Guys, if your team wins during the Final Four, the World Series or the Super Bowl, you're better off if it was a blowout, a yawner, a lopsided squelch of a contest.
Otherwise, your spiking testosterone is likely to get you into trouble -- big trouble, from joining a riot to getting into a fatal car crash.
Scientists at North Carolina State University and the University of South Carolina crunched numbers on traffic fatalities following 271 college and pro games between 2001 and 2008, looking both at the area where the game was played and the hometowns of the winning and losing teams.
They also used an independent panel of sports mavens to rate how close each game was on a scale of 1 to 5, with 1 being a blowout and 5 a cliffhanger.
They found that the closer the game, the more fatal accidents there were at the competition site and in the winning team's hometown, if that was different. Each increase in the game's closeness rating amounted to a 21 percent increase in fatal accidents at the game site, so that there were 133 percent more fatal accidents after a nail-biter than following a one-sided game.
For male athletes on the court or field, earlier research has shown that a testosterone rush accompanies victory.
"During a close game, testosterone increases for the fans as well as the players,'' said Stacy Wood, a professor of marketing at NC State and lead author of the study, to be published in a consumer research journal later this year.
"After the game, testosterone levels drop for the losing side, but spike for the winning side. Because testosterone is linked to aggressive behavior and potentially aggressive driving, we hypothesize that this may play a role in the increased number of traffic fatalities in areas with a high proportion of winning fans."
Another connection to winning and testosterone was shown in a study published in January's Journal of Strength and Conditioning Research. Andrew Fry, a researcher at the University of Kansas in Lawrence, looked at hormone levels in blood samples taken from members of a top college wrestling team.
Among both match winners and losers, testosterone levels were higher after a bout than before, but the levels among winners rose at a clip that was around 67 percent greater than among the losers.
Other studies going back to at least 1998 have shown that winning teams' male players and fans can have testosterone spikes of 20 percent or more, while levels in losers drop by about 20 percent. The few studies that have included women did not show a similar impact on their hormone levels.
The phenomenon extends to competitions of all sorts, from chess and mergers and acquisitions to politics. One recent study by scientists at Duke University and the University of Michigan showed that young male voters who backed a losing presidential candidate in the 2008 race experienced a 20-point drop between the time polls closed and when the contest was called.
In contrast, spit samples revealed that young men who had voted for Barack Obama had stable or slightly elevated testosterone levels through the evening -- levels normally decline slightly in men during the night.
The ingredients for aggression are even higher-octane when sporting events serve alcohol. A January report in the journal Alcoholism: Clinical and Experimental Research gave a likely conservative finding that 40 percent of fans leaving professional football and baseball events blew positive on a breathalyzer, and 8 percent were legally drunk.
University of Minnesota researcher Darin Erickson and colleagues had to work 13 baseball games and three football games to come up with 362 adult fans that would agree to the test -- they got a lot of refusals.
"But if we assume that it represents individuals attending professional events, it means that on average about 5,000 attendees leaving one NFL event would be above the legal blood alcohol content limit for driving,'' Erickson said.