The Science Behind Hangovers

According to the National Institutes of Health, alcohol produces both stimulant and sedative effects on people. Increased heart rate and aggression are associated with its stimulative effect, while motor slowing and cognitive impairment are examples of its sedative effect. Alcohol depresses the brain and slows down its ability to control the body and the mind. Muscle coordination, reflexes, movement and speech also slow down. If you drink too much, your heart rate or breathing can reach dangerously low levels.

At the same time, alcohol interferes with the normal sleep process. If you drink close to bedtime, your body may go straight into deep sleep and miss out on the usual first stage of sleep called rapid eye movement (REM) sleep. As the alcohol wears off, your body can come out of a deep sleep and back into REM sleep, which is much easier to wake up from. That’s why people often wake up after just a few hours of sleep when they’ve been drinking. In the course of a night, humans usually have six or seven cycles of REM sleep. However, if you’ve been drinking, you’ll typically have only one or two cycles, which means you may wake up feeling exhausted.