Can alcohol and cannabis together worsen driving skills more than either alone?
NCT ID NCT03106363
First seen Jul 24, 2026 · Last updated Jul 24, 2026
Summary
This trial investigates how combining alcohol and cannabis affects driving performance in young adults aged 19 to 29. Participants drink alcohol or a placebo and smoke a cannabis or placebo cigarette, then complete driving scenarios on a high-fidelity simulator. The study measures lane control, speed, and other driving-related skills to understand the combined risks of these substances.
What this could mean
Our plain-language read of the trial. This is informational only, not medical advice or a prediction.
- Active substance
- alcohol and cannabis (delta-9-tetrahydrocannabinol) given separately and together
- What this could lead to
- If this trial clarifies how alcohol and cannabis together impair driving, it could inform public safety messages and policies to reduce crash risk in young drivers.
- What could go wrong
- This is a small, early-stage lab study using a driving simulator, not real roads. Results may not fully reflect real-world driving or apply to all age groups.
This is an AI summary of the original study and may miss details. Read our disclaimer.
Study facts
What this study's own registry entry says, in plain language.
- Phase
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Not a phased trial
Phase numbers describe drug development. The registry uses this when they do not apply, as it does for trials of devices, procedures or behaviour changes, and for observational studies.
- Participants
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49 people
The number who actually took part.
- Started
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Jul 2017
- Finished
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Jan 2020
- Lead sponsor
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Other sponsor
The registry's catch-all category, for sponsors it does not file as a company, a government agency, or a research network.
Who can take part
This study's own entry requirements. Only the study team can say for certain whether you qualify.
- Ages
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19 to 29 years
- Sex
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Anyone
- Healthy volunteers
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Accepted
You do not need to have the condition being studied to take part.
Show the full entry requirements Hide the full entry requirements
Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.
Inclusion Criteria: * Use of cannabis at least once a week confirmed by urine point-of-care testing; * Males who report consuming at least 5 drinks and females who report consuming at least 4 drinks in about 2 hours in the past 6 months and at least one episode of rapid alcohol consumption in the past 6 months (3 or more drinks over a span of one hour) * 19-29 years of age; * 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 48 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 the duration of the study; * Provides written and informed consent. Exclusion Criteria: * Urine toxicology screens negative for cannabis upon eligibility assessment; * Diagnosis of severe medical or psychiatric conditions; * Females: Pregnancy or breastfeeding; * Meets criteria for Alcohol or Substance Dependence (current or lifetime) (DSM-IV); * Is a regular user of medications that affect brain function (i.e., antidepressants, benzodiazepines, stimulants); * Taking medications or have any medical condition for which alcohol is contraindicated; * First-degree relative diagnosed with schizophrenia; * Severe allergy to citrus (lemon-lime).
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Conditions
The condition(s) this trial relates to.
As listed by the trial registrant
The condition terms exactly as the trial's registrant entered them.
Contacts and locations
Locations
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Centre for Addiction and Mental Health
Toronto, Ontario, M5S 2S1, Canada