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The dominant paradigm for cannabis impairment assessment by the roadside and in the workplace is drug testing. This is a problem since drug testing frequently does not measure impairment, just the chemicals that remain in the body after drug use.
There is no cannabis equivalent to the alcohol “breathalyzer,” since alcohol and THC behave differently in the body. THC metabolites can remain at high levels in the body long after any psychoactive effects have passed. This is a problem, particularly for medical cannabis patients, as there is no accepted way for them to assess their own impairment other than subjectively.
The slogan, “If you feel different, you drive different,” is not helpful, since alcohol and cannabis research show that people can, and do, underestimate their level of impairment. If medical cannabis patients choose to drive, they are risking a DUI from a blood or saliva test that shows they used cannabis in the past, even if they are no longer impaired.
The Problem with Bodily Fluids for Cannabis Impairment Assessment
One of the primary problems with tools like blood and saliva testing for cannabis impairment assessment is that they ignore the tolerance effects that frequent cannabis consumers, like medical cannabis patients, can develop. Proponents of these tests argue that THC use in saliva can be detected for up to 30 minutes, which they observe is the time most likely to show impairment. But that assumes cannabis is always causing impairment when it doesn’t because of tolerance. With respect to driving, cannabis patients being held to a higher standard of impairment than are alcohol consumers is discriminatory.
Fortunately, a software-driven, paradigm-shifting alternative has emerged, an app called Druid from Impairment Science, Inc. Developed by a cannabis consumer, the Druid app assesses cognitive-motor impairment by measuring cognitive-motor behavior (e.g., reaction time, hand-eye coordination, balance) in either one or three minutes. The app enables individuals to test their own impairment.
Druid has been validated in several published peer-reviewed studies. In a study at Johns Hopkins Medical School, researchers found Druid to be the most sensitive measure of impairment of the many available to them. The study’s participants came to the lab on 6 different occasions. They were asked to either eat a brownie or use a Volcano® vaporizer, each mode of consumption with varying levels of THC. The researchers found that Druid could distinguish different levels of impairment from different amounts of THC consumed. No other tool can do this.
A second study found that Druid could identify impairment or lack of impairment in two samples of frequent consumers of cannabis, mostly medical cannabis patients. One and a half hours after consuming their typical dose, the average baseline of both samples returned to the initial baselines.
Reflecting the fact that Druid can identify impairment from any source, a third study found Druid able to identify impairment in a sample of volunteers at Massachusetts police academy “wet labs.” Wet labs are part of the recruits’ Standard Field Sobriety Test (SFST) training. Volunteers consume alcohol until their blood alcohol concentration (BAC) reaches 0.11% or so. The cadets can then practice the SFST on intoxicated people. An additional paper, currently under editorial review, reports that Druid can track impairment caused by concussion, as well as the subsequent recovery from concussion.
How the Druid app works differently for cannabis impairment assessment
Grounded in cognitive neuroscience, the Druid app presents several video game-like tasks that measure reaction time, hand-eye coordination, time estimation, decision-making, and balance. The app then integrates hundreds of measurements into a single impairment score, ranging from 25 to 75, with a higher number indicating higher impairment. For anyone under age 50, a score of 55 is the approximate equivalent impairment to a 0.08% blood alcohol concentration. Using Druid, individuals create an unimpaired baseline and can then measure by what degree taking their medication increases their impairment, if at all.
Get the App
Druid has the potential to make substantial contributions to medical cannabis treatment, enabling patients and their doctors to find the best dose that treats the symptoms with the lowest amount of impairment. Impairment Science, Inc. has also developed Druid Enterprise, a cloud-based Druid score database and management portal that enables doctors to assess the efficacy of treatment by reviewing their patients’ Druid scores. (This is the link to an interview/podcast that Dr. Milburn did with Dr. Benjamin Caplan of the CED Clinic for cannabis education about how Druid can be used by medical cannabis patients and their doctors.)
The development of tolerance to cannabis has been widely documented (e.g., Mendelson et al., 1976; Haney, Ward, Comer, Foltin, & Fischman, 1999; Kirk & de Wit, 1999; Nowland & Cohen, 1977), although not without findings of no tolerance. Whether a person’s frequent use of cannabis has produced tolerance or not, e.g., if they are a medical cannabis patient, has been raised as an issue with the legalization of medical cannabis and adult-use cannabis. Most experimental performance studies to date have been conducted on occasional users of cannabis with a low frequency of lifetime use. It has been suggested that performance impairment during cannabis intoxication is lower in frequent cannabis users as a consequence of tolerance.
The data presented here show the effects of using cannabis after taking a break to restore the reactivity of the CB1 receptors. All the data are from a single daily cannabis user who agreed to take breaks of varying lengths from using cannabis.
The blue curve (the “Tolerance Curve”) is the person’s reactivity over time to vaporizing .5 gm of cannabis following daily use, but before taking a cannabis break of varying lengths, i.e., T-breaks of 1 day, 2 days, 3 days, 6 days, and 2 1/2 weeks. They all showed the same pattern as above: much higher reactivity the day consuming after the break, and then declining reactivity on each day of daily use, and after 3-4 days, returning to the level of the “tolerance curve.”
If one consumes cannabis every day, one will likely be increasing cannabis tolerance, and the longer the daily consumption, the greater the increase. This lowers the level of high one can reach. Taking short breaks do not appear to restore previous reactivity except in the short term. Impairment Science is currently researching what consumption pattern, e.g., every other day, every third day, etc., will maintain reactivity at the same level or will start decreasing tolerance.
Additional: Health Europa Paper
Link to the “How to use Druid for medical cannabis patients” podcast that I did with Dr. Caplan: