Driving Impairment Research:

Laboratory research and on-the-road studies have both established that consuming THC directly impairs driving and related behaviors and cognitions. Consuming marijuana increases the risk of accidents while driving, and this risk is dose-dependent, such that higher levels of THC in the blood are associated with higher risk (Hartman & Huestis, 2013).  There are multiple well-controlled studies documenting impairment both directly on driving skill/behavior and on key executive functions that are involved in driving behavior (attention, reaction time, impulsivity).  While some researchers have suggested that the driving of habitual users is less affected by marijuana than infrequent users (e.g., Sewell et al., 2009); many other researchers disagree, suggesting that attempts to compensate are mostly ineffective (Metrik, 2016).   So, if you have used marijuana or other drugs, you should not choose to drive until your DRUID score gets close to your baseline, within approximately 5%.

Research has shown that after consuming alcohol, impairment begins on the average at a Blood Alcohol Concentration (BAC) of .04—considerably below the legal limit of a BAC of .08 or above.  Impairment following the use of marijuana can last longer than three hours, particularly if the person has used alcohol as well (Hartman et al., 2016).  Even just one glass of wine or beer, in addition to marijuana, can have this effect.  Research shows that consuming both alcohol and marijuana heightens the level of impairment considerably more than using just one or the other.  This is because these two drugs disable two different cognitive systems (Sewell, Poling & Sofuoglu, 2009), hindering a stoned driver’s compensatory efforts.

Research Using DRUID:

DRUID is currently being tested in a NIH-funded study at the Brown University Medical School.  We do have these less formal results: These DRUID results show the level of impairment over time, with and without alcohol:

The person’s DRUID impairment score goes below the level where impairment begins after about 3 hours.

However, observe what happens when alcohol is combined with marijuana:

The DRUID impairment scores indicate that the person’s level of impairment had approached safe levels, but then just one glass of wine increased impairment to a level of slowed reaction times and impaired judgment, making driving more dangerous.

Future Benefits DRUID Will Provide:

Our research indicates that different strains of marijuana have different patterns of impairment over time that are not linear.  That is, impairment does not simply go up and then down over time; it might go up, be level for a while, then increase again before it decreases.  As we collect more data, we plan to provide users with DRUID profiles of various strains of marijuana. 

The DRUID impairment scores indicate that the person’s level of impairment had approached safe levels, but then just one glass of wine increased impairment to a level of slowed reaction times and impaired judgment, making driving more dangerous.

Future Benefits DRUID Will Provide:

Our research indicates that different strains of marijuana have different patterns of impairment over time that are not linear.  That is, impairment does not simply go up and then down over time; it might go up, be level for a while, then increase again before it decreases.  As we collect more data, we plan to provide users with DRUID profiles of various strains of marijuana. 

Learn More Here:

Measuring drug impairment in drivers is easier said than done

Cannabis in Colorado: more than you ever wanted to know

How can you tell if a driver is stoned?

Marijuana sobriety test

What stoned driving looks like and how California might regulate it

The difficulty of enforcing laws against driving while high

References

  • Ballesteros, S., ,Prieto, A., Mayas, J., ,Toril, P., Pita, C., de León, L. P., Reales, J. M., Waterworth, J. (2014).Brain training with non-action video games enhances aspects of cognition in older adults: A randomized controlled trial. Frontiers in Aging Neuroscience, 6:1-14.
  • Hartman, R. L., Brown, T. L., Milavetz, G., Spurgin, A., Pierce, R. S., Gorelick, D. A., Gaffney, G., & Huestis, M.A.  (2016). Cannabis effects on driving longitudinal control with and without alcohol.  Journal of Applied Toxicology (online).
  • Hartman, R. L., & Huestis, M. A.  (2013). Cannabis effects on driving skills. Clinical Chemistry, 59(3):478–492. 
  • Mack, D. J., Ilg, U. J.  (2014).  The effects of video game play on the characteristics of saccadic eye movements.  Vision Research, 102:26-32.
  • NHTSA (2016)
  •  Seçer, I., & Satyen, L., (2014).  Video game training and reaction time skills among older adults.  Activities, Adaptation & Aging, 38(3), 220-236.
  • Sewell, R. A., Poling, J., & Sofuoglu, M.  (2009). The effect of cannabis compared with alcohol on driving.  American Journal of Addiction, 18: 185-193.
  • Stroud, M. J., & Whitbourne, S. K., (2015). Casual video games as training tools for attentional processes in everyday life. Cyberpsychology, Behavior, and Social Networking, Vol 18(11), Nov,. pp. 654-660 
  • Toril, P., Reales, J. M., & Ballesteros, S., (2014).  Video game training enhances cognition of older adults: A meta-analytic study.  Psychology and Aging, Vol 29(3), 706-716.
  • Metrik, J. (2016).  Brown University Medical School, Department of Psychiatry.  Personal Communication.