• Patrick Diedrich

Alcohol + THC + Driving = Research!

Updated: Nov 5

Behavioral scientists provide a glimpse of the effects of mind-altering substances on driving capabilities.

Scientific discovery often conjures images of thoughtful expressions, lab coats and safety glasses; however, learning about the processes of the mind often require a more unconventional approach. That is precisely what Dr. Michael G. Lenné and his colleagues from Monash University, Australia did to study how several commonly used substances affect a driver behind the wheel.

Many studies are available that discuss the effects alcohol or THC have on driving performance, and the consensus is that, the greater the amount, the greater the impairment. But the research team from Monash University decided to take this concept a step further and take a look at what happens to driving performance when both substances are introduced simultaneously. Additionally, driving experience was analyzed to determine if someone who has had more time on the road would perform better than someone with less. It should also be noted, that the Dr. Lenné and his team used a driving simulator and had obtained permission from the Monash University Standing Committee on Ethical Research involving Humans before conducting the experiment.

Three groups of participants were established: inexperienced, experienced and a placebo group. The inexperienced driver group was composed of twenty-two drivers between the ages of 18 and 22 who had less than two years of driving experience. Twenty-five experienced drivers between the ages of 25 and 40, who had been driving for at least seven years, made up the experienced group. Before participating, every driver had to agree to a physical and mental fitness evaluation, had to have previously used both alcohol and cannabis, and have no history of substance abuse. After meeting these requirements, the participants would be receive financial compensation of $300 for as many as nine experiment sessions following one practice session.

Once all of the participant selection was out of the way, the science could begin! Each participant was given a glass of orange juice containing a high, low or no dose of ethanol. Afterwards, they had to smoke two pre-rolled cannabis cigarettes which fell under one of three categories: placebo (two cigarettes without any THC content), low-dose (one cigarette containing THC, and one without), and high-dose (both cigarettes containing TCH). The intent was to have each participant perform the driving simulation under each combination of substance conditions over the course of the experiment, for a total of nine sessions.

The driving simulation was divided in to three stages tested the participants' ability to perform tasks while under the influence. One of the tasks was to maintain a forty meter gap between a simulated car they were following while the lead car varied its speed. During the second stage a new task was introduced. The participant had to push one of two buttons on the steering wheel corresponding to which side of the road they noticed a sign with a word displayed on it. If the sign was on the right side of the road, they pushed the right button, left side meant pressing the left button. They had to perform this task while still maintaining the headspace with the car they were following. Lastly, during stage three, they only had to notice the signs without following a car. Throughout all of these stages, the drivers were instructed to follow all legal driving protocols within the the simulated environment.

Getting paid to drink and use some of "papa's medicine" seems like a pretty sweet gig, but several of the participants--for reasons not clearly stated in the research paper--could not finish the full nine sessions. Only 33 of the original 47 participants made it through the chemically-altered gauntlet. That being said, there was still enough data to draw several conclusions.

<SPOILER ALERT> smoking cannabis cigarettes increased headspace and reduced response time when compared to the placebo group. It was unclear if the amount of alcohol influenced the tasks because the data collected had too much variation, which made it difficult to determine if there was a direct link between performing driving tasks and the combination of THC with alcohol consumption. Dr. Lenné and his research team suspect that if the amount of alcohol consumed is increased, there may be a more significant result when used in conjunction with THC. Which means there is still plenty of research to do in the realm of drugs and alcohol, for all you intrepid, psychedelic researchers out there!

Do you think this type of research is ethical? Is there anything you would do differently to get more significant results? Let us know your thoughts, concerns or opinions in the comment section bellow!

Link to the study:

Links to Photos:

References (APA):

Florida DUI Lawyer. (n.d.). Driving Under the Influence of Drugs | Florida DUI Lawyer. Trusted

DUI Lawyers/Attorneys in Florida. Retrieved November 4, 2020, from

Lawyers, A. I. (2020, July 20). What is Driving Under the Influence? ANTHEM INJURY LAWYERS.

Lenné, M. G., Dietze, P. M., Triggs, T. J., Walmsley, S., Murphy, B., & Redman, J. R. (2010). The

effects of cannabis and alcohol on simulated arterial driving: Influences of driving experience and task demand. Accident Analysis & Prevention, 42(3), 859–866.

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