A new study likens post-traumatic stress disorder in World Trade Center rescue and recovery workers to that of U.S. war veterans returning from Afghanistan.

The findings are published in the journal Environmental Health Perspectives.

The study found that the many trade center workers suffered chronic impairment of mental health and social functioning, as well as psychological distress levels that substantially exceeded population norms.

Its authors say the findings underscore a need for long-term mental health screening and surveillance, and continued treatment for the workers and their families.

Questionnaires were filled out by 10,132 workers. The authors say nearly 9 percent met criteria for depression, 5 percent for panic disorders, 62 percent for "substantial stress reaction," and 11 percent for post-traumatic stress disorder.