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Worries About Stoned Drivers Are Overblown


Cop pipe

Marijuana Legalization Opponents Try To Use Scare Tactics To Win Votes

The main rally cry for marijuana legalization opponents right now, and often medical marijuana opponents as well, is that if marijuana were legalized there would be a dramatic increase in stoned drivers on the road. Dr. Bob DuPont, President of the Institute for Behavior and Health, says research proves “the terrible carnage out there on the roads caused by marijuana.” People like Dr. DuPont will pull out statistics of crashes and say that there was marijuana in the driver’s systems, and therefore marijuana was the sole cause of those crashes. This is but one example of how people are trying to skew statistics to make it sound like there is a ‘stoned driving epidemic’ as some opponents are calling it. The fact of the matter is, these claims are overblown.

As Paul Armentano writes for NORML, “Marijuana is the most common illicit substance consumed by persons who report driving after drug use.[10] Epidemiological research also indicates that cannabis is the most prevalent illicit drug detected in fatally injured drivers and motor vehicle crash victims.[11] Reasons for this fact are twofold. One, cannabis is by far the most widely used illicit drug among the US population, with nearly one out of two Americans admitting having tried it.[12] Two, marijuana is the most readily detectable illicit drug in toxicological tests.

“Marijuana’s primary psychoactive compound, THC, may accumulate and be detected in blood for several hours in occasional users; in some chronic users, THC may be present in blood for a period of days after past use,[13-15] long after any performance impairing effects have worn off.[16] In addition, non-psychoactive byproducts of cannabis, known as metabolites, may be detected in the urine of regular users for days or weeks after past use.[17] (Other common illicit substances, such as cocaine or methamphetamine, do not possess such long half-lives.)”

“Therefore, the substance’s prevalence in toxicological evaluations of US drivers does not necessarily indicate that it is a frequent or significant causal factor in auto accidents. In fact, states that have experienced a significant increase in the total number of authorized medical cannabis users have in general experienced no proportional corresponding rise in traffic fatalities, and most have experienced a decline in overall fatal accidents.”

Marijuana legalization opponents will state that marijuana decreases motor skills, and that somehow the debatable amount of change in motor skills will almost certainly lead to a 24 car pileup daily. But once again, these claims are overblown, and once again, I quote the legendary marijuana human encyclopedia Paul Armentano from NORML, “According to one review of the literature: “The risk of all drug-positive drivers compared to drug-free drivers is similar to drivers with a blood alcohol concentration of 0.05%. The risk is also similar to drivers above age 60 compared to younger drivers [around age 35].””

“While it is well established that alcohol consumption increases accident risk, evidence of marijuana’s culpability in on-road driving accidents and injury is far less clear. Although acute cannabis intoxication following inhalation has been shown to mildly impair psychomotor skills, this impairment is seldom severe or long lasting.[19-20] (By contrast, virtually no published research exists assessing the oral ingestion of cannabis edibles on psychomotor performance). In closed course and driving simulator studies, marijuana’s acute effects on psychomotor performance include minor impairments in tracking (eye movement control) and reaction time (break latency), as well as variation in lateral positioning (weaving), headway (drivers under the influence of cannabis tend to follow less closely to the vehicle in front of them), and speed (drivers tend to decrease speed following cannabis inhalation).[21]

“Notably, these impairments in performance are more likely to be manifested in driver simulator tests than in assessments of actual on-road behavior, where changes in performance are consistently nominal.[22]For example, A 2001 study evaluating the impact of marijuana intoxication on driving proficiency on city streets among sixteen subjects reported essentially no differences in subjects’ driving performance after cannabis administration, concluding: “Performance as rated on the Driving Proficiency Scale did not differ between treatments. It was concluded that the effects of low doses of THC … on higher-level driving skills as measured in the present study are minimal.”[23] Similarly, a 1993 trial funded by the United States National Highway Traffic Association (NTHSA) evaluated subjects’ driving performance after cannabis inhalation in high-density urban traffic. Investigators reported, “Marijuana … did not significantly change mean driving performance.”[24]

“In general, cannabis-induced variations in driving behavior, when present, are less consistent or pronounced than the impairments exhibited by subjects under the influence of alcohol.[25] Unlike subjects impaired by alcohol, individuals under the influence of cannabis tend to be aware of their impairment and try to compensate for it accordingly, either by driving more cautiously[26] or by expressing an unwillingness to drive altogether.[27] Further, numerous studies report that experienced cannabis users develop tolerance to many of the changes in cognitive or psychomotor performance associated with acute cannabis intoxication.[28-30]

“Most recently, a 2010 double-blind, placebo-controlled study of 21 heavy cannabis users assessed the impact of alcohol or THC inhalation on measures of perceptual motor control (critical tracking task), dual task processing (divided-attention task), motor inhibition (stop-signal task), and cognition (Tower of London). Authors reported: “Alcohol significantly impaired critical tracking, divided attention, and stop-signal performance. THC generally did not affect task performance.” They concluded, “[T]he present study generally confirms that heavy cannabis users develop tolerance to the impairing effects of THC on neurocognitive task performance.”[31]

“As a result, cannabis-induced variations in performance do not typically appear to play a significant role in on-road traffic accidents when the THC levels present in a driver’s blood are low and/or cannabis is not consumed in combination with alcohol.[32-33] For example, a 1993 National Highway Traffic Safety Administration review of the role of drug use in fatal accidents reported, “[T]here is little if any evidence to indicate that drivers who have used marijuana alone are any more likely to cause serious accidents than drug free drivers.”[34]

“A more recent assessment by Blows and colleagues noted that self-reported recent use of cannabis (within three hours of driving) was not significantly associated with car crash injury after investigators controlled for specific cofounders (e.g., seat-belt use, sleepiness, etc.)[35] A 2004 observational case control study published in the journal Accident, Analysis and Preventionreported that only drivers under the influence of alcohol or benzodiazepines experience an increased crash risk compared to drug-free controls. Investigators did observe increased risks — though they were not statistically significant — among drivers using amphetamines, cocaine and opiates, but found, “No increased risk for road trauma was found for drivers exposed to cannabis.”[36]

“A limited number of more recent studies and reviews have postulated a positive association between presumed recent, dose-dependent cannabis exposure and a gradually increased risk of vehicle accident.[37-39] However, this elevated risk was below the risk associated with drivers who had consumed even small quantities of alcohol.”

“A 2007 case-control study published in the Canadian Journal of Public Health reviewed 10-years of US auto-fatality data. Investigators found that US drivers with blood alcohol levels of 0.05% — a level well below the legal limit for intoxication — were three times as likely to have engaged in unsafe driving activities prior to a fatal crash as compared to individuals who tested positive for marijuana.[40] A 2005 review of auto accident fatality data from France reported similar results, finding that drivers who tested positive for any amount of alcohol had a four times greater risk of having a fatal accident than did drivers who tested positive for marijuana in their blood.[41] In the latter study, even drivers with low levels of alcohol present in their blood (below 0.05%) experienced a greater elevated risk as compared to drivers who tested positive for higher concentrations of cannabis (above 5ng/ml). Both studies noted that overall few traffic accidents appeared to be attributed to driver’s operating a vehicle while impaired by cannabis.”

“Following the publication of these papers, various investigators have attempted to associate specific THC blood levels to driver impairment.[42-43] However, there are many reasons why such an association should be interpreted with extreme caution. First, peak THC blood levels following inhalation do not consistently correspond with levels of peak impairment.[44] (In fact, subjects who inhale THC typically ascertain their highest THC blood levels within minutes, well before the drug’s impairing effects have reached their peak.) As a result, it is virtually impossible to make inferences regarding a subject’s impairment based upon the presence of THC alone in a single sample.[45-46]

“Second, cannabis’ effect on psychomotor performance varies widely among individual subjects, particularly among those who are cannabis experienced versus those who are naive. As a result of these extreme variations, even experts who are on record in support of estimated blood/THC impairment standards acknowledge that such thresholds “are not necessarily applicable to each and every driver an individual.”[47]

“Third, recent studies of chronic cannabis consumers indicate that residual levels of THC may be present in blood without associated impairment of performance for several days after past use.[48-49] This accumulation of THC in chronic consumers “leads to cannabinoid concentrations in sober phases that resemble concentrations found in occasional users after acute cannabis use,”[50] thus making the universal application of a specific blood/THC impairment standard inappropriate.”

“Finally, at this time there is no practical method for law enforcement officers at the scene to collect blood samples from suspected DUI cannabis drivers in a timely manner. This delay in collection (which may typically be as long as several hours), combined with the THC’s complex and inconsistent pharmacokinetics, make it impossible to infer whether, or to what extent, a subject was previously impaired based solely on a positive blood test result.[51]

Marijuana legalization opponents will claim that there needs to be a zero tolerance stance on marijuana and driving, or a very low level, until there is a scientific ‘one size fits all’ test like alcohol to prove impairment. That argument is also bogus. Once again, Paul Armentano from NORML, “increased efforts should be made within the law enforcement community to train officers and DREs (drug recognition experts) to better identify drivers who may be operating a vehicle while impaired by marijuana. Changes may also be adopted to roadside Standardized Field Sobriety Test making these evaluations more sensitive to drivers who may be under the influence of cannabis. Preliminary scientific evaluations of these tests in controlled conditions have shown that subjects’ performance during modified SFSTs may be positively associated with dose-related levels of marijuana impairment.[61]

I would make the argument that there will not even be any increase in stoned drivers. I have never met a marijuana consumer that has stated, ‘You know what, I don’t drive after smoking marijuana right now. But the second it becomes legal, I am totally going to get baked and drive all over the place.’ When I get really high, the last thing that I want to do is drive somewhere. Isn’t that why they invented pizza delivery?? Responsible marijuana consumers don’t get stoned and drive. When marijuana becomes legal, the same irresponsible people will be stoned drivers, and the vast majority of us that consume marijuana responsibly will continue to do so.

Marijuana legalization supporters in Washington, in an attempt to make their initiative more swing voter friendly, placed a provision in their initiative that defines a blood level limit. “Voters were very concerned about impaired driving,” said Alison Holcomb, campaign director for Washington’s legalization measure. Unfortunately, it looks like 2012 might become a missed opportunity in Washington due to backlash from otherwise sympathetic marijuana reform supporters. I know Washington residents like Steve Sarich and Miggy420 have spoken out quite a bit on TWB about the issue. I think that there needs to be a distinction made between ‘present in the driver’s system’ and ‘impaired’ because they are often two totally different things. We pay cops to do their jobs, which last time I checked, was knowing when someone was not safe to be driving on public roads. When did that stop being good enough?


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