LOS ANGELES — Children who are exposed to violence experience wear and tear to their DNA that is similar to that seen in aging, according to a new study that may help explain why they face a heightened risk of mental and physical disorders as adults.

In a long-term study of 118 pairs of identical twins, researchers at Duke University found that boys and girls who had experienced violence had shorter genetic structures called telomeres than youngsters who had more peaceful upbringings. The children in the former group had been physically abused by an adult or bullied frequently, or had witnessed domestic violence between the ages of 5 and 10. And the more types of violence a child had experienced, the faster his or her telomeres eroded, said study leader Idan Shalev, who published the findings Tuesday in the journal Molecular Psychiatry.

He hazarded an estimate that children who had experienced multiple types of violence had lost seven to 10 years of life.

"Kids who are raised in poverty and hardship have more disease. This might explain why," said Dr. Owen Wolkowitz, a psychiatrist at the University of California, San Francisco who has studied the link between depression and telomere length in adults.