Americans consume an average of five cups of coffee or an equal amount of caffeine in other drinks and food each day. Caffeine stimulates the central nervous system. Its effects range from mild alertness to heightened anxiety and body tension. It shortens reaction time among some users. But its impact on creativity and other intellectual activities is hard to define.
Caffeine can be habit-forming.
How caffeine affects you depends on what and how much you drink. Strongly brewed coffee or tea has more caffeine than a weakly brewed drink. As with other drugs, how much and how often caffeine is used can affect reactions. In addition, coffee nerves can cause behaviors that may annoy others and add tension to interpersonal interactions. Morning or afternoon slumps which affect everyone in some form are often used as rationale for drinking caffeinated beverages.