Top 5 Effects of Caffeine on the Brain | Visualized Health

Reviewed by The Clinical Committee

July 13, 2019

  • Studies across several decades have all shown caffeine to have positive effects on the brain.

  • Caffeine lowers your reaction time, reduces sleepiness, and improves cognition among other documented effects.

  • When taken in moderation, caffeine should be at least somewhat beneficial for most people.


Caffeine has its greatest effects on your brain and your nervous system. It affects you think and react. Fortunately, most of the research thus far has pointed to generally positive effects of caffeine.

Top 5 Effects of Caffeine on the Brain


Reaction Time

A small dose of caffeine (64mg) has been shown to significantly improve reaction time. Reaction Time measures how quickly we respond to a certain stimulus. This is particularly relevant to driving and athletics. For example, a faster reaction time with caffeine would mean that we can hit the brakes faster to avoid an accident. In sports, faster reaction times help us stay one step ahead of our opponents.

Reference: Journal of Clinical Psychopharmacology

"We observed that caffeine (64 mg), when added to aspirin (800 mg), significantly improves vigilance performance and increases self-reported efficiency when compared with either placebo or aspirin alone. As previously reported, this caffeine dose alone significantly increased vigilance and decreased reaction time. No adverse effects of caffeine were detected on any of the parameters that were assessed."


Less Sleepiness

As much as we all love a good nights sleep, this isn’t always possible. In order to test the effects of caffeine and sleepiness, researchers studied Navy SEAL trainees, who are constantly sleep deprived and physically challenged during their training. They found that when Navy SEAL trainees are sleep deprived and put into stressful situation, taking caffeine helped them recover from the negative effects of sleep deprevation across multiple cognitive tests.

Reference: Psychopharmacology

"Sleep deprivation and environmental stress adversely affected performance and mood. Caffeine, in a dose-dependent manner, mitigated many adverse effects of exposure to multiple stressors. Caffeine (200 and 300 mg) significantly improved visual vigilance, choice reaction time, repeated acquisition, self-reported fatigue and sleepiness with the greatest effects on tests of vigilance, reaction time, and alertness."



Vigilance represents the ability to stay concentrated and alert over a long period of time. This is particularly important for those working in transportation, law-enforcement, and healthcare. Researchers have found a particularly for those were sleep deprived, caffeine can significantly improve vigilance. This means that caffeine can help surgeons stay on-point during long procedures, help soldiers stay more alert while standing watch, and help police officers do a better job keeping themselves and our cities safe.

Reference: Aviat Space Environ Med

"Lapses on the PVT were categorized as response times greater than 1, 3, or 5 s. Lapses in all categories significantly increased in the placebo group. Caffeine significantly reduced the number of lapses in a dose-related manner; and performance was maintained at baseline levels for the entire sleep loss period with multiple doses of 200 mg caffeine...These results indicate that a bi-hourly administration of 200 mg of caffeine maintains vigilance performance across a single night without sleep."


Jet Lag + Shift Work

Caffeine can help us handle the consequences of jet lag and shift work. Shift work, when we sometimes work the night shift and sometimes work the day shift, can have similar effects as jet lag. In both cases, our bodies’ own internal clock has to constantly undergo significant shifts leading to mostly negative effects on our mental state and mood. Research has shown that caffeine can potentially help us recover from and handle the negative effects of jet lag and shift work.

Reference: Aviat Space Environ Med

"Sleepiness leads to a deterioration in performance and attention, and is associated with an increased risk of injury. Jet lag and shift work disorder are circadian rhythm sleep disorders which result in sleepiness and can elevate injury risk...The pooled effect estimates on performance by cognitive domain suggest that, when compared to placebo, caffeine improved concept formation and reasoning (SMD -0.41; 95% CI -1.04 to 0.23), memory (SMD -1.08; 95% CI -2.07 to -0.09), orientation and attention (SMD -0.55; 95% CI -0.83 to -0.27) and perception (SMD -0.77; 95% CI -1.73 to 0.20); although there was no beneficial effect on verbal functioning and language skills (SMD 0.18; 95% CI -0.50 to 0.87)."



There is some evidence showing that taking in lots of caffeine may correlate with cognitive performance. The data suggests that drinking coffee literally correlates with being smarter. However, we will likely need more research before we can confirm this affect for sure. As with all such studies, it is very possible that this correlation does not represent causation.

Reference: Psychopharmacology (berl).

"Estimated overall caffeine consumption showed a dose-response relationship to improved cognitive performance (P<0.001 for each cognitive test, after controlling for confounders). Older people appeared to be more susceptible to the performance-improving effects of caffeine than were younger. The results suggest that tolerance to the performance-enhancing effects of caffeine, if it occurs at all, is incomplete."

More Information on Caffeine


If coffee helps you get up in the morning and perform at your best, then keep on drinking it. The scientific studies above only confirm what us coffee drinkers have known all along. Caffeine keeps us vigilant, alert, and awake.

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