Many people enjoy the stimulating effects that come from drinking coffee or other caffeinated beverages. The downside of such beverages, however, is that they can create a dependence on caffeine. As a consequence, when a person is deprived of his usual dose, he may suffer temporary but sometimes debilitating symptoms. A headache, together with fatigue, depression, difficulty concentrating and even flu-like symptoms, can result. Research has shown that headache and other caffeine withdrawal symptoms are quite real and have a scientific basis.
Caffeine as an Addictive Substance
Researchers at Johns Hopkins University identified headache as one of the most common caffeine withdrawal symptoms. Experimental studies showed that half of subjects experienced a headache because of caffeine withdrawal, while 13 percent experienced pronounced symptoms such as severe headache that rendered them functionally impaired. The symptoms typically became noticeable between 12 and 24 hours after stopping caffeine. Symptoms were worse in the first couple of days and lasted from two to nine days. Although the severity of headache and other symptoms brought on by abstaining from caffeine was greater in those who normally consumed larger doses of caffeine, even those who typically drank only one small cup of coffee also suffered symptoms.
Increased Cerebral Blood Flow
When a person who is accustomed to drinking a caffeinated beverage abstains, blood flow to his brain increases. A study published in the journal "Human Brain Mapping" used magnetic resonance imaging to measure the cerebral blood flow of caffeine users in both a caffeinated state and in an abstained state. Results showed that caffeine reduced subjects' cerebral blood flow by an average of 27 percent. In the abstained state, moderate- to high-caffeine users had greater cerebral blood flow than low-caffeine users. The increased blood flow in the brain may account for the headache many people experience during caffeine withdrawal. In fact, numerous pain relievers contain caffeine as an ingredient because of its effectiveness in constricting dilated blood vessels.
Adenosine
Caffeine withdrawal can also be the result of an increased sensitivity to adenosine, an important chemical neurotransmitter that circulates in the blood, according to studies at Johns Hopkins Medical School as reported in "Psychology Today." "All the effects of taking caffeine are opposite of the effects of adenosine," states Roland Griffiths, professor of psychiatry and neuroscience at Johns Hopkins. Adenosine acts to depress the nervous system and dilate blood vessels in the head, while caffeine acts as a stimulant and restricts the blood vessels. If caffeine is suddenly withdrawn from a habitual coffee drinker, the increased blood flow can lead to a bad headache.
Rebound Headaches
Many, though not all, analgesics contain caffeine. Caffeine helps the medicine work more quickly, and it actually increases the medication's effectiveness by 40 percent, according to the Cleveland Clinic. A rebound headache can occur from the overuse of any headache-relieving medication, whether it contains caffeine or not. But headache medications that do contain caffeine, particularly when taken in combination with a caffeinated beverage or food, make it more likely you'll develop another headache as soon as the effects of the medicine and caffeine wear off.
References
- ScienceDaily; Caffeine Withdrawal Headache Explained: Your Brain On -- And Off -- Caffeine; May 2009
- "Human Brain Mapping"; The Effect of Daily Caffeine Use on Cerebral Blood Flow: How Much Caffeine Can We Tolerate?; Merideth A. Addicott, et al.; October 2009
- "The New York Times"; Bodily Interaction Found to Explain Caffeine Withdrawl Headache; Jane E. Brody; April 1982
- "Psychology Today"; Crazy for Coffee; Carlin Flora; November 2004
- Cleveland Clinic: Caffeine and Headache
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