People Against Drink/Drug Driving

As pot usage surges, sensible regulation is lagging behind

Cannabis-related traffic fatalities are a threat to public safety. Governments need to get serious.

Marijuana legalization is killing a lot of people. Not slowly — though some studies suggest that it may be doing that, too — but quickly, in car crashes. It’s one more symptom of the disastrous rush by lawmakers to capitalize on cannabis sales without doing the hard work needed to keep the public safe.
In Canada, which legalized recreational marijuana in 2018, one study found a 475% increase in emergency-room visits for cannabis-related crashes in Ontario between 2010 and 2021. Many more cases likely went undetected, owing to a dearth of reliable testing for driving while high.
In the US, the proportion of motor-vehicle fatalities involving cannabis use soared to 21.5% in 2018, up from 9% in 2000. One analysis found a 10% increase in vehicular deaths, on average, following legalization by states. In California, the increase was 14%; in Oregon, it was 22%.
This suggests that more than 1,000 Americans could be dying annually because of marijuana-related accidents — and that’s just in states where legalization has occurred. Given the ease of transporting the drug across state lines, the real number could be far higher.

The cause of these deaths isn’t just the drug itself. It’s ignorance. A recent study found that about half of marijuana users thought they were OK to drive 90 minutes after inhaling or ingesting the drug, yet their driving performance in a simulated vehicle was as bad as it had been after 30 minutes. The best available evidence suggests that people should wait a minimum of four hours before getting behind the wheel; some experts recommend eight to 12 hours.

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Cannabis and Driving in Older Adults

Question: What is the association between retail cannabis available to the consumer, driving, and associated blood tetrahydrocannabinol (THC) levels in people over 65 years of age?

Findings: In this cohort study, 31 regular users of cannabis aged 65 to 79 years chose on average high potency (18.74% THC) THC-dominant cannabis. Weaving was increased and speed was decreased at 30 minutes after smoking, which was not correlated with blood THC concentrations; subjective experience and self-reports of impaired driving persisted for 3 hours. 

Meaning: These findings suggest that older drivers, even if they regularly use cannabis, show evidence of impaired driving performance after smoking cannabis

Source Cannabis and Driving in Older Adults | Geriatrics | JAMA Network

A study by McLean Hospital’s Mary Kathryn Dahlgren, PhD, Staci Gruber, PhD, and their team from McLean’s Cognitive and Clinical Neuroimaging Core and the Marijuana Investigations for Neuroscientific Discovery (MIND) program, has found that recreational cannabis use affects driving ability even when users are not intoxicated by marijuana.

Published in the Drug and Alcohol Dependence journal, the study “Recreational Cannabis Use Impairs Driving Performance in the Absence of Acute Intoxication,” finds that in addition to chronic, heavy, recreational cannabis use being associated with poorer driving performance in non-intoxicated individuals compared to non-users, the researchers linked earlier onset of marijuana use (under age 16) to worse performance.

Study at a Glance

• McLean researchers have discovered that recreational marijuana use affects driving ability even when users are not intoxicated
• The study, conducted through driving simulation, concluded that chronic, heavy, recreational marijuana use was associated with worse driving performance in non-intoxicated drivers compared to non-using healthy control participants
• Cannabis users had more accidents, drove at higher speeds, and drove through more red lights than non-users
• Earlier onset of marijuana use (regular use prior to age 16) was associated with poorer driving performance
• Findings may be reflective of increased impulsivity in those who initiate substance use during adolescence; further research will explore this association

Recreational cannabis use has expanded across the United States in the last several decades and so has public concern about the substance’s impact on activities that present safety issues.

While several studies have examined the direct effect of cannabis intoxication on driving, no other studies until now have examined the effects on driving in heavy marijuana users who are not high.

Gruber, who is among the world’s foremost experts in the cognitive effects of marijuana, said the idea that differences can be detected in sober cannabis users may be surprising to the public.

“People who use cannabis don’t necessarily assume that they may drive differently, even when they’re not high,” she said. “We’re not suggesting that everyone who uses cannabis will demonstrate impaired driving, but it’s interesting that in a sample of non-intoxicated participants, there are still differences in those who use cannabis relative to those who don’t.”

Also see

• Cannabis use altering key functions like three-dimensional vision
• 'Medicinal’ Cannabis & Driving – Is it an Issue?

For Complete Research

Cannabis-Involved Traffic Injury Emergency Department Visits After Cannabis Legalization and Commercialization

JAMA Netw Open. 2023;6(9):e2331551. doi:10.1001/jamanetworkopen.2023.31551

Key Points

Question  Have cannabis-involved traffic injury emergency department visits changed after cannabis legalization and the subsequent commercialization of the cannabis retail market (ie, store and product expansion) in Ontario, Canada?

Findings  In this cross-sectional study capturing 426 cannabis-involved traffic injury emergency department visits, annual rates of cannabis involvement increased by 475.3% over 13 years. After accounting for time trends, legalization with restrictions was not associated with increased cannabis involvement during traffic injury emergency department visits; however, market commercialization, which overlapped with the COVID-19 pandemic, was.

Conclusions and Relevance  This cross-sectional study found large increases in cannabis involvement in ED visits for traffic injury over time, which may have accelerated following nonmedical cannabis commercialization. Although the frequency of visits was rare, they may reflect broader changes in cannabis-impaired driving. Greater prevention efforts, including targeted education and policy measures, in regions with legal cannabis are indicated.

(Source: Emergency Medicine | JAMA Network Open | JAMA Network

Subtle but pervasive changes can occur between uses.

Understanding THC’s interaction with the brain’s important natural cannabinoid chemistry and physiology will now make sense of the impact that overly frequent cannabis use has on the brain and mental functioning.

Because THC stimulates our brain’s natural cannabinoid receptors (CB1) far more strongly and longer than the endogenous cannabinoid neurotransmitters anandamide and 2-AG, cannabis use throws brain chemistry out of balance temporarily, usually to people’s enjoyment. This loss of chemical equilibrium lasts an average of 4 hours when cannabis is inhaled and 8 hours when ingested orally before the liver metabolizes the THC and it is eliminated in the feces (55%) and urine (20%).

Most occasional cannabis users feel little or no effect the following day, but an interesting experiment reveals a subtle impact 24 hours after smoking a single joint. Private licensed pilots with over 200 hours of flight experience had their baseline skills measured in a flight simulator, then were provided a joint containing 10 or 20 mgs of THC to smoke. This was considered the equivalent of a moderate social dose in the mid-1980s.

A variety of pilot actions during routine landings were impaired 24 hours after smoking the joint, including the number and size of adjustments to stabilize the plane, distance off center on landing, and vertical and lateral deviation on approach to landing. Pilots showed no awareness of these impairments. Performance returned to baseline 48 hours after being high.

When the task became more complex by introducing turbulent weather conditions calling on pilots to react in real time to avoid trouble, responses were slower and less well organized than their baseline performance. In other words, the pilots’ response to novel events was altered (see the post How Cannabis Makes Everything So Interesting for clarification on the role our internal cannabinoid system plays in the experience of novelty.)

When THC stimulates CB1 receptors in the amygdala, cannabinoid tone increases, lowering the bar for any stimulus being imbued with a sense of novelty. Novelty draws our attention to unexpected stimuli. This phenomenon is largely responsible for cannabis making everything more interesting. But this is not the end of the story.

Whenever neurons containing CB1 receptors are over-stimulated by THC’s stronger and longer activation, a homeostatic response follows in an effort to rebalance the brain. The phrase “over-stimulated” means only that THC’s stimulation of CB1 receptors exceeds normal physiologic levels, leading to greater than normal negative feedback on the neuron’s release of transmitters with each firing. THC quells neuronal activity not by reducing the rate of nerve cell firing, but rather the amount of transmitter released each time the neuron fires.

As a result, neurons immediately react to THC’s over-stimulation by reducing the number of CB1 receptors. This reduction of receptors is called downregulation. A variety of mechanisms, including pulling receptors inside the cell so they are no longer available to be stimulated, begins with a single exposure to cannabis. By downregulating CB1 receptors, neurons partially regain some balance. Fewer receptors reduce the amount of negative feedback produced by cannabinoid stimulation and a more physiologic balance is re-established.

After THC has been metabolized and eliminated, CB1 receptors begin upregulating back to their normal level of availability. Upregulation after a single or occasional dose of cannabis occurs rapidly. Most people feel unaffected the following day.

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