The regions of the brain that respond to physical pain overlap those that react to social rejection, according to a study that used brain imaging on people involved in romantic break-ups.

''These results give new meaning to the idea that rejection 'hurts','' write a psychology professor, Ethan Kross, from the University of Michigan, and his colleagues. Their findings are reported in yesterday's issue of Proceedings of the National Academy of Sciences.

The report's co-author, Edward Smith, from Columbia University, said the research shows that psychological or social events can affect regions of the brain that scientists thought were dedicated to physical pain.

In a way, the scientists are saying ''it's not a metaphor'', Professor Smith said.

The study involved 40 volunteers who went through an unwanted break-up in the previous six months and who said thinking about the break-up caused them to feel rejected.

Functional MRIs were used to study the brains in four situations: when viewing a photo of the ex-partner and thinking of the break-up; when viewing a photo of a friend and thinking of a positive experience with that person; when a device placed on their arm produced a comforting warmth, and when that device became hot enough to cause pain, but no physical damage.

The two negative situations - thinking about the loss of a partner and the burn - caused response in the overlapping parts of the brain, the study found.

Previous studies had not shown a relationship between physical and emotional pain but those had used a less dramatic event, such as simply being told someone does not like you, Professor Smith said.

In this case, the volunteers were people who actually had been rejected and were still feeling it, he said.

There is evidence that emotional stress, such as the loss of a loved one, can affect people physically, and Professor Smith said studies such as this may help researchers devise ways to help people who are sensitive to loss or rejection.

Associated Press