In the past, the National Institute on Drug Abuse has been looked at by marijuana proponents as a misled organization that was partly created to keep cannabis from becoming a legitimate medical benefit. Their studies were legendary for being negative and also involving a very small group of people, which really kept the true scope of any factual evidence from ever being proven. NIDA’s latest study, while still involving a small group of people and still being a bit critical, doesn’t come down as harshly on marijuana as in past research, at least when it comes to comparing the effects of driving stoned to driving drunk.
According to an article in Time, the most recent national roadside survey from the National Highway Traffic Safety Administration found that over 8 percent of weekend nighttime drivers had some alcohol in their system, while almost 13 percent tested positive for THC. That’s up almost 9 percent from 2007.
The NIDA study looked at 18 occasional cannabis smokers, 13 of them men, between the ages 21 and 37. They took six 45-minute drives in a driving simulator while testing a different combination of high or low concentration THC, alcohol, and placebos (the placebos were fruit juice with alcohol swabbed in the rim, topped off with 1ml alcohol, all to simulate alcohol’s smell and taste).
The researchers looked at weaving within the lane, the number of times the car left the lane and the speed of the weaving. Alcohol had an effect on the number of times the car left the lane and the speed of the weaving, but marijuana did not. There was an increase in weaving with marijuana users. Drivers with blood concentrations of 13.1 ug/L THC were seen weaving similarly to the weaving a driver would make if he had a .08 breath alcohol concentration, the legal limit in most states. To get a scope of THC levels, 13.1 ug/L THC is more than twice the 5 ug/L limit in Washington and Colorado.
One of the main researchers in the study pointed out that it was important to realize that this study looked at the “concentration of THC in the driver’s system while they were driving. That’s different from the concentration that’s usually measured in a drugged driver out on the road, whose blood might not get checked until hours after an arrest. That length of time usually leads to a big drop in the THC level from the time they were driving. Because of that, researchers are looking at ways to estimate how long it takes THC concentrations in the blood to drop. One researcher also recommended that the 5 ug/L limit isn’t strict enough, especially for people who have a low tolerance to cannabis.
The study also went on to find that pot and alcohol have more of an impact on driving when they are used together. Drivers who used both weaved within lanes, even if their blood THC and alcohol concentrations were below the threshold for impairment if they were taken on their own. Smoking pot while drinking a little alcohol also increased the effects of THC and made the high a lot stronger. Also, THC delayed the peak of alcohol impairment, meaning that it took longer for someone using both to feel drunk.