It has long been assumed that ardent sports fans derive excitement and a sense of community from rooting for a big-time team. But a growing body of scientific evidence suggests that for some fans, the ties go much deeper.

Some researchers have found that fervent fans become so tied to their teams that they experience hormonal surges and other physiological changes while watching games, much as the athletes do.

The self-esteem of some male and female fans also rises and falls with a game's outcome, with losses affecting their optimism about everything from getting a date to winning at darts, one study showed.

Science is still grappling with many questions about why people form such deep ties to sports teams, and it has not yet rigorously confronted what may be the core question: is avidly rooting for a team good or bad for someone's health? But there are early clues, some of them surprising.