With its winners and losers, politics is a lot like sports. Now biologists have the testosterone—or lack thereof—to prove it. Specifically, they have found that male voters who back a losing candidate experience a drop in the hormone.

Immediately before and after the 2008 U.S. presidential election result, neuroscientists from Duke University and the University of Michigan at Ann Arbor collected the saliva of 163 college-age participants to determine the amount of testosterone in their systems. Male voters for winner Barack Obama had stable levels of testosterone, but the hormone rapidly declined in males who cast ballots for losers John McCain and Robert Barr. Female voters showed no significant testosterone changes after victory or defeat of their candidate.

Past research has shown that winning and losing in sports matches and other competitions affect testosterone levels in men. The new findings, published online October 21 by PLoS ONE, reveal that politics can influence testosterone in men “just as if they directly engaged head to head in a contest for dominance,” says Kevin LaBar of Duke, the study’s senior researcher.

In separate work, anthropologist Coren Apicella of Harvard University and her colleagues obtained similar results with a smaller group, findings they will publish this year. “It’s an exciting time for people who study political behavior, where biological factors have largely been ignored,” she notes. “Political scientists are starting to recognize the role of biology, and more and more research is showing there may be some reciprocal interactions between how elections make one feel and how feelings can affect political behavior.”

Testosterone is linked to aggression, risk taking and responses to threats. Bumps and drops in testosterone levels after competition can help both winners and losers in all species, explains Steven Stanton, the Duke study’s lead author. Victors may get motivated to pursue further gains, whereas also-rans are encouraged to back down so as not to press onward and potentially get injured. Indeed, in the Duke study, McCain and Barr voters reported feeling significantly more controlled, submissive, unhappy and unpleasant after the loss than the Obama supporters did.

The team conjectures that because the shift in the hierarchy of dominance in the nation after a presidential election is stable for at least four years, the stress of having one’s political party lose executive control could plausibly lead to continued testosterone suppression in males. But “it’s hard to know how long-lasting these effects might be,” LaBar remarks, considering that many factors influence testosterone levels.

LaBar and his team, though, are shifting gears. “We’re now going to try and explore this in spectator sports,” he says. “Sports competitions are not like the political process, where you can have a direct influence on the outcome, but obviously avid sports fans are highly invested personally in the outcome of a game.”

Note: This story was originally printed with the title "Machismo Mayhem"