New study aims to create a roadside marijuana impairment test
NCT ID NCT05115513
First seen Jun 27, 2026 · Last updated Jun 27, 2026
Summary
This study, completed by Yale University, tested whether a standardized field test can measure marijuana impairment in drivers. 41 participants who use marijuana regularly completed cognitive tasks and simulated driving after smoking either medium-THC or placebo marijuana. The goal is to develop a reliable test for police to use on the road.
What this could mean
Our plain-language read of the trial. This is informational only, not medical advice or a prediction.
- Active substance
- Marijuana flower with medium THC
- What this could lead to
- If successful, this could lead to a reliable roadside test for marijuana impairment, helping improve road safety.
- What could go wrong
- This is a small, early-phase study (41 participants) that only looks at lab-based tasks, not real driving. Results may not translate to real-world conditions or different populations.
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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Phase 1
The first testing in people. Mainly checks safety and dose, usually in a small group.
- Participants
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41 people
The number who actually took part.
- Started
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Aug 2022
- Finished
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Aug 2023
- 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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18 to 55 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: * 18-55 yrs/ old * Current driver's license and history of repeated highway vehicle driving experience (at least 2 years) * Recent, recurrent CNB use and felt high when used * Able to read, speak, and understand English * Able and willing to provide written informed consent, and willing to commit to the study protocol Exclusion Criteria: * Current marijuana tolerance, desire to cut down, or cravings to use during periods of abstinence * New CNB users who have not used at least once during their lifetime. * Positive screen for drug and alcohol (except THC) on test day will result in rescheduling the appointment * Former CNB users who are abstaining * Pregnancy, breastfeeding, and ineffective birth control methods. * History of adverse psychological or medical effects following cannabis use * serious medical, neuro-ophthalmological, or neurological illness (i.e. cancer, seizure disorders, encephalopathy) * History of head trauma with loss of consciousness \> 30 minutes or concussion lasting 30 days. * IQ \<80 on the Wechsler Abbreviated Scale of Intelligence * Inability to comprehend written instructions using the WRAT 4 reading achievement test * Any medical/neurological condition that could compromise neurocognitive performance (i.e. epilepsy, multiple sclerosis, fetal alcohol syndrome) * Uncontrolled, persistent high blood pressure * Anyone deemed unsafe to study personnel for any reason
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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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Olin Neuropsychiatry Research Center
Hartford, Connecticut, 06106, United States