Cannabis Effects on Driving-related Skills of Young Drivers

• Psychomotor impairment (driving) [ Time Frame: at baseline (24 hours and 30 minutes before smoking), 30 minutes, 24 hours and 48 hours after smoking, ] [ Designated as safety issue: No ]
  The driving simulator will objectively measure driving behaviour during a number of pre-programmed driving scenarios designed to test simple and complex reaction time, risk taking, speed, lane deviation, etc.
  
  

• Area under the blood concentration versus time curves for delta-9-tetrahydrocannabinol, carboxy-tetrahydrocannabinol, and 11-hydroxy-tetrahydrocannabinol [ Time Frame: 30 minutes pre-dose. 5, 10, 15, 30 minutes and 1, 2, 3, 4, 5, 6, 24 and 48 hours post-dose ] [ Designated as safety issue: No ]
  
• Vital signs [ Time Frame: 24 hours and 30 minutes pre-dose. 5, 10, 15, 30, minutes and 1, 2, 3, 4, 5, 6, 24, and 48 hours post-dose ] [ Designated as safety issue: No ]
  Blood pressure, pulse, temperature, and respiration rate will be assessed.
  
  
• Subjective drug effects [ Time Frame: 24 hours and 30 minutes pre-dose. 5, 10, 15, 30 minutes and 1, 2, 3, 4, 5, 6, 24 and 48 hours post-dose ] [ Designated as safety issue: Yes ]
  Visual analogue scales will be used to measure subjective pharmacodynamic responses. How participants feel before and after drug administration will be assessed.
  
  
• Cognitive testing [ Time Frame: 24 hours and 30 minutes pre-dose, and 1, 24, and 48 hours post-dose ] [ Designated as safety issue: No ]
  Measures of cognitive ability will be assessed using the Digit Symbol Substitution Test, Hopkins Verbal Learning Test - 2, Continuous Performance Test, and Grooved Pegboard test.
  
  
• Urine carboxy-tetrahydrocannabinol to creatinine ratio [ Time Frame: 30 minutes pre-dose, 6, 24, and 48 hours post dose. ] [ Designated as safety issue: No ]
  Determination of the ratio of excreted THC metabolite carboxy-THC to creatinine (a normal breakdown product of muscle) will determine whether participants have used cannabis between testing days, and hence will be excluded from further participation.
  
  

This study will test the prediction that residual effects of an acute dose of cannabis on driving-related skills will be observed in a group of young drivers 48 hours following a single dose of smoked cannabis, and will also examine the effects of an acute dose of cannabis on those skills using driving simulator technology.

Study Objectives

1. Examine the residual effects of a moderate dose of cannabis (12.5% THC) on driving simulator performance of young drivers. We will test the hypothesis that performance on a high-fidelity driving simulator task will be significantly impaired 24 hours following a dose of cannabis in comparison to a placebo condition.
2. Examine the acute effects of a moderate dose of cannabis (12.5% THC) on driving simulator performance of young drivers. We will also examine the relationship of cannabinoid levels to performance measures in this time frame.
3. Explore the effects of driving history, driving attitudes, and individual difference measures (e.g., demographics, drug and alcohol use, etc.) on the acute and residual effects of cannabis on driving simulator performance of young drivers.

Study Design and Duration

The study is a double-blind, placebo-controlled mixed-design study, including a randomized between-subjects comparison of the effects of smoked cannabis and both between- and within-subjects examination of its residual effects at 24 and 48 hours following one-time drug administration. Although a placebo condition is part of the study, this is not a treatment study.

The study will consist of 5 sessions for each subject (an eligibility screening day, a practice session, and 3 subsequent test days). Breath, blood, and urine samples will be taken to confirm ongoing eligibility. Participants will be asked to smoke a single cannabis cigarette (12.5% THC or placebo). Driving simulator trials (2 x 10 minutes) will be performed before smoking and 30 minutes later. Sequential blood samples will be drawn to permit characterization of cannabinoid levels for time-effect estimation over a 6 hour period. Mood and cognitive functioning questionnaires will be completed before and after smoking, 24, and 48 hours later.

The driving simulations will be programmed to include various driving scenes, potentially frustrating events (e.g., slow vehicles), and will provide the opportunity to speed and race. Trials used for each testing session will be fully counterbalanced over the four testing sessions.