Condition

Driving Performance

Driving performance is your ability to stay alert, react quickly and hold attention, and it slips with sleep loss, monotonous roads, long stretches without breaks and the body's natural low points. Caffeine has the strongest evidence, with research pointing to less fatigue and quicker reactions, while L-theanine, which may add calm focus, has moderate support. Other supplements have thinner evidence, and cannabis, tested in 147 people, showed no clear difference in driving caution.

Supplements studied: 1
Graded outcomes: 1
Trials: 4
People studied: 173

Evidence by supplement

Strong
Moderate
Limited
Very limited

1 supplement

Cannabis

Cannabis: outcomes studied for Driving Performance
Grade	Outcome	Effect	Size	Studies	People
	Driving Caution No effect		NoneNo effect		147 people
	Driving Speed	Improves (the measure goes up)		4 studies	147 people
Studies that measured driving speed Cannabidiol (CBD) content in vaporized cannabis does not prevent tetrahydrocannabinol (THC)-induced impairment of driving and cognitionPsychopharmacology · PMID 31044290 Acute and residual effects of smoked cannabis: Impact on driving speed and lateral control, heart rate, and self-reported drug effectsDrug Alcohol Depend · PMID 31678833 Cannabis use and driving-related performance in young recreational users: a within-subject randomized clinical trialCMAJ Open · PMID 30323055 and 1 more on the Cannabis page
	Driving Control	Improves (the measure goes up)		3 studies	173 people
Studies that measured driving control Effect of cannabis use on cognitive functions and driving abilityJ Clin Psychiatry · PMID 10401919 Cannabis smoking impairs driving performance on the simulator and real driving: a randomized, double-blind, placebo-controlled, crossover trialFundam Clin Pharmacol · PMID 29752828 Effect of Cannabidiol and Δ9-Tetrahydrocannabinol on Driving Performance: A Randomized Clinical TrialJAMA · PMID 33258890

Key findings

Driving CautionCannabis

The Driving Performance & Alertness protocol

2 primary supplements · 6 supporting supplements

Caffeine100–200 mg as needed (equivalent to 1–2 cups of coffee)
L-Theanine100–200 mg (often combined with caffeine)

See the full protocol

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Studies cited

7 studies from PubMed

Effect of Cannabidiol and Δ9-Tetrahydrocannabinol on Driving Performance: A Randomized Clinical TrialJAMA · PMID 33258890
Sex differences in the effects of marijuana on simulated driving performanceJ Psychoactive Drugs · PMID 20464803
Cannabis use and driving-related performance in young recreational users: a within-subject randomized clinical trialCMAJ Open · PMID 30323055
Cannabis smoking impairs driving performance on the simulator and real driving: a randomized, double-blind, placebo-controlled, crossover trialFundam Clin Pharmacol · PMID 29752828
Effect of cannabis use on cognitive functions and driving abilityJ Clin Psychiatry · PMID 10401919
Acute and residual effects of smoked cannabis: Impact on driving speed and lateral control, heart rate, and self-reported drug effectsDrug Alcohol Depend · PMID 31678833
Cannabidiol (CBD) content in vaporized cannabis does not prevent tetrahydrocannabinol (THC)-induced impairment of driving and cognitionPsychopharmacology · PMID 31044290