When & Why Steer Clear? | Most Steer Clear

Marijuana impairment can last at least 6-8 hours after use, putting you at risk of driving under the influence (DUI) of cannabis

Initiative 502 set DUI of cannabis at 5 nanograms of THC per milliliter of blood for those over 21 years of age, and any positive amount for those under 21. This “per se” limit (meaning if you are above either of these cutoffs, you meet criteria for a DUI regardless of other factors) was selected because it is associated with decreases in reaction time and challenges in shifting focus. One study shows it takes 3 hours to drop below 4.9 nanograms of THC per milliliter of blood, meaning driving within three hours of use would likely result in being above our state’s cutoffs. More recent studies suggest impairment can last 6-8 hours [14], especially with more potent weed, edibles, or medical marijuana.

Marijuana significantly impairs judgment, motor coordination, and reaction time. [3]
Drivers with THC in their blood are twice as likely to be responsible for a fatal crash as drivers who had not used drugs or alcohol. [3]
Marijuana is the illicit drug most frequently found in the blood of drivers who have been involved in vehicle crashes, including fatal ones. [3]
There is substantial evidence that cannabis use increases the risk of motor vehicle crashes. Analyses of multiple studies found that the risk of being involved in a crash significantly increased after marijuana use. However, a large case-control study conducted by the National Highway Traffic Safety Administration found no significant increase in crashes attributable to cannabis after controlling for drivers’ age, gender, race, and presence of alcohol. [1,3]
The majority (81%) of delta-9 THC positive drivers in fatal crashes were male. [18]
Nearly one-third of drivers in fatal crashes positive for delta-9 THC were between the ages of 16 and 25. [18]
From 2018-2022 30.7% of young adults drivers ages 16-25 were involved in fatal crashes and tested positive for Marijuana. [18]
Delta-9-THC drivers also exhibited other high risk behaviors, such as speeding (42%), not wearing a seat belt (28%), and being distracted (16%). [18]

Alcohol in combination with marijuana significantly increases driving impairment. [11]
About 44% of delta-9 THC-positive drivers in fatal crashes also had a BAC of 0.08 or greater. [18]
In total, three out of four delta-9 THC positive drivers in fatal crashes were also positive alcohol and/or other drugs [18]

“[Until early-mid 20s] the brain is thought to be particularly sensitive to damage from drug exposure. And the frontal cortex — the region critical to planning, judgment, decision-making and personality — is one of the last areas to fully develop.”- Staci Gruber, PhD, director of the Marijuana Investigations for Neuroscientific Discovery (MIND) Program at Harvard Medical School.

Marijuana can have negative effects on attention, memory, and learning that can last for days or weeks after the acute effects of the drug wear off. [9]

“Regular, heavy [adolescent] users — those who reported smoking five of the last seven days, and more than 2,500 times in their lives — had damage to their brains’ white matter, which helps enable communication among neurons.” [5,6]

Marijuana use, especially among those who use heavily, has significant associations with increases in schizophrenia or other psychoses and moderate associations with other mental health issues including depression, suicide, and bipolar and social anxiety disorders. [9]
Using marijuana as a coping technique for problems is significantly associated with increased distress. [16]
Among 27 studies examining marijuana use in adolescents with anxiety, the majority (67%) found a positive association between marijuana use and anxiety. [17]

Marijuana has “negative effects on attention, memory, and learning that can last for days or weeks after the acute effects of the drug wear off.”
Most “adolescents who used marijuana regularly were significantly less likely than their non-using peers to finish high school or obtain a degree.” [9]
Evidence suggests that students who smoke marijuana have poorer educational outcomes than their nonsmoking peers [20]

THC can be passed to babies through breast milk and accumulate to high concentrations. [12]
Marijuana use during pregnancy has a high association with low birth weight babies. [12]
Using cannabis during pregnancy can harm fetal brain development and negatively affect kids later in life, including problems with their attention, memory, problem-solving skills, and behavior. [15]
Research on the health impacts of cannabis on pregnant women is still limited. However, when it comes to pregnancy and children, it makes sense to use a precautionary approach.