A nationwide longitudinal study of psychological responses to the September 11 attacks was conducted on a national probability sample of 3496 adults. The study aimed to examine how demographic factors, mental and physical health history, lifetime exposure to stressful events, September 11-related experiences, and coping strategies predicted psychological outcomes over time. Surveys were conducted at 9-23 days, 2 months, and 6 months after the attacks. The study found that 17% of the US population outside New York City reported symptoms of September 11-related posttraumatic stress 2 months after the attacks, with 5.8% reporting symptoms at 6 months. High levels of posttraumatic stress symptoms were associated with female sex, marital separation, pre-September 11 physician-diagnosed depression or anxiety disorder, physical illness, severity of exposure to the attacks, and early disengagement from coping efforts. Global distress was also associated with severity of loss due to the attacks and early coping strategies. The study concluded that the psychological effects of a major national trauma are not limited to those who experience it directly, and the degree of response is not predicted simply by objective measures of exposure to or loss from the trauma. Instead, the use of specific coping strategies shortly after an event is associated with symptoms over time. In particular, disengaging from coping efforts can signal the likelihood of psychological difficulties up to 6 months after a trauma. The study also found that active coping was the only strategy that appeared to be protective against ongoing distress. The findings suggest that individuals who report such responses may be at particular risk for subsequent difficulties. The study highlights the importance of understanding the psychological effects of major national traumas and the need for targeted interventions to address the mental health needs of affected individuals.A nationwide longitudinal study of psychological responses to the September 11 attacks was conducted on a national probability sample of 3496 adults. The study aimed to examine how demographic factors, mental and physical health history, lifetime exposure to stressful events, September 11-related experiences, and coping strategies predicted psychological outcomes over time. Surveys were conducted at 9-23 days, 2 months, and 6 months after the attacks. The study found that 17% of the US population outside New York City reported symptoms of September 11-related posttraumatic stress 2 months after the attacks, with 5.8% reporting symptoms at 6 months. High levels of posttraumatic stress symptoms were associated with female sex, marital separation, pre-September 11 physician-diagnosed depression or anxiety disorder, physical illness, severity of exposure to the attacks, and early disengagement from coping efforts. Global distress was also associated with severity of loss due to the attacks and early coping strategies. The study concluded that the psychological effects of a major national trauma are not limited to those who experience it directly, and the degree of response is not predicted simply by objective measures of exposure to or loss from the trauma. Instead, the use of specific coping strategies shortly after an event is associated with symptoms over time. In particular, disengaging from coping efforts can signal the likelihood of psychological difficulties up to 6 months after a trauma. The study also found that active coping was the only strategy that appeared to be protective against ongoing distress. The findings suggest that individuals who report such responses may be at particular risk for subsequent difficulties. The study highlights the importance of understanding the psychological effects of major national traumas and the need for targeted interventions to address the mental health needs of affected individuals.