Caffeine Abstinence Reduces Alertness in British Study

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Caffeinated beverages are often used as a “pick-me-up” or boost in alertness, but coffee drinkers may not get the same stimulating benefits as those who do not regularly consume, according to new research published online in the International Journal of Neuropsychopharmacology.

In the study, researchers from the University of Bristol surveyed 379 participants about their normal caffeine consumption and classified them according to their regular consumption. Light caffeine consumers were those who drank less than 40 milligrams per day, or less than the amount in one cup of coffee. Medium to heavy drinkers drank at least one, and up to 6 cups per day. The volunteers were also asked to rate their personal levels of anxiety, alertness, and headache before and after being given a dosage of caffeine or a placebo.

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Both light and heavy caffeine drinkers reported feeling more alert after being given caffeine, however light drinkers given caffeine did not report higher levels of alertness over regular coffee drinkers. Heavier caffeine drinkers given a placebo during the study were more likely to report a drop in their feelings of alertness and complained of having a headache, something the authors called a “caffeine hangover.”

The researchers also examined caffeine-induced anxiety, a common side effect that is more pronounced in people with a specific gene variant, called ADORA2A. Those who regularly consumed caffeine, even those with the genetic mutation, seemed to develop a tolerance to its anxiety-producing effects.

In humans, caffeine acts as a central nervous system stimulant, temporarily inducing alertness. The precise amount of caffeine necessary to produce effects varies from person to person. Caffeine is also chemically similar to adenosine, a neurotransmitter involved in regulating alertness and anxiety responses. Those who regularly consume caffeinated beverages adapt to its continuous presence and develop a tolerance to its effects, but also experience greater “withdrawal symptoms” when they abstain.

Study author Peter Rogers, a professor in the department of experimental psychology said that his study shows that consumers do not gain an advantage by consuming caffeine. "Although caffeine consumers feel alerted by caffeine, evidence suggests that this is merely the reversal of the fatiguing effects of acute caffeine withdrawal. On the other hand, while caffeine can increase anxiety, tolerance means that for most caffeine consumers this effect is negligible.”

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