Caffeine is the most widely used psychoactive drug in the world. It exists naturally in plants and can also be produced synthetically and added to foods and beverages. Although frequently ingested through food (e.g., chocolate) and sometimes in pain, cold, or diet medication, caffeine is most often consumed through beverages such as coffee, tea, and carbonated soda or sodalike beverages (including many energy drinks). The amount of caffeine in coffee varies based on the size of the serving, the type of coffee, and how the coffee is prepared. According to the U.S. National Institute of Health, a 250-ml cup of coffee can vary in the quantity of contained caffeine from 5 mg in decaffeinated coffee to 30 mg to 120 mg in instant coffee and to 40 mg to 180 mg in brewed coffee. In comparison, brewed tea can contain 20 mg to 90 mg, instant tea roughly 28 mg, common soft drinks 36 mg to 90 mg, and chocolate milk 3 mg to 6 mg of caffeine. In the United States, as well as in many other countries, caffeine does not have to be listed on product labels unless it has been added to the product separately. In other words, if a product contains another substance (e.g., yerba maté) that naturally includes caffeine, caffeine does not have to be listed as a separate ingredient.
Caffeine is not a nutrient that the body requires for optimal healthy functioning. Rather, it belongs to the class of drugs popularly called central nervous system stimulants due to their ability to heighten physical and psychological functioning. Several sources, including the American Psychiatric Association, note that the average daily consumption of caffeine among American adults is at least 200 mg to 300 mg a day (equivalent to about two to three cups of regular coffee) and that roughly 80% of Americans consume caffeine daily. Along with its reported beneficial effects, caffeine carries with it a host of possible adverse consequences. Such consequences, combined with caffeine’s prevalent use in North America, have triggered a growing concern over this legally sanctioned drug.
The U.S. Food and Drug Administration (FDA) recognizes caffeine under the category of “Generally Recognized as Safe” for moderate consumption, and the American Medical Association maintains a similar position. However, the concept of moderate consumption is unique to every individual and depends on factors such as an individual’s health and body makeup. For example, some individuals can drink several caffeinated beverages in short succession and experience little or no effects while others may experience caffeine’s stimulating properties after consuming only one.
Ubiquitous caffeine use raises the question of how much is too much. Whereas the United States does not hold official national guidelines for general caffeine consumption, such principles are available in Canada. For the general adult population, Health Canada recommends a maximum of 400 mg per day, the equivalent of three to four 8 ounce cups of brewed coffee. Health Canada’s recommendation for caffeine intake for women of childbearing age who are anticipating pregnancy in the future was lowered in 2003 based on new research. They reported that these women are at increased risk of adverse reproductive effects and should not exceed more than 300 mg per day. This recommendation is inline with those made by the U.S. National Institute of Health, which stated that caffeine consumption over 300 mg per day by pregnant women results in an increased risk of miscarriage and in slowed growth of a developing fetus. Children are at much greater risk for the negative behavioral consequences that can result from caffeine use. For those age 12 and under, based on average body weight, Health Canada recommends a maximum daily intake of 45 mg for children ages 4 to 6, 62.5 mg for children ages 7 to 9 and 85 mg for children ages 10 to 12.
Once caffeine enters the body, the effects can be felt by some individuals within 15 minutes. Upon consumption, caffeine produces diverse psychological and physiological effects largely through stimulation of the central nervous system. Doses of caffeine under the recommended limits can produce increased energy, alertness, and sociability while also serving to elevate mood. In addition, individuals who have consumed up to such a moderate dose report enhanced cognitive performance, the ability to sustain attention for longer periods, and a partial counteracting of performance detriments associated with sleep deprivation. In light of these desirable effects, many individuals are unaware of the potentially negative consequences of caffeine use. Even within recommended limits, caffeine has been found to result in insomnia and increased blood pressure. In higher doses, caffeine has been shown to produce anxiety, jitteriness, stomach pain, diarrhea, dehydration, dizziness, rapid heart beat, blurred vision, severe confusion (delirium), muscle tremors, nausea, vomiting, increased sensitivity to touch and pain, seizures, and decreased bone density.
Although alcohol and other psychoactive drug use have been closely monitored in national surveys, such is not the case for caffeine. Although caffeine consumption has become an everyday part of many people’s lives, caffeine is nonetheless a potential drug of abuse. For example, caffeine use can lead to withdrawal symptoms, the development of tolerance, and other dependence-type symptoms (e.g., preoccupation with thoughts related to its use, unsuccessful attempts to stop usage, using more than intended). Furthermore, caffeine is included in the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision (DSM-IV-TR), published by the American Psychiatric Association, by means of the following psychiatric disorders: caffeine-intoxication, caffeine-induced anxiety disorder, caffeine-induced sleep disorder, and caffeine-related disorder not otherwise specified (a catchall category of other caffeine-related conditions). In-line with the DSM-IV-TR, the International Classification of Diseases, Tenth Edition (ICD-10), published by the World Health Organization, lists “mental and behavioral disorders due to use of other stimulants, including caffeine” and “poisoning: psychostimulants with abuse potential,” a category that includes caffeine.
When an individual whose body has become accustomed to certain levels of caffeine stops ingesting caffeine, a range of unpleasant physical and psychological consequences may result. The most comprehensive review of the effects of caffeine withdrawal to date, completed by Laura Juliano of American University and Roland Griffiths of Johns Hopkins University, validated the following as the key symptoms of caffeine withdrawal upon abrupt discontinuation of its use (even at doses as low as 100 mg per day): headaches, decreased energy, tiredness, depressed mood, heartburn, sleep difficulty, irritability, general anxiety, decreased alertness, drowsiness, and difficulty concentrating. Withdrawal symptoms tend to peak during the first 12 to 24 hours after the last use of caffeine and typically end within a week. The potential for caffeine withdrawal to cause clinically significant distress or impairment in functioning is reflected by the inclusion of caffeine withdrawal as a diagnosis in the ICD-10 and as a condition in need of further study for possible future inclusion by the DSM-IV-TR.
Central Nervous System Stimulants; Diagnostic and Statistical Manual of Mental Disorders; Substance-Induced Disorders; Substance Use Disorders
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