Hangover

A hangover (veisalgia) describes the sum of unpleasant physiological effects following heavy consumption of alcoholic beverages. An alcohol hangover is associated with a variety of symptoms that may include dehydration, fatigue, headache, nausea, vomiting, diarrhea, flatulence, weakness, elevated body temperature, hypersalivation, difficulty concentrating, sweating, anxiety, dysphoria, irritability, sensitivity to light and noise, erratic motor functions (including tremor), trouble sleeping, severe hunger, halithosis, and lack of depth perception. Many people will also be repulsed by the thought, taste or smell of alcohol during a hangover. The symptoms vary from person to person, and occasion to occasion, usually beginning several hours after drinking. It is not clear whether hangovers directly affect cognitive abilities.

A hangover may also induce psychological symptoms including heightened feelings of depression and anxiety.

The term hangover was originally a 19th Century expression describing unfinished business—something left over from a meeting—or "survival". In 1904, the meaning "morning after-effect of drinking too much" first surfaced.

Hypoglycemia, dehydration, acetaldehyde intoxication, and vitamin B12 deficiency are all theorized causes of hangover symptoms. Hangovers symptoms may persist for several days after alcohol was last consumed. Approximately 25-30% of drinkers may be resistant to hangover symptoms. Some aspects of a hangover are viewed as symptoms of acute ethanol withdrawal, similar to the longer-duration effects of withdrawal from alcoholism, as determined by studying the increases in brain reward thresholds in rats (the amount of current required to receive to electrodes implanted in the lateral hypothalamus) following ethanol injection.