Caffeine is a stimulatory chemical present in coffee, tea, some medications, sodas and chocolate and is added to many energy drinks. Normal consumption levels of a few coffees or sodas, about 250 mg a day, is considered safe and doesn't usually cause problems beyond jitteriness, restlessness and irritability. Increasing caffeine consumption increases the risk of serious side effects.
Caffeine is a stimulant used mostly to fight fatigue and increase energy. Excessive levels can have the opposite effect. The Maternal and Child Health Bureau of the Department of Health and Human Services in Maryland examined the association between caffeine and fatigue in adolescents. The study was reported in the April 2006 edition of the "Journal of Adolescent Health," concluding that students reporting a high caffeine intake were almost two times as likely to have trouble falling asleep and to be tired in the morning due to interrupted sleep patterns.
Caffeine has been associated with fertility and pregnancy problems. The March of Dimes recommends an upper limit of 200 mg or a 12-oz. cup of coffee, during pregnancy. In March 2008, the "American Journal of Obstetrics and Gynecology" published a study concluding that risk of miscarriage increases with caffeine consumption of 200 mg or more, independent of pregnancy-related issues such as vomiting, previous miscarriage, smoking or alcohol use. According to a study in the "British Medical Journal" February 2003, risk of stillbirth was almost double for women consuming eight cups of coffee or more per day than women who did not consume coffee.
Caffeine functions in the central nervous system and may exacerbate or create situations of mental illness. In March 2010, the "The American Journal of Psychiatry" presented a case study of excessive caffeine intake. The schizophrenic patient had been in remission and stable for many years and managed by medication. After consuming an energy drink and feeling both physically and mentally alert, the patient increased intake up to eight to 10 cans, or more than 1,000 mg of caffeine per day. Within a few weeks he was hospitalized for paranoia and delusion. The Department of Psychology at Brigham Young University reported the case of a healthy, 47-year old man who developed psychosis characterized by paranoia and delusions from consuming high levels of caffeine. Symptoms subsided over a few weeks as caffeine intake decreased.
Extremely high levels of caffeine can cause death. On October 28, 2010, the BBC News Nottingham reported on the death of a young man due to consuming 2 tsp. of powdered caffeine bought from an online source. He began vomiting and slurring words and died later at the hospital. Recommendations are for no more than 1/16 tsp. The coroner, Dr. Nigel Chapman estimated that the man had taken more than 70 times the amount of caffeine usually found in energy drinks.