Regret is as old as conscience itself, a staple of Bible stories and barroom confessions through the ages. Yet only recently have researchers begun to clarify its emotional impact and learn how it affects our health and behavior.

“Especially after middle age, regret can become a very powerful factor in the way people think about themselves,” said Dr. William Callahan, an Irvine, Calif., psychiatrist. “I hear it all the time: ‘I never got close to my children’ or ‘I promised myself I’d never be the reincarnation of my father, and I’ve become him.’ “

It is the larger self-betrayals that permanently crimp our narrative tape: a marriage ended too soon, or too late; an educational degree left unfinished; a move across the country, away from aging parents.

“Imagining what might have been is usually healthy; it’s one way we learn from the past,” said Neal Roese, an associate professor of psychology at the University of Illinois in Urbana-Champaign who studies how thoughts like regret influence behavior.

“But there’s a big difference when something awful happens and we cannot repair it. That’s when we can get stuck in the negative emotions of serious regret.”

Some people swimming in self-blame are likely making themselves ill. Preliminary evidence from an ongoing study of 120 older men and women suggests that serious regrets are associated with physical symptoms, such as migraine headaches and gastrointestinal problems, according to Carsten Wrosch, a researcher at Concordia University in Montreal.

In a study published in June, Wrosch and Jutta Heckhausen, a psychologist at the University of California at Irvine, reported that the specific way we think about our regrets can significantly affect our emotional well-being.

The healthiest approach varies with age, they found. The pair administered questionnaires on regret and mental health to 122 adults ranging in age from 20 to 87.

Younger adults who scored high on measures of mental health tended to blame themselves for the behavior they regretted; they assumed they had full control of the situation.

In contrast, older adults scoring high on the tests were more likely to give themselves a break.