Psychological dependence, regardless of dosage, occurs among regular users. Caffeine Caffeine is a white, crystalline, bitter substance found in more than sixty plant species. The average dosage of caffeine is found in two cups of coffee. Effects are felt within 15 - 30 minutes of ingestion, and range from mild alertness to anxiety and muscle tension. Users may experience an increase in metabolism, body temperature, urine output, blood pressure, blood sugar and stomach acid.
Caffeine shortens reaction time to visual and auditory stimuli.
Moderate doses keep the user awake, increase attention and delay boredom. High doses of caffeine cause nausea, diarrhea, insomnia, trembling and sensory disturbances. It has been used to treat hyperkinetic children and premature babies with breathing problems. Women with this disease might be at higher risk for developing cancer. Caffeine crosses the placental barrier, but there are no proven links to birth defects.