People who smoked more heavily on the day they drank reported much more severe hangovers, according to a study out of the Center for Alcohol and Addiction Studies at Brown University in Providence, Rhode Island.

"At the same number of drinks, people who smoke more that day are more likely to have a hangover and have more intense hangovers," researcher Damaris J. Rohsenow said.

What's more, just being a smoker means you're more likely to get hangovers.

The researchers aren't sure why this is the case, but believe it has something to do with the fact that nicotine receptors in the brain are connected to how much dopamine - a feel-good brain chemical - alcohol releases.

So the reason smoking makes hangovers worse is probably the same reason it makes drinking feel more fun.