Unless you want to start the new year in the depths of a nauseating hangover, you should take time on the night before to consider what's in your glass. Different types of alcohol—whether it's made in a barrel from barley or bottled from grapes—are digested in distinctive ways. Our question: Which alcohol is most likely lead to a hangover?
It's a complicated issue. Everything from genetic disposition to body weight to where you live to the quantity of sleep you got last night and the amount of food in your belly plays a part in whether you'll get a hangover and how severe it may be. But according to studies conducted on the causes and consequences of hangovers and conversations with experts, there are a few constants.
One of the predictive factors is the amount of congeners in alcohol. Congeners—chemical toxins produced during fermentation and aging, or added during production via certain flavorings—have a direct effect on the nervous system. When you drink alcohol, these toxins course through your bloodstream as your liver metabolizes the alcohol.
In general, darker liquors contain more congeners and cause more severe hangovers. According to a study published in Alcoholism: Clinical and Experimental Research in March by Damaris Rohsenow at Brown University's Center for Alcohol and Addiction Studies, bourbon contains 37 times the amount of congeners as vodka. The study participants who imbibed bourbon reported more severe hangovers.
But, "congeners are only one part of the story," says Samir Zakhari, director of the division of metabolism and health effects at the National Institute of Alcohol Abuse and Alcoholism. Zakhari points to other issues such as fatigue, dehydration, and, of course, the amount of alcohol consumed that influence whether a hangover will occur and how severe it may be. A bottle of Budweiser has six times the congener content of a Long Island iced tea, but about two-thirds the amount of alcohol. That may be part of the reason why, according to a study published in Alcohol and Alcoholism in 2008 by researchers at the University of Utrecht, a person would have to drink twice as many beers compared to servings of hard alcohol to get a hangover, and the beer hangover would be half as severe.
To rank our list of the worst hangover inducers, we focused on cocktails, and considered the total alcohol and congener content of the most popular mixed drinks. To ensure accurate comparisons, all recipes were pulled from the International Bartenders Association.
Total alcohol content per drink was tabulated using alcohol by volume standards for each type and amount of alcohol in every drink. Total congener content per drink was calculated using the congener content per 100 mL of each type of alcohol according to "Congener Contents of Alcoholic Beverages," a study published in the Journal of Studies on Alcohol in 1981 by Hebe Greizerstein—the most comprehensive clinical data compiled to date. Though congener content varies by brand of alcohol in addition to type, for the purpose of comparison and according to the data available, a single brand of each alcohol was used for each recipe (meaning the congener content of 80-proof Smirnoff vodka was used to calculate congener content in all drinks which included vodka).
Total alcohol and congener content were equally weighted for each drink, and ties were broken based on which drink had a greater mix of alcohols—while studies are inconclusive, mixing your poisons is widely considered an easy way to induce a head-throbbing, body-aching morning.