The study looked at a group of 183 people in Durham and Ann Arbor. A testosterone sample was analyzed at 8 p.m., as the polls closed, and a second was taken after the results were announced around 11:30 p.m.
Researchers say a man's testosterone naturally drops slightly during the course of an evening, but the election night results were more dramatic. The levels in Obama voters didn't fall, and levels in McCain voters dropped more than they should have.
"This is a pretty powerful result," said Duke neuroscientist Kevin LaBar in a university news release. "Voters are physiologically affected by having their candidate win or lose an election."
A questionnaire given to the participants after the election showed the McCain supporters felt unhappy, submissive and more controlled than Obama supporters.
Duke said other studies have shown men who participate directly in an interpersonal contest and win often show a boost in testosterone levels while the loser's drops. This is the first time the phenomenon has been studied in voters.
Duke post-doctoral researcher Steven Stanton said it appears even vicarious participation is enough to change hormone levels.
"Voters participate in elections both directly by casting their ballots, and vicariously because they don’t personally win or lose the election," Stanton said. "This makes democratic political elections highly unique dominance contests."