How Does Cannabis Use Affect Driving and Cognitive Abilities?

By Harry B. Nuggs

How Does Cannabis Use Affect Driving and Cognitive Abilities?

With more states legalizing cannabis for medical and recreational purposes, understanding the effects of cannabis on driving abilities is crucial. Many wonder - is driving under the influence of cannabis as dangerous as alcohol? Does cannabis meaningfully impair driving skills? Let's explore what the research says.

Impairment Factors

The degree to which cannabis impairs driving depends on several factors, including the strain's THC levels, consumption method, dose, tolerance levels, and individual physiology. Like alcohol, cannabis causes varied effects from person to person.


Smoking or vaping cannabis results in more immediate impairment compared to delayed effects from edibles. Someone new to cannabis is more likely to experience extreme sedation than an experienced user. The THC potency level also significantly impacts the intensity and duration of impairment.

Cannabis vs. Alcohol

Numerous studies demonstrate that alcohol still poses a greater overall risk to driving performance than cannabis. While both substances impair driving abilities, alcohol tends to bring on a lack of control, overconfidence, poor coordination, and belligerence.  


Cannabis impairs motorists differently - causing slower reaction times, altered perception of time and speed, diminished hand-eye coordination, and reduced ability to multi-task or remain attentive for extended periods. However, most cannabis-impaired drivers tend to be aware of their diminished capacities and drive more cautiously.

Simulator and Road Tests

Cutting-edge driving simulators and road test examinations give researchers deeper insights into how cannabis impacts various driving skills and behaviors. Overwhelmingly, studies show cannabis causes moderate impairment in areas like:


  • Reaction time and overall driving performance

  • Lane weaving and maintenance of lateral position

  • Judging time, distance, and speed

  • Visual attention span 

  • Divided attention ability to multitask

  • Motor coordination skills


However, cannabis does not appear to significantly impair a driver's ability to stay in their lane or maintain a consistent driving speed. Impairment is dose-dependent, wearing off substantially within 3-4 hours for most people.

Cannabis-Alcohol Combination

The combination of cannabis and alcohol together creates exponentially higher impairment risks compared to either substance alone. This dangerous mix leads to severely diminished driving abilities like poor vehicle control, slowed reactions, distortion of time/space, and lack of coordination.  


Simply put, never drive under the influence of both cannabis and alcohol. When consumed together, their impairments become amplified and compounded in unpredictable ways.

Effects on Cognitive Abilities

The research on cannabis and cognitive abilities pits some contradictory findings against conventional stereotypes about "stoners" being forgetful and unmotivated. Here's a closer look at how THC impacts the mind.


Memory and Learning

Cannabis appears to mildly impair short-term memory and the ability to acquire and retain new information or skills in the acute period after consuming. However, these impacts are temporary while the cannabinoids remain active in the body and brain.


For long-term or former cannabis users, research has found little to no residual deficits in memory, attention span, cognitive flexibility, or verbal skills when sober. Any impairments disappear within 3-4 weeks of sustained abstinence.


Focus and Concentration

Contrary to popular belief, cannabis does not necessarily undermine focus and concentration abilities across the board. In fact, low doses may enhance focus and flow states for certain tasks by mildly suppressing the brain's peripheral awareness of distractions.


However, cannabis can make it more challenging to rapidly juggle multiple tasks or quickly shift focus between different types of cognitive efforts. Multi-tasking, sustained attention, and task-switching degrade under the influence.


Executive Function

Higher doses of THC tend to temporarily disrupt executive functions of the brain, including rational decision-making, impulse control, flexible thinking, and self-regulation of behavior. Under the influence, some individuals struggle to solve problems, see multiple perspectives, or override habitual responses.


Cannabis may compromise motivation for certain tasks by temporarily blocking the brain's natural reward system. However, enhanced states of curiosity, introspection, and creativity often accompany this impairment in traditional goal-oriented functions.

Long-Term Effects?

While ongoing cannabis use during adolescence may negatively impact cognitive development in some areas, the research is still debated and inconclusive. Current evidence does not indicate any significant long-term detrimental effects on cognition for most adult cannabis consumers after periods of sustained abstinence.


That said, regular and heavy long-term consumption in adulthood remains an area needing further research. Some studies have linked persistent cannabis use to slightly diminished performance in areas like verbal memory, processing speed, and executive function over time.

Use Responsibly 

Like other psychoactive substances, cannabis impairs driving abilities and certain cognitive functions in dose-dependent ways. For safety, never drive while under the influence. Avoid mixing cannabis with alcohol or other depressants. Be aware of timing dosage for activities requiring critical thinking, memory, focus, and coordination.  


Overall, cannabis affects each individual differently based on history of use, consumption methods, dosage levels, age, and biology. By using responsibly and knowing your limits/reactions, you can enjoy the potential benefits of cannabis while minimizing drawbacks and risks. Moderation is key.