Coffee, tea, and energy drinks all contain caffeine. Caffeine is a stimulant. After a strong caffeinated drink, a person feels happier and more energetic. Caffeine affects brain chemicals that control relaxation. Too much caffeine will affect sleep. After drinking a lot of caffeine, some people have insomnia. Scientists found that caffeine affects other chemicals in the body. These chemicals control sleep.

Melatonin is a sleep hormone. Melatonin levels are high in the evening, and a person falls asleep. They are low in the morning, and a person wakes up. The rhythms of sleeping and waking up are called “circadian rhythms” and the “body clock.” Caffeine affects melatonin production. A cup of coffee in the morning can affect sleep at night. This is not good news for coffee drinkers, but scientists want to experiment with caffeine and melatonin.