 0.360 meters | Standard Deviation 0.067 |
| 5.9% THC | Tablet Assessment: Balance | 1 hour | 0.376 meters | Standard Deviation 0.09 |
| 5.9% THC | Tablet Assessment: Balance | 4 hours | 0.386 meters | Standard Deviation 0.131 |
| 5.9% THC | Tablet Assessment: Balance | 5 hours | 0.371 meters | Standard Deviation 0.054 |
| 13.4% THC | Tablet Assessment: Balance | 5 hours | 0.365 meters | Standard Deviation 0.072 |
| 13.4% THC | Tablet Assessment: Balance | 4 hours | 0.377 meters | Standard Deviation 0.133 |
| 13.4% THC | Tablet Assessment: Balance | Pre-smoking | 0.356 meters | Standard Deviation 0.058 |
| 13.4% THC | Tablet Assessment: Balance | 2 hours | 0.414 meters | Standard Deviation 0.254 |
| 13.4% THC | Tablet Assessment: Balance | 1 hour | 0.363 meters | Standard Deviation 0.129 |
p-value: 0.144Generalized least squares model
Secondary
Tablet Assessment: Dual Attention Missed Switches
The participant follows a moving target (square) with her/his finger, and switches to following a new stimulus when it appears in the corner of the screen. Each participant was classified as to whether he/she missed any of these switches during the trial. The outcome is the proportion of participants within each group who missed at least one switch. The range is from 0 to 1. Higher indicates a worse score.
Time frame: Participants assessed pre-smoking and 1 hour, 2 hours, 4 hours, and 5 hours after smoking
| Arm | Measure | Group | Value (MEAN) |
|---|---|---|---|
| Placebo | Tablet Assessment: Dual Attention Missed Switches | 4 hours | 0.191 Proportion of participants |
| Placebo | Tablet Assessment: Dual Attention Missed Switches | 2 hours | 0.175 Proportion of participants |
| Placebo | Tablet Assessment: Dual Attention Missed Switches | Pre-smoking | 0.095 Proportion of participants |
| Placebo | Tablet Assessment: Dual Attention Missed Switches | 1 hour | 0.095 Proportion of participants |
| Placebo | Tablet Assessment: Dual Attention Missed Switches | 5 hours | 0.095 Proportion of participants |
| 5.9% THC | Tablet Assessment: Dual Attention Missed Switches | 2 hours | 0.161 Proportion of participants |
| 5.9% THC | Tablet Assessment: Dual Attention Missed Switches | Pre-smoking | 0.145 Proportion of participants |
| 5.9% THC | Tablet Assessment: Dual Attention Missed Switches | 1 hour | 0.194 Proportion of participants |
| 5.9% THC | Tablet Assessment: Dual Attention Missed Switches | 4 hours | 0.177 Proportion of participants |
| 5.9% THC | Tablet Assessment: Dual Attention Missed Switches | 5 hours | 0.129 Proportion of participants |
| 13.4% THC | Tablet Assessment: Dual Attention Missed Switches | 5 hours | 0.183 Proportion of participants |
| 13.4% THC | Tablet Assessment: Dual Attention Missed Switches | 4 hours | 0.167 Proportion of participants |
| 13.4% THC | Tablet Assessment: Dual Attention Missed Switches | Pre-smoking | 0.167 Proportion of participants |
| 13.4% THC | Tablet Assessment: Dual Attention Missed Switches | 2 hours | 0.233 Proportion of participants |
| 13.4% THC | Tablet Assessment: Dual Attention Missed Switches | 1 hour | 0.183 Proportion of participants |
p-value: 0.366Generalized Estimating Equations model
Secondary
Tablet Assessment: Lane Tracking Standard Deviation
The participant is to rotate the iPad in order to keep a round object in the center, between two lines (lanes). This measure is the standard deviation of the position of the round object during the task (in essence, how much swerving there is within the lane). The range is from 8.2 to 189.4. A higher score indicates worse performance.
Time frame: Participants assessed pre-smoking and 1 hour, 2 hours, 4 hours, and 5 hours after smoking
| Arm | Measure | Group | Value (MEAN) | Dispersion |
|---|---|---|---|---|
| Placebo | Tablet Assessment: Lane Tracking Standard Deviation | 4 hours | 28.1 standard deviation of position | Standard Deviation 13.3 |
| Placebo | Tablet Assessment: Lane Tracking Standard Deviation | 2 hours | 28.4 standard deviation of position | Standard Deviation 10.3 |
| Placebo | Tablet Assessment: Lane Tracking Standard Deviation | Pre-smoking | 26.9 standard deviation of position | Standard Deviation 9.53 |
| Placebo | Tablet Assessment: Lane Tracking Standard Deviation | 1 hour | 28.7 standard deviation of position | Standard Deviation 13.4 |
| Placebo | Tablet Assessment: Lane Tracking Standard Deviation | 5 hours | 26.4 standard deviation of position | Standard Deviation 10.8 |
| 5.9% THC | Tablet Assessment: Lane Tracking Standard Deviation | 2 hours | 27.6 standard deviation of position | Standard Deviation 10.2 |
| 5.9% THC | Tablet Assessment: Lane Tracking Standard Deviation | Pre-smoking | 30.9 standard deviation of position | Standard Deviation 23.7 |
| 5.9% THC | Tablet Assessment: Lane Tracking Standard Deviation | 1 hour | 30.9 standard deviation of position | Standard Deviation 15.7 |
| 5.9% THC | Tablet Assessment: Lane Tracking Standard Deviation | 4 hours | 29.9 standard deviation of position | Standard Deviation 15.5 |
| 5.9% THC | Tablet Assessment: Lane Tracking Standard Deviation | 5 hours | 25.4 standard deviation of position | Standard Deviation 8.39 |
| 13.4% THC | Tablet Assessment: Lane Tracking Standard Deviation | 5 hours | 25.3 standard deviation of position | Standard Deviation 13.8 |
| 13.4% THC | Tablet Assessment: Lane Tracking Standard Deviation | 4 hours | 28.6 standard deviation of position | Standard Deviation 14.8 |
| 13.4% THC | Tablet Assessment: Lane Tracking Standard Deviation | Pre-smoking | 27.2 standard deviation of position | Standard Deviation 9.67 |
| 13.4% THC | Tablet Assessment: Lane Tracking Standard Deviation | 2 hours | 27.4 standard deviation of position | Standard Deviation 10.4 |
| 13.4% THC | Tablet Assessment: Lane Tracking Standard Deviation | 1 hour | 32.1 standard deviation of position | Standard Deviation 21.7 |
p-value: 0.225Generalized least squares model
Secondary
Tablet Assessment: Time Estimation
The participant is to estimate the amount of time that has passed while performing a secondary task. This outcome is the ratio of 1) the estimated time that has passed (seconds), divided by 2) the actual amount of time that has passed. The range is from 0.204 to 1.89. A higher score indicates a better performance.
Time frame: Participants assessed pre-smoking and 1 hour, 2 hours, 4 hours, and 5 hours after smoking
| Arm | Measure | Group | Value (MEAN) | Dispersion |
|---|---|---|---|---|
| Placebo | Tablet Assessment: Time Estimation | 4 hours | 0.85 Ratio of estimated/actual time | Standard Deviation 0.23 |
| Placebo | Tablet Assessment: Time Estimation | 2 hours | 0.83 Ratio of estimated/actual time | Standard Deviation 0.2 |
| Placebo | Tablet Assessment: Time Estimation | Pre-smoking | 0.75 Ratio of estimated/actual time | Standard Deviation 0.19 |
| Placebo | Tablet Assessment: Time Estimation | 1 hour | 0.79 Ratio of estimated/actual time | Standard Deviation 0.21 |
| Placebo | Tablet Assessment: Time Estimation | 5 hours | 0.83 Ratio of estimated/actual time | Standard Deviation 0.2 |
| 5.9% THC | Tablet Assessment: Time Estimation | 2 hours | 0.96 Ratio of estimated/actual time | Standard Deviation 0.3 |
| 5.9% THC | Tablet Assessment: Time Estimation | Pre-smoking | 0.83 Ratio of estimated/actual time | Standard Deviation 0.3 |
| 5.9% THC | Tablet Assessment: Time Estimation | 1 hour | 0.89 Ratio of estimated/actual time | Standard Deviation 0.3 |
| 5.9% THC | Tablet Assessment: Time Estimation | 4 hours | 0.93 Ratio of estimated/actual time | Standard Deviation 0.23 |
| 5.9% THC | Tablet Assessment: Time Estimation | 5 hours | 0.89 Ratio of estimated/actual time | Standard Deviation 0.28 |
| 13.4% THC | Tablet Assessment: Time Estimation | 5 hours | 0.85 Ratio of estimated/actual time | Standard Deviation 0.21 |
| 13.4% THC | Tablet Assessment: Time Estimation | 4 hours | 0.86 Ratio of estimated/actual time | Standard Deviation 0.21 |
| 13.4% THC | Tablet Assessment: Time Estimation | Pre-smoking | 0.77 Ratio of estimated/actual time | Standard Deviation 0.22 |
| 13.4% THC | Tablet Assessment: Time Estimation | 2 hours | 0.87 Ratio of estimated/actual time | Standard Deviation 0.27 |
| 13.4% THC | Tablet Assessment: Time Estimation | 1 hour | 0.85 Ratio of estimated/actual time | Standard Deviation 0.24 |
p-value: 0.294Generalized least squares model
Secondary
Tablet Assessment: Visual Spatial Learning Test Number Correct
Assessment of short-term memory for abstract figures. The participant is to memorize abstract figures and their locations on a 3 x 3 grid. After initial viewing (10 seconds), the figures go away for either 4, 12, or 24 seconds. The participant is then to identify which figures were in the initial viewing (from a list at the bottom of the screen), and place them at the correct location. This is the number of correctly identified figures. The range is from 0 to 12. A higher score indicates better performance.
Time frame: Participants assessed pre-smoking and 1 hour, 2 hours, 4 hours, and 5 hours after smoking
| Arm | Measure | Group | Value (MEAN) | Dispersion |
|---|---|---|---|---|
| Placebo | Tablet Assessment: Visual Spatial Learning Test Number Correct | 4 hours | 8.5 number of correct responses | Standard Deviation 3 |
| Placebo | Tablet Assessment: Visual Spatial Learning Test Number Correct | 2 hours | 8.9 number of correct responses | Standard Deviation 3.1 |
| Placebo | Tablet Assessment: Visual Spatial Learning Test Number Correct | Pre-smoking | 9.9 number of correct responses | Standard Deviation 2.3 |
| Placebo | Tablet Assessment: Visual Spatial Learning Test Number Correct | 1 hour | 9.1 number of correct responses | Standard Deviation 2.8 |
| Placebo | Tablet Assessment: Visual Spatial Learning Test Number Correct | 5 hours | 9.3 number of correct responses | Standard Deviation 2.9 |
| 5.9% THC | Tablet Assessment: Visual Spatial Learning Test Number Correct | 2 hours | 8.7 number of correct responses | Standard Deviation 2.6 |
| 5.9% THC | Tablet Assessment: Visual Spatial Learning Test Number Correct | Pre-smoking | 9.7 number of correct responses | Standard Deviation 2.7 |
| 5.9% THC | Tablet Assessment: Visual Spatial Learning Test Number Correct | 1 hour | 8.4 number of correct responses | Standard Deviation 2.6 |
| 5.9% THC | Tablet Assessment: Visual Spatial Learning Test Number Correct | 4 hours | 8.3 number of correct responses | Standard Deviation 2.9 |
| 5.9% THC | Tablet Assessment: Visual Spatial Learning Test Number Correct | 5 hours | 8.5 number of correct responses | Standard Deviation 3 |
| 13.4% THC | Tablet Assessment: Visual Spatial Learning Test Number Correct | 5 hours | 9.5 number of correct responses | Standard Deviation 3 |
| 13.4% THC | Tablet Assessment: Visual Spatial Learning Test Number Correct | 4 hours | 8.8 number of correct responses | Standard Deviation 2.5 |
| 13.4% THC | Tablet Assessment: Visual Spatial Learning Test Number Correct | Pre-smoking | 10.1 number of correct responses | Standard Deviation 2.2 |
| 13.4% THC | Tablet Assessment: Visual Spatial Learning Test Number Correct | 2 hours | 8.9 number of correct responses | Standard Deviation 2.7 |
| 13.4% THC | Tablet Assessment: Visual Spatial Learning Test Number Correct | 1 hour | 9.3 number of correct responses | Standard Deviation 2.7 |
p-value: 0.592Generalized least squares model
Secondary
THC Concentrations: Correlation Between Blood and Oral Fluid
Spearman's correlation between THC concentrations in whole blood and oral fluid. Higher scores are better.
Time frame: Approximately 15 minutes post-smoking
| Arm | Measure | Value (NUMBER) |
|---|---|---|
| Placebo | THC Concentrations: Correlation Between Blood and Oral Fluid | 0.217 Spearman's rho |
| 5.9% THC | THC Concentrations: Correlation Between Blood and Oral Fluid | 0.414 Spearman's rho |
| 13.4% THC | THC Concentrations: Correlation Between Blood and Oral Fluid | 0.249 Spearman's rho |
p-value: 0.09Spearman's correlation
p-value: 0.0006Spearman's correlation
p-value: 0.053Spearman's correlation
Secondary
THC Concentrations: Correlation Between Whole Blood and Breath
Spearman's correlation between THC concentrations in whole blood and breath
Time frame: Approximately 15 minutes post-smoking
| Arm | Measure | Value (NUMBER) |
|---|---|---|
| Placebo | THC Concentrations: Correlation Between Whole Blood and Breath | 0.134 Spearman's rho |
| 5.9% THC | THC Concentrations: Correlation Between Whole Blood and Breath | -0.258 Spearman's rho |
| 13.4% THC | THC Concentrations: Correlation Between Whole Blood and Breath | -0.176 Spearman's rho |
p-value: 0.3Spearman's correlation
p-value: 0.038Spearman's correlation
p-value: 0.175Spearman's correlation