Cannabis Effects on Driving-related Skills of Young Drivers

• 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.

• Area under the blood concentration versus time curves for delta-9-tetrahydrocannabinol, carboxy-tetrahydrocannabinol, and 11-hydroxy-tetrahydrocannabinol [ 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 ]
• 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 ration [ 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.

Motor vehicle collisions are the leading cause of death for young people. The investigators have recently found that driving after using cannabis is more common among young Canadian drivers than driving after drinking. While this observation raises concerns, the effects of cannabis on driving-related skills in this age group are not well understood. As well, evidence suggests that residual effects of cannabis on driving-related skills may be observed up to 24 hours later. These residual effects may have important implications for the effects of cannabis use on collision risk, but little evidence on them in available. This study will examine the effects of a single dose of cannabis (marijuana) on driving-related skills immediately following consumption, 24 hours later, and 48 hours later. To date, the residual effect at 48 hours has not been examined. A total of 149 subjects aged 19 to 25 years old will be randomly assigned to smoke either a placebo or active cannabis cigarette (12.5% THC potency). Following an eligibility screening and practice session, participants will attend 3 testing days; drug-administration, 24-hour follow-up and 48-hour follow-up. The effects of cannabis/placebo on performance of driving-related skills using a high-fidelity driving simulator will be assessed on each testing day. The effects of cannabis on mood, cognition, memory and complex reaction time will also be assessed. Identifying factors that affect the collision risks experienced by young drivers is a public health priority. While many young people believe that cannabis does not impair driving, some recent studies suggest that these may be very dangerous beliefs. This study will provide important information on how cannabis may affect the driving skills of young drivers, to inform efforts to understand and address cannabis-related collision in this age group.

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.

• Drug: delta-9-tetrahydrocannabinol
  A single cannabis cigarette (potency 12.5% THC) will be given to participants to smoke over a 10 minute period, ad lib. If the cigarette is not smoked in its entirety, the remainder will be weighed to estimate dose.
  Other Names:

  • cannabis sativa
  • marijuana
• Drug: Placebo
  A single placebo cannabis cigarette (0% THC) will be given to participants to smoke over a 10 minute period, ad lib. If the cigarette is not smoked in its entirety, the remainder will be weighed to estimate dose (as this is a double-blind study).
  Other Names:

  • cannabis sativa
  • marijuana

• Active Comparator: Active cannabis
  In this condition, participants will receive a cigarette containing 12.5% active THC.
  Intervention: Drug: delta-9-tetrahydrocannabinol
• Placebo Comparator: Placebo
  In this condition, participants will receive a cannabis cigarette where the active THC has been removed (contains 0% THC).
  Intervention: Drug: Placebo

• Chipman ML, Macdonald S, Mann RE. Being "at fault" in traffic crashes: does alcohol, cannabis, cocaine, or polydrug abuse make a difference? Inj Prev. 2003 Dec;9(4):343-8.
• Laumon B, Gadegbeku B, Martin JL, Biecheler MB; SAM Group. Cannabis intoxication and fatal road crashes in France: population based case-control study. BMJ. 2005 Dec 10;331(7529):1371. Epub 2005 Dec 1. Erratum in: BMJ. 2006 Jun 3;332(7553):1298.
• Siliquini R, Chiadò Piat S, Gianino MM, Renga G. Drivers involved in road traffic accidents in Piedmont Region: psychoactive substances consumption. J Prev Med Hyg. 2007 Dec;48(4):123-8.
• Stoduto G, Vingilis E, Kapur BM, Sheu WJ, McLellan BA, Liban CB. Alcohol and drug use among motor vehicle collision victims admitted to a regional trauma unit: demographic, injury, and crash characteristics. Accid Anal Prev. 1993 Aug;25(4):411-20.
• Drummer OH, Gerostamoulos J, Batziris H, Chu M, Caplehorn J, Robertson MD, Swann P. The involvement of drugs in drivers of motor vehicles killed in Australian road traffic crashes. Accid Anal Prev. 2004 Mar;36(2):239-48.
• Blows S, Ivers RQ, Connor J, Ameratunga S, Woodward M, Norton R. Marijuana use and car crash injury. Addiction. 2005 May;100(5):605-11.
• Asbridge M, Poulin C, Donato A. Motor vehicle collision risk and driving under the influence of cannabis: evidence from adolescents in Atlantic Canada. Accid Anal Prev. 2005 Nov;37(6):1025-34. Epub 2005 Jun 29.
• Adlaf EM, Mann RE, Paglia A. Drinking, cannabis use and driving among Ontario students. CMAJ. 2003 Mar 4;168(5):565-6.
• O'Malley PM, Johnston LD. Drugs and driving by American high school seniors, 2001-2006. J Stud Alcohol Drugs. 2007 Nov;68(6):834-42.
• Pope HG Jr, Gruber AJ, Yurgelun-Todd D. The residual neuropsychological effects of cannabis: the current status of research. Drug Alcohol Depend. 1995 Apr;38(1):25-34. Review.
• Heishman SJ, Huestis MA, Henningfield JE, Cone EJ. Acute and residual effects of marijuana: profiles of plasma THC levels, physiological, subjective, and performance measures. Pharmacol Biochem Behav. 1990 Nov;37(3):561-5.
• Crancer A Jr, Dille JM, Delay JC, Wallace JE, Haykin MD. Comparison of the effects of marihuana and alcohol on simulated driving performance. Science. 1969 May 16;164(3881):851-4.
• Cone EJ, Huestis MA. Relating blood concentrations of tetrahydrocannabinol and metabolites to pharmacologic effects and time of marijuana usage. Ther Drug Monit. 1993 Dec;15(6):527-32. Review.
• Harder S, Rietbrock S. Concentration-effect relationship of delta-9-tetrahydrocannabiol and prediction of psychotropic effects after smoking marijuana. Int J Clin Pharmacol Ther. 1997 Apr;35(4):155-9.
• McLaren J, Swift W, Dillon P, Allsop S. Cannabis potency and contamination: a review of the literature. Addiction. 2008 Jul;103(7):1100-9. Epub 2008 May 20. Review.

Inclusion Criteria:

• Males and females aged 19 to 25
• Regular cannabis users (between one and four times per week)
• Held a valid class G or G2 Ontario driver's license (or equivalent from another jurisdiction) for at least 12 months.
• Willing to abstain from cannabis use for the duration of the study.
• Provides written and informed consent

Exclusion Criteria:

• Positive breathalyzer results for alcohol on any given study day.
• Eligibility screening (session 1) cannot confirm recent cannabis use
• A toxicology screen any time after session 1 indicates that additional cannabis (other than that provided during the study) or any other psychoactive substance has been used.
• Is a regular user of medications that affect brain function (i.e., antidepressant, benzodiazepines, stimulants).
• Diagnosis of severe medical or psychiatric conditions.
• A first degree relative diagnosis of schizophrenia.
• Meets criteria for current or lifetime Substance Use Disorders (DSM-IV) with the exception of nicotine.
• Meets criteria for Cannabis Dependence (DSM-IV).
• Pregnant, are trying to become pregnant, or are currently breastfeeding.

• Canadian Institutes of Health Research (CIHR)
• Health Canada