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Driving Simulation Technology Being Used to Measure Impairment Related to Cannabis 

Cannabis and driving

A Leading Researcher Provides Insight

Since our inception, there has been one guiding force behind everything that we do at Systems Technology Inc., … safety.  

It’s a mantra first stated by our founders, Irving L. Ashkenas and Duane T. McRuer, over 65 years ago, and one that we still live by today, especially with our simulation technologies that emulate parachuting and automobile driving.  

The STISIM Drive suite of products, contributes to safe driving in its support of research, clinical therapy, and driver assessment.  The STISIM Drive® Clinical Application provides therapy professionals with a powerful tool for assessing patient deficits, and to return them to driving; and The STISIM Drive® Research Suite supports academic research in evaluating effects of driver impairment caused by various substances.  

We all probably instantly think of alcohol when thinking of driving impairment, which is certainly something our technology has been used to study. However, a growing area of interest is in better understanding the impact of cannabis on driving ability. 

To better understand this interesting field of study, and how driving simulation technology contributes to it, we posed a few questions to a prominent researcher that utilizes STISIM Drive in their studies – Dr. Thomas Marcotte, Professor of Psychiatry at the University of California, San Diego; and Co-Director of their Center for Medicinal Cannabis Research.  

Center for Medicinal Cannabis Research
The Center for Medicinal Cannabis Research (CMCR) at UC San Diego. Photo: CMCR

How did you come to have an interest in cannabis research?  

As a neuropsychologist, my career began with a focus on the effects that HIV-related brain changes have on everyday functioning, including driving performance. A few years into my involvement with the HIV Neurobehavioral Research Program at UCSD, we were awarded State funding to develop the Center for Medicinal Cannabis Research (Igor Grant, MD, Director). I was very interested in expanding my research to include the effects that cannabis might have on both cognition and driving abilities. My career-long interest in this topic is a result of the complexities of cannabis use – it may be beneficial for some medical conditions, yet it can cause impairment. However, not everyone who uses it becomes significantly impaired. 

What else can you tell us about the Center for Medicinal Cannabis Research? 

Our Center was founded in 2000, funded by the California State Legislature in order to generate rigorous studies regarding the benefits, and limitations, of cannabis as medicine. We have subsequently conducted or supported numerous clinical trials for a variety of medical and psychiatric conditions. These studies have been funded by the state, NIH, and philanthropy. We also provide funding for investigators at other California research institutions conducting cannabis research, using a robust peer-reviewed approach to selecting projects. We currently have over 20 CMCR-affiliated projects. 

What are the basic findings on cannabis and driving impairment produced through your research thus far?  

In the largest study of its type (n = 191), we found that THC exposure does indeed cause impairment with respect to driving performance – but not all individuals did significantly worse after smoking. About 45% would be considered “impaired” compared to the placebo group. For this study participants were to smoke ad libitum – “as you would at home to get high”. While more experienced users smoked in a manner that resulted in higher THC concentrations in their blood, they did no worse than the less experienced groups who had significantly lower THC concentrations. This suggests that they developed behavioral tolerance to the effects of THC. However, they also did no better on the simulations – they counteracted this tolerance by getting more THC into their system. In addition, we had groups smoke lower (5.9% THC) and higher THC (13.4%) content cigarettes. When told to smoke to achieve their desired level of highness, they ended up with similar THC blood concentrations and similar simulator performance. So they “self-titrated” in how they smoked – the content of the cigarette itself had little impact. Lastly, the effects of smoked THC lasted 3.5 to 4.5h. 

Is cannabis impairment on par with alcohol?  

This is difficult to address. We have yet to conduct alcohol studies using these simulations, although those are in process. While others have reported that the effects of THC are in the range of a BAC of .05%, this obviously depends upon the amount smoked or ingested. In addition, studies frequently examine standard deviation of lateral position (SDLP; or “swerving”). However, while this is a very useful driving metric, it may be other factors associated with alcohol use, such as increased risk taking, that result in dangerous driving. These behaviors are less frequently seen with cannabis-related driving impairments, at least at the group level. 

Why do you use driving simulation tools in your studies?   

Simulation provides some key benefits compared to on-road evaluations – the ability to 1) put individuals into challenging situations that are not feasible to do in the field (for safety and ethical reasons), 2) replicate the same, standard challenges for each participant, and 3) create similar challenges during different simulation runs, without them appearing to be the same. 

Are there any upcoming studies/research that you can share some basic details about?  

In the coming year we will be using driving simulations to examine unobtrusive methods for identifying individuals under the influences of alcohol, as well as a project exploring the effects of highly concentrated THC products and related administration methods, such as vaping and dabbing, on driving performance. 

With legal cannabis usage now the norm across the United States and many other countries, we are certain to see far more interest in measuring its impact on impaired driving. STISIM Drive will continue to be a leading technology used to assist scientists in collecting and analyzing the data they need to contribute to the body of research that will lead to improved safety. Which is what it’s all about! 

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