Headache
Caffeine is a psychoactive substance that stimulates the central nervous system. However, too much caffeine can cause headaches and migraine attacks. Caffeine works by blocking adenosine receptors in the brain. Adenosine promotes sleepiness. However, when caffeine blocks adenosine receptors, it results in increased alertness.
Caffeine also causes the release of other neurotransmitters, such as dopamine and norepinephrine. These neurotransmitters are associated with pleasure and can create a feeling of euphoria. In large amounts, however, they can lead to anxiety and restlessness.
The pharmacologic half-life of caffeine is about 5 hours, which means that if an individual consumes 200 mg of caffeine at 8 a.m., they still have 100 mg in the system at 1 p.m. The half-life of caffeine varies from person to person, but it depends on factors such as age, liver function, and the use of certain medications.
Caffeine withdrawal can cause headaches. Individuals who regularly consume caffeinated beverages or use medications that contain caffeine and then suddenly stop may experience headaches or migraines within 12 to 24 hours after their last dose. Caffeine withdrawal headaches usually peak after one or two days and gradually resolve over a week.
