An interventional study of alcohol and placebo alcohol in Psychomotor Impairment, sponsored by Centre for Addiction and Mental Health. Completed at 1 site in Canada. Open to participants aged 19 Years to 29 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-07-24.
Sponsored by Centre for Addiction and Mental Health · Not applicable, Interventional, and Other
Alcohol and cannabis are the two most widely used substances of abuse in the world and are the psychoactive substances most often found in seriously and fatally injured drivers. In a recent study, it was observed that individuals who reported both driving under the influence of alcohol (DUIA) and the influence of cannabis (DUIC) experienced collision risk that was nearly 4 times that of individuals who reported driving after using only one of these drugs. Recent research in the United States and Canada indicates that the prevalence of DUIC among young drivers of high school and university age, and young adults is similar to, or higher than, the prevalence of DUIA. This is a serious public health issue, since motor vehicle collisions are the leading cause of death in this age group. Given the frequency with which alcohol and cannabis are consumed together, it is important to understand their combined effects on driver behaviour. The current study will examine the acute effects of a moderate dose of cannabis (12.5% THC) combined with an intoxicating amount of alcohol (BAC=0.08) on driving simulator performance of young drivers. Following an eligibility screening and practice session, a total of 70 participants aged 19 to 29 years will each complete 4 experimental sessions. During each session, participants will drink alcohol or placebo alcohol and smoke an active or placebo cannabis cigarette. The effects of alcohol and cannabis on the performance of driving-related skills will be assessed using a high-fidelity driving simulator. Cognitive, psychomotor, and mood effects will also be assessed.
The proposed study will pursue the following primary aims:
Aim 1: Examine the acute effects of a moderate dose of cannabis (12.5% THC) combined with an intoxicating amount of alcohol (BAC=0.08) on driving simulator performance of young drivers. Simulated driving performance, tests of cognition, verbal memory, and mood will be measured concurrently with BAC and levels of cannabinoids in biological fluids before and after acute drug exposure in male and female drivers aged 19 to 29. BAC and biological fluids will be measured up to 5 hours following drug exposure.
Aim 2: Explore the effects of driving history, driving attitudes, and individual difference measures (e.g., demographics, drug and alcohol use, etc.) on the acute effects of alcohol and cannabis on driving simulator performance of young drivers. Exploratory analyses will be undertaken to determine if the acute effects of cannabis plus alcohol on the driving simulator task are influenced by these measures.
Study Design and Duration
This study will be a within-subjects, double-blind, double-dummy, placebo-controlled, counterbalanced, randomized clinical trial assessing the impact of alcohol and cannabis combined on driver behaviour. Although a placebo condition is part of the study, this is not a treatment study.
Initial contact with potential participants will be made via telephone, and study personnel will conduct a telephone screen for eligibility. Upon eligibility confirmation by telephone, participants will be asked to attend CAMH for an eligibility assessment. Participants will attend CAMH for a total of 6 study sessions (an eligibility assessment, a practice day, and 4 test sessions).
At each of four test sessions, participants will undergo one of these alcohol and cannabis exposure conditions: 1) placebo alcohol and placebo cannabis; 2) intoxicating dose of alcohol and placebo cannabis; 3) placebo alcohol and active cannabis, and; 4) intoxicating dose of alcohol and active cannabis. The order of these conditions will be randomly assigned. Participants will complete the alcohol manipulation followed by the cannabis manipulation. The alcohol and cannabis exposure sessions will be separated by at least 72 hours.
Participants will be asked not to use cannabis for 72 hours and alcohol for 48 hours prior to attending CAMH.
In certain instances, the Qualified Investigator may ask a participant to return for re-screening, e.g. repeat of urine test or other assessments performed for eligibility assessment. Also, in case of unforeseen delays in scheduling study participation, the Qualified Investigator will determine if there is a need to ask a participant to repeat some assessments, e.g., physical examination.
20 studies on the registry are indexed under Psychomotor Disorders; 6 are open to participants now.
This study's enrollment of 49 is close to the median of 49 across 15 interventional studies indexed under Psychomotor Disorders.
Browse Psychomotor Disorders studies →Centre for Addiction and Mental Health is the lead sponsor of 327 studies on the registry; 51 are open to participants now.
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Exclusion Criteria:
Participant will drink an alcoholic beverage to obtain a target blood alcohol content of 0.08mg% and will smoke a delta 9 tetrahydrocannabinol (potency 12.5%) cigarette.
Drug: alcohol · Drug: delta 9 tetrahydrocannabinol
Participant will drink tonic water (capped with a minimal amount of alcohol to enhance alcohol cues) and will smoke a delta 9 tetrahydrocannabinol (potency 12.5%) cigarette.
Drug: placebo alcohol · Drug: delta 9 tetrahydrocannabinol
Participant will drink an alcoholic beverage to obtain a target blood alcohol content of 0.08mg% and will smoke a placebo delta 9 tetrahydrocannabinol (\< 0.03%) cigarette.
Drug: alcohol · Drug: placebo delta 9 tetrahydrocannabinol
Participant will drink tonic water (capped with a minimal amount of alcohol to enhance alcohol cues) and will smoke a placebo delta 9 tetrahydrocannabinol (\< 0.03%) cigarette.
Drug: placebo alcohol · Drug: placebo delta 9 tetrahydrocannabinol
A single oral administration of an alcoholic beverage mixed in a 1:3 ratio of alcohol to tonic water to obtain a target blood alcohol content of 0.08mg%.
Also known as: ethanol
A single oral administration of a beverage containing tonic water of the same volume as the alcoholic beverage.
Also known as: tonic water
A single cannabis cigarette (potency 12.5% delta 9 tetrahydrocannabinol) will be given to participants to smoke over a 10 minute period, ad libitum. If the cannabis cigarette is not smoked in its entirety, the remainder will be weighed to estimate dose.
Also known as: marijuana, cannabis sativa
A single placebo cannabis cigarette (\<0.03% delta 9 tetrahydrocannabinol) will be given to participants to smoke over a 10 minute period, ad libitum. If the placebo cannabis cigarette is not smoked in its entirety, the remainder will be weighed to estimate dose.
Psychomotor Impairment: Standard Deviation of Lateral Position
The driving simulator objectively measures changes in driving behavior after alcohol and/or cannabis exposure. Standard deviation of lateral position (SDLP) is a measure of lane control (higher SDLP indicates worse lane control).
Time frame: Alcohol exposure is Time 0. Cannabis exposure follows 15 minutes after Time 0. Driving simulation tests occur within 2 hours before and approximately 45 minutes after Time 0.
Psychomotor Impairment: Mean Speed
The driving simulator will objectively measure changes in driving behavior after alcohol and/or cannabis exposure. Mean speed during the driving scenarios is measured by the simulator.
Time frame: Alcohol exposure is Time 0. Cannabis exposure follows 15 minutes after Time 0. Driving simulation tests occur within 2 hours before and approximately 45 minutes after Time 0.
Psychomotor Impairment: Standard Deviation of Speed
The driving simulator will objectively measure changes in driving behavior after alcohol and/or cannabis exposure. The simulator also (in addition to mean speed) measures standard deviation of speed.
Time frame: Alcohol exposure is Time 0. Cannabis exposure follows 15 minutes after Time 0. Driving simulation tests occur within 2 hours before and approximately 45 minutes after Time 0.
Psychomotor Impairment: Maximum Speed
The driving simulator will objectively measure changes in driving behavior after alcohol and/or cannabis exposure. The simulator measures maximum speed over the duration of the scenarios.
Time frame: Alcohol exposure is Time 0. Cannabis exposure follows 15 minutes after Time 0. Driving simulation tests occur within 2 hours before and approximately 45 minutes after Time 0.]
Psychomotor Impairment: Brake Latency
The driving simulator objectively measures changes in driving behavior after alcohol and/or cannabis exposure. During specific reaction time scenarios, participants must stop as quickly as possible after certain visual cues. The brake latency variable is measured as the mean stop/reaction time in seconds after the visual cue is presented.
Time frame: Alcohol exposure is Time 0. Cannabis exposure follows 15 minutes after Time 0. Driving simulation tests occur at baseline and approximately 45 minutes after Time 0.
| Milestone | Participant Group |
|---|---|
| Started | 49 |
| Received placebo alcohol/placebo cannabis | 38 |
| Received active alcohol/placebo cannabis | 40 |
| Received placebo alcohol/active cannabis | 41 |
| Received active alcohol/active cannabis | 40 |
| Completed | 35 |
| Not completed | 14 |
The driving simulator objectively measures changes in driving behavior after alcohol and/or cannabis exposure. Standard deviation of lateral position (SDLP) is a measure of lane control (higher SDLP indicates worse lane control).
| meters | Participant Group |
|---|---|
| Post-Drug Single Task - Placebo alcohol/placebo cannabis | 0.30 ± 0.01 |
| Post-Drug Single Task - Active Alcohol/Placebo Cannabis | 0.32 ± 0.01 |
| Post-Drug Single Task - Placebo Alcohol/Active Cannabis | 0.33 ± 0.01 |
| Post-Drug Single Task - Active Alcohol/Active Cannabis | 0.28 ± 0.01 |
| Post-Drug Dual Task - Placebo Alcohol/Placebo Cannabis | 0.28 ± 0.01 |
| Post-Drug Dual Task - Active Alcohol/Placebo Cannabis | 0.33 ± 0.01 |
| Post-Drug Dual Task - Placebo Alcohol/Active Cannabis | 0.32 ± 0.02 |
| Post-Drug Dual Task Active Alcohol/Active Cannabis | 0.38 ± 0.02 |
The driving simulator will objectively measure changes in driving behavior after alcohol and/or cannabis exposure. Mean speed during the driving scenarios is measured by the simulator.
| km/h | Participant Group |
|---|---|
| Post-Drug Single Task - Placebo alcohol/placebo cannabis | 84.07 ± 0.84 |
| Post-Drug Single Task - Active Alcohol/Placebo Cannabis | 85.06 ± 1.38 |
| Post-Drug Single Task - Placebo Alcohol/Active Cannabis | 83.27 ± 0.78 |
| Post-Drug Single Task - Active Alcohol/Active Cannabis | 84.64 ± 1.82 |
| Post-Drug Dual Task - Placebo Alcohol/Placebo Cannabis | 83.23 ± 0.94 |
| Post-Drug Dual Task - Active Alcohol/Placebo Cannabis | 87.34 ± 2.10 |
| Post-Drug Dual Task - Placebo Alcohol/Active Cannabis | 83.45 ± 1.09 |
| Post-Drug Dual Task Active Alcohol/Active Cannabis | 85.25 ± 2.27 |
The driving simulator will objectively measure changes in driving behavior after alcohol and/or cannabis exposure. The simulator also (in addition to mean speed) measures standard deviation of speed.
| km/h | Participant Group |
|---|---|
| Post-Drug Single Task - Placebo alcohol/placebo cannabis | 4.72 ± 0.55 |
| Post-Drug Single Task - Active Alcohol/Placebo Cannabis | 5.80 ± 0.78 |
| Post-Drug Single Task - Placebo Alcohol/Active Cannabis | 4.37 ± 0.47 |
| Post-Drug Single Task - Active Alcohol/Active Cannabis | 4.81 ± 0.44 |
| Post-Drug Dual Task - Placebo Alcohol/Placebo Cannabis | 4.92 ± 0.29 |
| Post-Drug Dual Task - Active Alcohol/Placebo Cannabis | 6.38 ± 0.59 |
| Post-Drug Dual Task - Placebo Alcohol/Active Cannabis | 5.15 ± 0.36 |
| Post-Drug Dual Task Active Alcohol/Active Cannabis | 6.06 ± 0.39 |
The driving simulator will objectively measure changes in driving behavior after alcohol and/or cannabis exposure. The simulator measures maximum speed over the duration of the scenarios.
| km/h | Participant Group |
|---|---|
| Post-Drug Single Task - Placebo alcohol/placebo cannabis | 93.85 ± 3.01 |
| Post-Drug Single Task - Active Alcohol/Placebo Cannabis | 98.85 ± 3.02 |
| Post-Drug Single Task - Placebo Alcohol/Active Cannabis | 94.64 ± 1.65 |
| Post-Drug Single Task - Active Alcohol/Active Cannabis | 97.76 ± 2.41 |
| Post-Drug Dual Task - Placebo Alcohol/Placebo Cannabis | 95.84 ± 1.43 |
| Post-Drug Dual Task - Active Alcohol/Placebo Cannabis | 102.84 ± 2.91 |
| Post-Drug Dual Task - Placebo Alcohol/Active Cannabis | 97.04 ± 1.73 |
| Post-Drug Dual Task Active Alcohol/Active Cannabis | 101.08 ± 2.68 |
The driving simulator objectively measures changes in driving behavior after alcohol and/or cannabis exposure. During specific reaction time scenarios, participants must stop as quickly as possible after certain visual cues. The brake latency variable is measured as the mean stop/reaction time in seconds after the visual cue is presented.
| seconds | Participant Group |
|---|---|
| Post-Drug Placebo alcohol/placebo cannabis | 0.99 ± 0.03 |
| Post-Drug Active Alcohol/Placebo Cannabis | 1.04 ± 0.02 |
| Post-Drug - Placebo Alcohol/Active Cannabis | 0.99 ± 0.03 |
| Post-Drug - Active Alcohol/Active Cannabis | 1.04 ± 0.02 |
Collected over Collected from the first to the last testing session (i.e., approximately one month).. Non-serious events are listed at a 0% frequency threshold.
| Group | Deaths | Serious | Other |
|---|---|---|---|
| Active Alcohol/Active Cannabis | 0/40 (0%) | 0/40 (0%) | 13/40 (32.5%) |
| Placebo Alcohol/Active Cannabis | 0/41 (0%) | 0/41 (0%) | 6/41 (14.6%) |
| Active Alcohol/Placebo Cannabis | 0/40 (0%) | 0/40 (0%) | 7/40 (17.5%) |
| Placebo Alcohol/Placebo Cannabis | 0/38 (0%) | 0/38 (0%) | 4/38 (10.5%) |
| Event | Active Alcohol/Active Cannabis | Placebo Alcohol/Active Cannabis | Active Alcohol/Placebo Cannabis | Placebo Alcohol/Placebo Cannabis |
|---|---|---|---|---|
| Nausea/VomitingGastrointestinal disorders | 3/40 | 0/41 | 5/40 | 2/38 |
| Common cold symptomsInfections and infestations | 3/40 | 1/41 | 0/40 | 0/38 |
| HeadacheGeneral disorders | 2/40 | 0/41 | 0/40 | 0/38 |
| Pain/Bruising at site of blood drawSkin and subcutaneous tissue disorders | 1/40 | 2/41 | 0/40 | 1/38 |
| Dizziness/FaintnessGeneral disorders | 0/40 | 2/41 | 0/40 | 0/38 |
| Urinary tract infectionRenal and urinary disorders | 0/40 | 0/41 | 0/40 | 1/38 |
| Decreased appetiteMetabolism and nutrition disorders | 1/40 | 0/41 | 0/40 | 0/38 |
| Skin infection at site of blood drawSkin and subcutaneous tissue disorders | 1/40 | 0/41 | 0/40 | 0/38 |
| Shingles infectionSkin and subcutaneous tissue disorders | 0/40 | 0/41 | 1/40 | 0/38 |
| Finger fractureInjury, poisoning and procedural complications | 0/40 | 0/41 | 1/40 | 0/38 |
Reported n is for participants who completed all conditions. Two participants were excluded from analyses; one participant was removed due to a suspected breach of protocol (did not abstain from cannabis use for 72 h) and the other was removed for not following study personnel instruction.
| Age, Continuous(years) | Participant Group |
|---|---|
| Mean | 22.5 ± 2.5 |
| Sex: Female, Male(Participants) | Participant Group |
|---|---|
| Female | 12 |
| Male | 16 |
| Race/Ethnicity, Customized(Participants) | Participant Group |
|---|---|
| White European | 10 |
| East Asian | 3 |
| White North American | 7 |
| mixed heritage | 3 |
| Asian-South | 2 |
| Latin American | 2 |
| Asian-South East | 1 |
| Body Mass Index(kg/m2) | Participant Group |
|---|---|
| Mean | 24.5 ± 3.4 |
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Centre for Addiction and Mental Health