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.
This drug is also found in the breast milk of coffee-drinking mothers. Regular users experience physical dependence to the drug and may suffer withdrawal symptoms, including tension headaches and irritability, when they are deprived of the drug. Many coffee drinkers also have a psychological dependence to caffeine, feeling they need a cup or two in the morning to get going.