How long does cannabis impairment last?
Smoking, Vaping and Edibles Compared on Metrics of Cognitive, Psychomotor and Driving Impairment
The following is an informal meta-review of existing scientific literature regarding cannabis impairment. It is provided for informational purposes only.
Key Findings and Takeaways
• Cognitive Impairment: Acute smoked THC effects (memory, attention, etc.) peak within 30 minutes of use and typically fully recover within ~3–5 hours (3). Higher doses or oral ingestion can extend measurable cognitive impairment up to ~8–10 hours(3). Adolescents experience stronger cognitive deficits than adults at similar doses, suggesting they may need longer recovery time(6). Frequent / high tolerance users show smaller acute cognitive impairments and recover faster (at times even showing no obvious deficits on some tasks)(5).
• Motor/Psychomotor Impairment: Cannabis slows reaction time and impairs coordination for a few hours after use. Simple motor tasks often return to baseline by ~3 hours post-smoking for moderate doses (10). Large doses can cause motor impairment lasting 4–5 hours (9). Occasional users reliably show these deficits, whereas daily users are often not significantly impaired in motor tests at typical doses (5). No residual motor impairment is expected after the drug wears off (e.g., the next day when sober). Younger users might be more impacted acutely, though data are limited.
• Driving Performance: Cannabis impairs driving ability most in the first 1–2 hours, with effects like lane weaving, slower reactions, and reduced attention. For occasional adult users, a moderate inhaled dose (~10–15 mg THC) can cause unsafe driving for about 3–5 hours (2), while higher inhaled doses (~20 mg or more) can extend impairment to ~5–7 hours (3). Orally ingested THC (edibles) produces longer-lasting impairment, up to 8+ hours (3). Frequent users have much shorter impairment windows – many can abstain for only 2–4 hours and show negligible driving impairment (having developed tolerance) (4). However, taking an unusually large dose can still impair even tolerant users for several hours. Adolescents and young adults should be extremely cautious – given their heightened sensitivity, they should ideally refrain from driving for a longer period (perhaps >6–8 hours) after use. Mixing cannabis with alcohol is particularly dangerous, leading to far greater impairment than either alone and longer recovery time, so it should be strictly avoided.
Overall, modern studies underscore that the duration of cannabis impairment is highly variable. In an average adult occasional user, measurable impairment from a typical cannabis dose lasts around 4 hours, but this can range from under 2 hours (for a low dose) to 8–10 hours (for high edible doses)(3). Frequent users experience shorter and less pronounced impairment, whereas less experienced users and adolescents face stronger, potentially longer-lasting impairment. As cannabis potency and use continue to rise, these findings highlight the importance of waiting long enough after using cannabis to ensure full recovery of cognitive and motor functions before engaging in critical activities. In practical terms, individuals should wait at least 3–6 hours after moderate cannabis use before driving – and consider a longer delay (8+ hours) if they are inexperienced, consumed a high dose, used an edible, or still feel “high.”
Ultimately, safety comes first: understanding these impairment durations can help cannabis users make informed decisions and avoid accidents or errors while under the influence.
Discussion
For cannabis consumers, safety sensitive businesses and law enforcement officers, understanding the duration of impairment from cannabis, including differences in the various methods of ingestion, is crucial. After all, without this, using responsibly and enforcing safety for driving, operating machinery or engaging in tasks that require alertness and coordination is impossible. However, pinpointing exactly how long acute impairment persists after consumption can be complex, as it depends on several factors including the method of intake and an individual's unique physiology, potency of the product, and tolerance.
This blog post explores the various methods of marijuana ingestion and how the window of acute impairment varies for each.
Acute Cannabis intoxication causes short-term impairment in various domains – from memory and attention (cognitive), to coordination and reaction time (motor), and notably in driving performance. Recent research (from the last 5–10 years) has clarified how long this impairment last, and how factors like user frequency and age modify the duration. Modern cannabis products often have higher THC potency relative to cannabis from 10+ years ago, so contemporary studies reflect doses that can produce stronger and longer lasting effects than older research. Below, we summarize findings on cognitive, motor, and driving-related impairment windows, highlighting how long impairments persist and when recovery occurs, with distinctions by user type and age group.
When cannabis is smoked or vaped, the onset of effects is extremely rapid and are typically felt within minutes. Through combustion and inhalation of the product, THC is able to rapidly enter the bloodstream through the lungs and requires very little time to begin producing impairing effects. However, the duration of these effects is also much shorter than for edible marijuana.
Consuming cannabis edibles produces significantly different impairment duration, onset, and impairment compared to inhalation. Since the metabolic pathway for edible cannabis is entirely different, the onset of effects is significantly delayed when compared to inhaled THC. Typically, the high will begin to be experienced between 30 minutes to 2 hours after consumption. That said, some companies are marketing edibles that are designed to take effect much faster, often within 5-15 minutes. Fast acting edibles are most commonly found in the form of beverages or gummies.
The unpredictable rapidity of onset and the frequent challenges in dosing edibles accurately account for a large portion of the issues arising from their use. It’s therefore important that cannabis consumers discuss the effects and dose with their dispensary.
Cognitive Impairment and Recovery Time
Cannabis’s acute cognitive effects include impairment to memory (especially short-term/working memory), attention, concentration, and executive functions (like decision-making and inhibitions) (1). These effects set in quickly after use and generally peak within the first hour or two. For instance, one review noted that most acute neurocognitive impairments from THC occur within 90 minutes to 2 hours of use, and then subside during the next few hours (1).
Inhaled Cannabis
In occasional adult users, a moderate inhaled THC dose (~10 mg) tends to cause noticeable impairment at 30–60 minutes post-use, acute perceptible impairment lasts 90 minutes to 2 hours with performance metrics returning to baseline by about 4–5 hours after use (1). Higher doses prolong this window: e.g. inhaling ~20 mg THC can extend cognitive impairment up to ~6–7 hours (3).
Edible Cannabis
If cannabis is taken orally (edibles), the onset is slower and impairment lasts longer. Onset of acute impairment from edible cannabis commonly sets in between 30 and 90 minutes post consumption. High oral doses (e.g. 20–40 mg THC in edibles) may cause measurable cognitive deficits for 8–10 hours after ingestion (3). In fact, a recent meta-analysis of 80 studies confirmed a “window of impairment” between 3 and 10 hours depending on dose and route, with simpler cognitive tasks (like immediate recall or simple reaction time) typically recovering within ~4 hours at lower doses, while higher doses and more complex tasks (divided attention, etc.) may remain impaired for ~6–8 hours (3).
Tolerance
Frequent long-term cannabis users exhibit tolerance to many cognitive and acutely impairing effects of THC. This means they experience a smaller magnitude of impairment and faster recovery from that impairment, relative to occasional users at a given dose (1, 4). For example, a 2023 study comparing occasional vs. daily users found that after using their own high-THC cannabis (15–30% THC), occasional users showed significantly slowed reaction times and poorer working memory. Daily users on the other hand showed no significant change on these tasks post-use (5). This indicates that daily users have developed tolerance that blunts acute cognitive and psychomotor impairment.
Importantly, tolerance is often partial – heavy users might still show some deficits in certain domains (especially if using an unusually large dose), but they may recover more quickly. One review noted that even among experienced users, acute impairments can vary by domain, with some tasks (e.g. attention, decision-making) showing little change despite a high-potency cannabis dose, while others like psychomotor speed still show some slowing (1). In practical terms, a frequent user might be less impaired an hour or two after a typical dose than an infrequent user would be, but if the frequent user consumes a much higher dose to “get high,” they can still exhibit significant impairment and a prolonged recovery time (4).
How Age Effects Impairment from Cannabis
Age appears to be an important factor in understating marijuana impairment. Adolescents / young users are more susceptible to cannabis-induced cognitive deficits than older adults. A 2022 controlled study compared adolescents (18–20 years old) and adults (~30–40 years) after consuming THC capsules (7.5 and 15 mg). Both groups reported similar intoxication levels, but adolescents showed greater cognitive and behavioral impairment – including more slowed reaction times, worse response accuracy, and altered time perception (6). Adolescents had larger EEG changes (reduced P300 amplitudes) from THC, whereas adults showed little EEG change (6). In other words, at equivalent doses, the young group experienced stronger cognitive impairment than the adults (6).
This suggests that adolescents not only get more impaired, but they may require more time to fully recover normal cognitive function after use. It’s worth noting that direct studies on duration by age are limited due to ethical considerations, but the heightened sensitivity implies that standard “wait times” based on adult data might be insufficient for younger individuals (6).
Adolescents also appear to have longer term impacts to memory than adult cannabis users. Whereas adults do not demonstrate next-day effects (7), adolescents can experience residual cognitive effects into the next day (8). For example, new research on heavy young users found that memory and learning abilities can be impaired for 12–24 hours after use, even when the acute high has worn off (8).
The good news for adolescents who have experimented with cannabis is that these effects fade with abstinence – within 1–3 days post-use, such memory impairment was reduced by about half, and between 3–7 days, cognitive test scores returned near normal (8).
It’s worth reiterating that in adults, acute cognitive impairments from a single cannabis session are largely gone within hours and that no lingering impairment has been found the next day, but in adolescents and very heavy users, subtle cognitive deficits may linger into the next morning or longer.
Motor and Psychomotor Impairment
Motor function and coordination are acutely affected by THC use, manifesting as slower reaction times, impaired hand-eye coordination, and reduced motor control. These psychomotor impairments follow a time course similar to the previously mentioned cognitive effects. They are usually strongest soon after consumption and then resolve over several hours.
Experimental studies show that peak motor impairment (e.g. slow reaction speed or decreased motor inhibition) tends to occur within minutes to an hour after smoking/vaping, and then gradually improves over the next several hours. For instance, one study found that after smoking a 500 μg/kg dose of THC (approximately 35 mg for a 70 kg / 154 lb person), users’ ability in a stop-signal task was significantly impaired from 30 minutes up to 3.5 hours post-smoking, but by 5.5 hours after smoking the deficit had disappeared (9). A lower-dose study (cannabis cigarette with only 3.55% THC) similarly reported slowed reaction time at 30 minutes after smoking, but no impairment at 90 or 150 minutes later (9).
These results illustrate how dose/potency influences duration: with a low-potency cannabis, motor skills might recover within 1–2.5 hours, whereas a high dose can cause impairments lasting 3–5+ hours. In general, moderate doses produce motor slowing for several hours. A comprehensive review noted that across many studies, most psychomotor effects vanish by about 3–4 hours after use, aligning with the typical duration of the high (10). In fact, the number of significant performance deficits “sharply declined to about zero over 3–4 hours after THC use” in controlled lab tests (10).
However, usage frequency modulates these motor effects. Occasional users with no tolerance reliably show slowed reactions and impaired coordination when intoxicated (5). By contrast, frequent heavy users often show attenuated motor impairment – they may perform near normal on simple motor tasks even at THC levels that would impair an infrequent user.
In one recent trial, occasional smokers had clear slowing of reaction time after cannabis, but daily smokers showed no significant reaction time change at the same time-point (5). Similarly, daily users in that study did not exhibit the short-term memory deficits seen in occasionals (5), supporting the idea of functional tolerance. Another experiment observed that both occasional and heavy users had impaired performance on a challenging motor inhibition task (stop-signal), but on a simpler divided-attention task only the occasional users were impaired while heavy users maintained performance (10).
Tolerance develops to some, but not all, motor effects of cannabis (10). Heavy users may also unconsciously employ compensatory strategies to mask impairment (e.g. concentrating harder on tasks), but physiological measures (like EEG/brain activity) confirm that even when their performance looks unaffected, their brain may be working harder to compensate (10).
In summary, occasional users’ motor skills can be measurably slowed for several hours after getting high, whereas long-term daily users show much less motor impairment from an equivalent dose (and thus may recover baseline motor function sooner).
Age differences in motor impairment from cannabis are less studied due to the ethical concerns of exposing adolescents to THC, but likely parallel the cognitive trends. Since adolescents experience stronger acute intoxication effects on cognitive tasks, they likely also have greater motor impairment (e.g. slower reflexes, more clumsiness) for a given THC dose. Researchers have speculated that younger individuals may exhibit greater psychomotor impairment “on roads and highways” than adults for the same amount of cannabis (6).
Until more data are available, a prudent interpretation is that an adolescent user might need a longer period for full motor recovery post-cannabis, as their impairment at peak is greater. Regardless of age, no acute motor impairments have been found to remain after the drug’s effects wear off – i.e. there is no evidence of next-day motor skill impairment in sober individuals once THC’s acute action has ended (aside from extreme cases of very heavy use).
Cannabis does not create the prolonged physical motor incoordination that something like alcohol can cause into the “hangover” period; once THC’s effects resolve, motor function returns to normal. In heavy adolescent users, any enduring motor deficits are more likely related to long-term use patterns rather than a single use.
Driving-Related Impairment and Recovery
Driving is a highly complex skill that requires the integration of cognitive and motor abilities. Cannabis intoxication has been shown to impair several driving-related functions, including reaction time, lane-keeping (lateral control), distance judgment, and divided attention tasks, though typically to a modest degree compared to alcohol (1).
Over the past 5–10 years, rigorous studies (including on-road driving tests, simulators, and meta-analyses) have focused on how long after cannabis use driving performance remains impaired. In general, the consensus is that driving ability is most impaired in the first 1–2 hours after cannabis use, and then gradually improves, with most effects resolving by 4–6 hours for moderate doses (1). However, the exact duration of unsafe driving can vary widely depending on THC dose, route of intake, user tolerance, and even with the complexity of the driving scenario (ex. adverse weather or heavy traffic).
This chart shows the standard deviation of lateral position for cannabis users as compared to alcohol concentrations. 0.05 is considered to be impaired in the state of Utah and several other countries, while most of the United States considers 0.08 BAC to be impaired. Additional discussion below. Chart source: (11)
In a landmark on-road study (2), occasional users vaporized 13.75 mg THC (a moderate dose) or placebo and drove on a highway course. This data was used to create the chart above; the blue and red bars show the increase in lane weaving (SDLP – standard deviation of lateral position) at 40–100 minutes post-vaporization under THC conditions, compared to placebo. The dotted and solid lines indicate the equivalent impairment from blood alcohol concentrations of 0.02% and 0.05%, respectively (11).
At ~1 hour, THC caused a clear increase in weaving (similar to a ~0.05 BAC level) (2). By 240–300 minutes (4–5 hours) post-use, however, the blue bar (THC alone) had fallen near zero (no significant difference from placebo), indicating no detectable impairment in lane control (2). The red bar (THC/CBD combination) also dropped substantially by 4–5 hours. In other words, this study found significant driving impairment at ~1 hour, but not after 4 hours, from a 13.75 mg THC dose. The orange bar (CBD-only) condition showed minimal change at either time, reinforcing that CBD does not impair driving (2).
These results suggest that moderate inhaled doses of THC are unlikely to impair driving beyond about 4–5 hours in occasional users (2). Consistently, a recent review concluded impairment typically peaks during the first hour or two and dissipates by ~5 hours after inhalation of ~20 mg THC in most individuals (4). In fact, the meta-regression models in one analysis predicted that an occasional user’s driving impairment would last roughly 5 hours after smoking 10 mg THC, and around 8 hours after vaporizing 20 mg THC (1), illustrating the dose-dependent duration.
It’s important to note that task complexity matters. Simple driving-related tasks (like maintaining a steady speed on a low-traffic road) might recover sooner, whereas complex tasks (urban driving with many distractions, or emergency obstacle avoidance) may remain impaired longer. The meta-analysis by McCartney et al. 2021 found that most driving-related cognitive skills recovered within ~5 hours for inhaled THC, but more complex task performance (and real driving) showed almost full recovery by ~7 hours post-use (3).
When high doses are consumed, particularly orally (edible cannabis), impairment can extend to 8–10 hours, so driving any sooner could be unsafe (3). For example, a high-potency marijuana edible taken late in the evening might still meaningfully impair driving ability the next morning if less than ~8 hours have passed. As with the cognitive and psychomotor impairments discussed above, usage frequency (tolerance) plays a huge role in driving impairment. Occasional users have no tolerance and thus experience significant degradation in driving skills under the influence, whereas frequent users are less impaired at equivalent doses.
An on-road driving experiment comparing occasional vs. chronic cannabis users showed that after consuming THC, only the occasional users had substantial impairment, while the daily users (those with tolerance) showed no clinically relevant driving impairment at the same doses (10 mg or 20 mg THC) (4). This doesn’t mean experienced users are universally safe – rather, it reflects that tolerant individuals can handle moderate doses with minimal performance loss (4). If a heavy user pushes the dose much higher to overcome their tolerance, they can still become impaired and for just as long as an inexperienced person would (4). A 2022 clinical trial with regular (daily) cannabis users found that after smoking their typical amount, their driving simulator performance showed no significant deficits in lane position or braking compared to baseline – the main effect was a tendency to drive slightly slower than usual (1). This suggests regular users may consciously compensate (driving cautiously) and that their baseline driving might not be as affected except possibly by subtle factors.
Another study observed that frequent users displayed tolerance in cognitive and motor tasks relevant to driving, with little to no slowing of reaction time or memory impairment, whereas occasional users were clearly affected (5). Notably, chronic users with persistent THC in their bloodstream tend to have shorter impairment durations – one study found those with higher baseline THC levels (indicative of heavy use) recovered faster, showing a shorter window of self-reported impairment, than those with no THC in their system prior to smoking (12). This aligns with the idea that tolerance shortens the impairment period.
Age-related differences in driving impairment per se have not been directly studied as much (since experimental cannabis driving studies typically use adults). Nevertheless, given adolescents’ greater acute cognitive/motor impairment (6), a young or inexperienced driver might be at even higher risk and might require more than the standard 5–6 hours to be safe. Impairment aside, adolescents also lack driving experience, compounding risk. Epidemiological data show younger drivers already have higher crash risks, so adding cannabis could be particularly detrimental. Experts generally advise that no one (regardless of age) should drive for several hours after using cannabis, with one high quality clinical trial showing that users should wait at least 4 hours 30 minutes after getting high before driving (13).
Some studies have recommended a waiting period of 6-8 hours after use. This buffer is especially prudent for adolescents or very occasional / low tolerance users. By contrast, frequent adult users (e.g. medical patients using daily) might not need to wait as long after a routine dose – but they still should be cautious, any not drive if they feel any effects. This is underscored by a study that measured self-assessed willingness to drive by cannabis users. In the study, 191 cannabis users were measured on driving performance and asked when they would consider themselves safe to drive. The average user was willing to drive at 1 hour 30 minutes, while their driving performance was impaired for 4 hours 30 minutes (13). Ultimately therefore, self-assessment is unreliable, so erring on the side of a longer wait is important, particularly for safety-sensitive activities like driving.
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