Forgive and Let Live; Revenge is sweet, but letting go of anger at those who wronged you is a smart route to good health.(Cover Story)

Of all the extraordinary events in the life of John Paul II, few can compare with the 21 minutes he spent in a white-walled cell in Rome's Rebibia prison. Just after Christmas, 1983, the pope visited Mehmet Ali Agca, the man who 30 months earlier had shot him in St. Peter's Square. He presented Agca with a silver rosary, and something else as well: his forgiveness.

It requires a Christ-like forbearance to pardon a would-be assassin, of course. But how many of us are ready to forgive an unfaithful lover, a scheming colleague or even the jerk who cut into the line at Starbucks? Persistent unforgiveness is part of human nature, but it appears to work to the detriment not just of our spiritual well-being but our physical health as well. The subject is one of the hottest fields of research in clinical psychology today, with more than 1, 200 published studies, up from just 58 as recently as 1997. It even has its own foundation--A Campaign for Forgiveness Research--which sponsored a conference last year with papers on topics like "Exploring Gender Differences in Forgiveness." (The largest number of papers dealt with forgiveness in marital and romantic relationships, which seem to generate an inordinate amount of interpersonal resentment.) Dr. Dean Ornish, America's all-purpose lifestyle guru, regards forgiveness as the tofu of the soul, a healthful alternative to the red meat of anger and vengeance. "In a way," Ornish says, "the most selfish thing you can do for yourself is to forgive other people."

Research suggests that forgiveness works in at least two ways. One is by reducing the stress of the state of unforgiveness, a potent mixture of bitterness, anger, hostility, hatred, resentment and fear (of being hurt or humiliated again). These have specific physiologic consequences--such as increased blood pressure and hormonal changes--linked to cardiovascular disease, immune suppression and, possibly, impaired neurological function and memory. One study examined 20 individuals in happy relationships, matched with 20 in troubled relationships. The latter had higher baseline levels of cortisol, a hormone associated with impaired immune function--which shot up even further when they were asked to think about their relationships. "It ...