Age Differences in the Effects of Cannabis on Simulated Driving

Epidemiological studies have established that the use of cannabis can increase the risk of a motor vehicle collision. A number of variables can influence the effects of cannabis on driving. For example, frequent users of cannabis have been shown to have different cognitive and physiological responses to cannabis as compared to occasional users. In addition, we know that younger drivers are more likely to be involved in motor vehicle collisions after alcohol use as compared to older users. The contribution of age and experience with cannabis on cannabis-mediated effects on driving have yet to be delineated in laboratory studies. The purpose of the present investigation will be to determine whether cannabis has different effects on driving in young, as compared to middle aged, drivers. Half of each age group will be occasional users of cannabis and the other half will be frequent users.

Eligible participants will attend the laboratory for two test sessions; in one session they will smoke a cannabis cigarette and in the other they smoke a placebo cigarette. Participants will drive a driving simulator before and after smoking the cigarette. Blood for measurement of THC and metabolites will also be collected before smoking the cigarette and at a number of times after smoking. Subjective and cognitive tasks will be completed before and after smoking.

It is hoped that the findings of this study will help to inform public perception and policy into the potential effects of cannabis on driving.

Inclusion criteria

• 19-25 or 35-45 years of age;
• Use of smoked cannabis at least once in the past 6 months.
• Use of smoked or vaped cannabis primarily for recreational purposes on up to 1 day per week or on at least 6 days per week in the past 3 months;
• Holds a class G or G2 Ontario driver's licence (or equivalent from another jurisdiction) for at least 12 months;
• Willing to abstain from using alcohol for 24 hours and cannabis for 72 hours prior to Practice and Test Sessions;
• Willing to abstain from all other drugs not prescribed for medical purposes for 48 hours prior to Practice and Test Sessions;
• Resides within Toronto (study site) or can reside with friends/family in Toronto after a Test Session; this area may be extended to the Greater Toronto area if recruitment challenges arise;
• Participant willing to use appropriate contraception until their participation in the study is completed;
• Provides written and informed consent.

Exclusion criteria

• Use of cannabis primarily for therapeutic purposes, or equally for therapeutic and recreational purposes;
• Diagnosis of medical condition that contraindicates use of cannabis determined by self-report as judged by the Principal Investigator and a study physician; this includes a history of hypersensitivity to cannabinoids smoke, respiratory disease and/or severe cardiovascular, cerebrovascular, renal or liver disease, and bleeding disorders. Smoking cannabis is not recommended for individuals with respiratory diseases, and they will be excluded;
• Diagnosis of psychiatric condition that contraindicates use of cannabis determined by self-report or SCID-5;
• Participants of childbearing potential: Pregnancy (point-of-care test) or breastfeeding;
• Meets criteria for current or lifetime alcohol or other substance use disorder (DSM-5), except tobacco use disorder and caffeine use disorder;
• Is a regular user of medications that affect brain function (based on self-report); this includes concomitant therapy with sedative-hypnotics or other psychoactive drugs
• Use of anti-hypertensives;
• First-degree relative diagnosed with schizophrenia or another psychotic disorder.
• Participation in a past driving study at CAMH (to limit practice effects).
• Participation in a clinical study concurrent with their participation in this study.