As millions continue to cope with the aftermath of September 11th's tragedy and horror, four studies in major health and medical journals have found significant levels of increased stress and cases of Post Traumatic Stress Disorder (PTSD) across the nation — offering empirical evidence that the terrorist attacks have had real and profound effects, even for those who were not physically impacted.

The most recent of the three studies, "Posttraumatic Stress Disorder in Manhattan After the September 11th Terrorist Attacks," found that more than half of those surveyed reported at least one PTSD symptom, including intrusive memories or loss of sleep. The study, published in the September issue of Journal of Urban Health, is based on interviews with more than 1,000 people living in Manhattan.

The study found "substantial psychological symptoms in the general population (of the area) five to eight weeks after the September 11th attacks."

In addition, findings showed that living close to the World Trade Center, low social support, prior life stressors, and being involved in rescue efforts were all significant predictors of PTSD symptoms. "Social ties, including social networks and social supports, have been shown to play a positive role in mental health," the authors noted.

A second study, published in the Aug. 7 Journal of the American Medical Association (JAMA) concluded that cases of PTSD were significantly higher in New York City than in other major metropolitan areas in the months after the September 11 terrorist attacks.

The web-based study, titled "Psychological Reactions to Terrorist Attacks," found that stress levels in other areas of the country were "within normal ranges," but that residents of New York reported significantly higher levels of PTSD symptoms one to two months after the attacks.

The study also found a correlation between TV viewing and PTSD, but lead author William Schlenger says the cause-effect relationship is complex. "We found an association between PTSD symptom levels and the number of hours of September 11 coverage people reported watching, but the direction of causality is unclear," said Schlenger.

Those findings, said Schlenger, indicate that people suffering from PTSD symptoms may have chosen television viewing as a way to deal with their feelings. "People who were distressed watched the coverage as a way of trying to cope with their distress," said Schlenger, "However, it's probably fair to hypothesize the causality works to some extent in both directions."

Two studies in the New England Journal of Medicine supported the link between the terrorist attacks and increased stress levels both in New York and nationwide. One, published in the March 28 issue, found a direct connection between witnessing the September 11 attacks and cases of PTSD in Manhattan, though the study did not specifically address exposure to media coverage. The study, titled "Psychological Sequelae of the September 11 Terrorist Attacks in New York City," was conducted by researchers at the New York Academy of Medicine.

Another New England Journal of Medicine Study, published just two months after the tragedy, found that increased stress was not limited to people in the geographical locations attacked. The national telephone survey conducted within a week of the attacks found that 90 percent of those who responded reported at least one symptom of stress.

As in the JAMA study, findings showed that television viewing could serve as a way to cope for some. But, the authors warned, "for others, particularly children, watching television may have exacerbated or caused stress, especially with repeated viewing of terrifying images."

The most common coping mechanisms, the study found, ranged from talking to others and participating in group activities to turning to religion or making donations to relief agencies.

"Americans across the country, including children, had substantial symptoms of stress," wrote the authors of the study, titled "A National Survey of Stress Reactions After the September 11, 2001 Terrorist Attacks."

"Even clinicians who practice in regions that are far from the… attacks should be prepared to assist people with trauma-related symptoms of stress," they concluded.