Caffeine: Mental effects
Last modified: Thursday, 25. December 2008 - 8:57 am
Within minutes of consumption, a caffeinated beverage will cause the drinker to feel more alert. Simple intellectual tasks are performed more readily, as are physical jobs that require endurance. However, while reaction time is shortened by caffeine, fine motor control suffers, perhaps due to the slight tremor that becomes more pronounced with higher doses of caffeine. The larger doses of caffeine, especially for people who do not use it regularly, cause headache and nervousness.
Caffeine decreases the duration of slow waves in the electroencephalogram (EEG) for about five hours after it is ingested. Taken near bedtime, caffeine will delay the time it takes for the consumer to fall asleep, and will reduce the depth and quality of sleep. Sleepers will also move more and waken more easily. These effects are evident with the amount of caffeine present in a cup or two of coffee, approximately 75-150 mg.