Whisky produces a bad hangover
Drinking whisky will result in a worse hangover than vodka, according to research by US scientists.
The reason might lie in the number of molecules called "congeners" which it contains compared to vodka, the Brown University team said.
But the study also suggested that sticking to vodka all night rather than whisky would not improve your performance at work the next day.
The study is published in Alcoholism: Clinical and Experimental Research.
The 95 volunteers for the research, all healthy alcohol users, had one night of "acclimatisation" before drinking either whisky or vodka the following night.
They were given enough alcohol to put them a third over the legal driving limit for the UK.
On the third night they were given a "placebo" drink containing no alcohol.
On each occasion, they were then asked how they felt the following day, and were tested on how well they could concentrate on tasks.
The volunteers who drank whisky reported far more hangover symptoms such as headache nausea, thirst and fatigue compared with those who drank vodka.
However, the overall performance at the concentration task was roughly the same between the two groups.
Professor Damaris Rohsenow, who led the research at Brown University in Rhode Island, said: "While people felt worse, they didn't perform worse after bourbon (a type of whiskey made in the US) than after vodka."
He said that the study also showed that workers in "safety-sensitive" roles could be impaired by drinking - long after the alcohol itself had disappeared from the bloodstream.
The study, which also monitored sleeping patterns in the volunteers, found that disrupted sleep was no worse in either group.
The reason why whisky might cause more unpleasant hangovers might lie in the number of molecules called "congeners" which it contains compared to vodka, said Professor Rohsenow.
These include small amounts of chemicals such as acetone, acetaldehyde and tannins.
Chris Sorek, the chief executive of charity Drinkaware, said that social drinkers should be aware that no alcoholic drink removed the risk of a hangover.
He said: "Christmas is a time to socialise and celebrate, but many people will be drinking excessively - drinking too much of any alcoholic drink can have a number of undesirable short and long-term effects."
While exceeding recommended daily limits might mean hangovers the following day, he said, in the long term, regular heavy drinking could increase the risk of cancer or liver disease.