Sleep Disturbance Following September 11: Results of a Nationwide Longitudinal Study

Abstract

The terrorist attacks of September 11, 2001, provided a unique, though unfortunate, opportunity to study Americans' sleep reactions to a traumatic event. Questionnaires were distributed electronically to a web-based panel whose demographic distribution closely matched current U.S. census counts. Prior to 9/11/01, participants reported whether they had ever been diagnosed with anxiety, depression, or insomnia. Two weeks following the terrorist attacks, they completed an acute stress questionnaire (SASRQ) which included questions about 9/11-related difficulty falling or staying asleep and nightmares. They later completed a posttraumatic stress symptom questionnaire at two time points: 2 months and 6 months post-9/11. This instrument, the IES-R, included questions about 9/11-related difficulty falling asleep, difficulty staying asleep, and dreams. A total of 782 adults (50.4% male; mean age = 49.6 years) responded.Two weeks following the terrorist attacks, 23% of the sample reported having 9/11-related difficulty falling or staying asleep; 9% reported 9/11-related nightmares. Two months following the attacks, 27% reported having at least some difficulty falling asleep related to 9/11, 33% reported having difficulty staying asleep, and 17% reported having 9/11-related dreams. When assessed again at 6 months post-9/11, levels of these three sleep issues dropped significantly to 14%, 15%, and 8%, respectively. Females reported higher levels of 9/11-related sleep difficulties than males both at 2 weeks and 2 months after the attacks. By 6 months post-9/11, this sex difference had all but disappeared. Older respondents were slightly less likely than younger ones to report nightmares 2 weeks post-9/11 and dreams 2 months post-9/11. Those with pre-9/11 diagnoses of anxiety, depression, and insomnia generally had higher rates of 9/11-related sleep difficulties at all time points assessed.When tested with a hierarchical regression model, difficulty falling or staying asleep at 2 weeks post-9/11 significantly predicted posttraumatic stress symptoms experienced 6 months (but not 2 months) following the attacks. This was true even when taking into account the contribution of pre-existing psychiatric diagnoses and non-sleep-related acute stress symptoms. These findings raise the possibility that the experience of disturbed sleep soon after a trauma directly contributes to the eventual development and exacerbation of posttraumatic stress symptoms.