Here's the scientific reason why hangovers suck and what causes them

Bucknell University neuroscientist Judy Grisel explains why hangovers are so awful and the science behind them. From TEDEd:

The molecule responsible for hangovers is ethanol, which we colloquially refer to as alcohol. Ethanol is present in all alcoholic beverages, and generally speaking, the more ethanol, the greater the potential for a hangover.