Driving, Drinking, and Drug Use

11. Comparison of Results from Standardized Field Sobriety Tests (SFST) and Roadside Saliva Drug Tests in Detecting Cannabis Use

"The SFST was mildly sensitive to the effects of cannabis alone. A dose of 400 ?g/kg body weight THC significantly increased the percentage of participants displaying impairments in OLS compared to baseline performance from 21 to 50 %. THC also increased percentage of individuals showing impairment on HGN from 0 to 15 %, relative to baseline, but this change only approached statistical significance. WAT [Walk And Turn] and the overall score on SFST did not discriminate between THC and baseline. These findings appear in line with previous studies that have reported a relation between impairment on the SFST and presence of THC in blood. A study that assessed which signs of the Drug Evaluation and Classification evaluations predicted various drug categories (including cannabis) at best showed that OLS [One-Leg Stand] contributed significantly to the prediction, but HGN [Horizontal Gaze Nystagmus] and WAT did not (Porath-Waller et al. 2009). Papafotiou et al. (2005a) assessed SFST performance in 40 healthy participants who received low and high doses of THC in a placebo-controlled study. On average, blood THC concentrations obtained after the highest dose were comparable to serum THC concentrations achieved in the present study after smoking cannabis. Yet, THC significantly affected performance on OLS, HGN, and WAT and appeared to be more prominent as compared to the current study. For example, in that study THC produced impairments on overall SFST performance in up to 50 % of the participants (Papafotiou et al. 2005a) but in only 30 % of the participants of the present study. These differences may be explained in terms of differences in cannabis use history. In the study by Papafotiou et al. (2005a), the reported frequency of cannabis use of the participants varied from once a week to once every 2–6 months. The present study however only included heavy cannabis users, who smoked cannabis on at least four occasions per week. Previous studies demonstrated that heavy cannabis users develop tolerance to the impairing effects of THC on neurocognitive measures (Hart et al. 2001; Ramaekers et al. 2011). It is likely that many of the participants who participated in the present study, in part or in total, developed tolerance to the impairing effects of THC as well. In such a scenario, the failure of the SFST to demonstrate robust effects of THC is not necessarily an indicator of poor sensitivity, but may reflect the chronic cannabis use of the participants."

Bosker, W.M., et al., "A Placebo-Controlled Study to Assess Standardized Field Sobriety Tests Performance During Alcohol and Cannabis Intoxication in Heavy Cannabis Users and Accuracy of Point of Collection Testing Devices for Detecting THC in Oral Fluid," Psychopharmacology (2012) 223:439-446.

12. Medical Marijuana Laws Associated With Reduction in Traffic Fatalities

"Using population-based data from 1985 to 2014, we found that, first, states that enacted MMLs during the study period had lower fatality rates compared with states without MMLs. Second, on average, traffic fatalities further decreased in states post-MML, with both immediate (sudden change in fatality rate after MML enactment) and gradual (change in rate trend after MML enactment) declines over time in those aged 25 to 44 years. Third, the association between MML and traffic fatalities varied considerably across states. Fourth, the presence of operational dispensaries was also associated with reductions in traffic fatalities in those aged 25 to 44 years.
"We found that, on average during the study period, MML states had lower traffic fatality rates than non-MML states. It is possible that this is related to lower levels of alcohol-impaired driving behavior in MML states. Evidence from the Behavioral Risk Factor Surveillance Systems data from 200027 and 201228 shows that states that have enacted MMLs, compared with non-MML states, had, on average, lower proportions or rates of drivers endorsing having driven after having too much to drink. In addition, other unmeasured characteristics, including strength of public health laws related to driving, infrastructure characteristics (e.g., high-technology roads), or quality of health care systems, may partially explain these findings."

Julian Santaella-Tenorio, Christine M. Mauro, Melanie M. Wall, June H. Kim, Magdalena Cerdá, Katherine M. Keyes, Deborah S. Hasin, Sandro Galea, and Silvia S. Martins. US Traffic Fatalities, 1985–2014, and Their Relationship to Medical Marijuana Laws. American Journal of Public Health: February 2017, Vol. 107, No. 2, pp. 336-342.
doi: 10.2105/AJPH.2016.303577

13. Prevalence of Driving Under the Influence of Alcohol in the US

"The NRS [National Roadside Survey] surveys reveal a decreasing trend in alcohol use from the first survey in 1973 to the most recent one in 2013–2014. Figure 1 shows the percentage of weekend nighttime drivers with BrACs across three categories: BrAC of .005 to .049 g/210 L; 2 BrACs of .050 to .079; and BrACs of .080 and higher. The surveys found a decline in each BrAC category. Further, there has been a large decrease in the percentage of drivers who were alcohol positive, from 35.9 percent in 1973 to 8.3 percent in 2013–2014. For BrACs of .08 and higher, there was a decrease from 7.5 percent in 1973 to 1.5 percent in 2013–2014, revealing an impressive 80 percent reduction in the percentage of alcohol-impaired drivers on the road on weekend nights. Also of importance is the decrease from 6.1 percent to 1.6 percent from 1973 to 2013–2014 for BrACs of .050 to .079 category."

Berning, A., Compton, R., & Wochinger, K. (2015, February). Results of the 2013–2014 National Roadside Survey of alcohol and drug use by drivers. (Traffic Safety Facts Research Note. Report No. DOT HS 812 118). Washington, DC: National Highway Traffic Safety Administration.

14. Estimated Prevalence Of Substance Use Among Drivers In Fatal Auto Accidents

"Overall, 23,591 (90.9%) of the 25,951 drivers who died within 1 hour of a crash in these 6 states underwent toxicological testing. Drivers who were tested for drugs were similar in crash circumstances to those who were not tested, but they appeared to be slightly younger (mean age = 39.4 (standard deviation, 19.4) years vs. 43.4 (standard deviation, 27.7) years), more likely to be male (77.7% vs. 75.8%), more likely to be involved in nighttime crashes (51.4% vs. 47.0%), and more likely to have been involved in a crash in the previous 3 years (15.7% vs. 13.9%) than those who were not tested.
"Of the 23,591 drivers tested, 39.7% were positive for alcohol, and 24.8% tested positive for other drugs. The prevalence of alcohol involvement was stable at approximately 39% from 1999 to 2010 (Z = ?1.4, P = 0.16). Alcohol involvement was more prevalent in men (43.6%) than in women (26.1%), but trends were stable for both sexes (Table 1). In contrast, the prevalence of nonalcohol drugs showed a statistically significant increasing trend over the study period, rising from 16.6% (95% confidence interval (CI): 14.8, 18.4) in 1999 to 28.3% (95% CI: 26.0, 30.7) in 2010 (Z = ?10.19, P < 0.0001). The prevalence rates of non-alcohol drugs and 2 or more nonalcohol drugs increased significantly over the study period in both sexes (Table 1). The prevalence of nonalcohol drug use increased significantly across all age groups (Figure 1)."

Joanne E. Brady and Guohua Li. "Trends in Alcohol and Other Drugs Detected in Fatally Injured Drivers in the United States, 1999–2010." American Journal of Epidemiology. (2014) 179 (6): 692-699. doi: 10.1093/aje/kwt327.

15. Prevalence of Use of Other Drugs by Drivers in the US, 2013

"The 2013–2014 study examined the use of drugs, focusing on drugs with the potential to impair driving skills, including over-the-counter, prescription, and illegal drugs. Participants were asked to provide an oral fluid and blood sample in addition to a breath sample. The oral fluid and blood samples were tested for the presence of a large number of potentially impairing drugs including cannabinoids, stimulants, sedatives, antidepressants, and narcotic analgesics. Not all drivers provided both an oral fluid and blood sample; some drivers provided just one sample but many provided both.
"The reader is cautioned that drug presence does not necessarily imply impairment. For many drug substances, drug presence can be detected after impairment that might affect driving has passed. For example, traces of marijuana use can be detected in blood samples several weeks after heavy chronic users stop ingestion. In this study, for marijuana, we tested only for THC (delta 9 tetrahydrocannabinol), the psychoactive substance in marijuana, and 11-OH-THC, its active metabolite. When marijuana is smoked or ingested, THC is absorbed into the blood stream and is distributed into areas of the body, including the brain. There are over 100 marijuana metabolites detectable in blood that research has not associated with the psychoactive effects of marijuana use. Whereas the impairment effects for various concentration levels of alcohol in the blood or breath are well understood, there is little evidence available to link concentrations of other drugs to driver performance."

Berning, A., Compton, R., & Wochinger, K. (2015, February). Results of the 2013–2014 National Roadside Survey of alcohol and drug use by drivers. (Traffic Safety Facts Research Note. Report No. DOT HS 812 118). Washington, DC: National Highway Traffic Safety Administration.