SANTA CRUZ, Calif. (AP) _ The little Kuwaiti boy survived the Iraqi invasion of his country and was living without his father, a prisoner of war. But a recurring nightmare _ of Saddam Hussein stabbing his brother to death _ was prolonging the trauma.

One night he had a different dream: This time he carried the knife, becoming a hero who kills his nemesis.

The emotional weight he carried disappeared.

Altering recurring nightmares may hold a key to recovery for many victims of trauma, says Dr. Deidre Barrett, a professor of behavioral medicine and hypnotherapy at Harvard Medical School. Barrett spent a month in Kuwait City after the Gulf War training other therapists to treat post-traumatic stress disorder.

``Just changing something in the dream gives people such a sense of mastery in controlling things,'' says Barrett, who was in Santa Cruz last week for the annual Association for the Study of Dreams. ``Just that sort of dramatic sense of confidence he had in a dream carried over into his waking life.''

More than one in 20 adults in the United States say they have disturbing dreams, and more than twice as many children have nightmares. Trauma victims _ whether students who witnessed the Columbine High School massacre, ethnic Albanian refugees or people who have been raped or attacked _ often immediately have nightmares that recall their experience.

Later, the bad dreams may take on more frightening twists, recurring several times, researchers say.

Although the young Kuwaiti boy's dream changed spontaneously, hundreds of people have consciously reduced the frequency of recurring nightmares or eliminated them altogether, says Dr. Barry Krakow, an associate research professor at the University of New Mexico Health Sciences Center who also works for the private Center for Sleep Medicine and Nightmare Treatment.

In three different studies of a technique Krakow pioneered and presented last week, researchers found that about 100 nightmare sufferers were able to decrease the frequency of those dreams by 40 to 100 percent.

Patients were taught to create a new ``dream,'' with images they rehearsed daily and thought about before going to sleep each night as a way of breaking what for many is a nightmare habit.

``In the Western world it's a takeoff on the power of positive thinking,'' says Krakow. ``If we do something with the images, we might be able to break the habit portion. That really seems to break the dam.''