The exact number of injuries resulting from the attacks is not known. Data from the aftermath show that thousands of people were treated in hospitals after the attacks. Some sustained serious physical injuries such as burns, eye injuries, and respiratory problems. But exact figures on the number and extent of injuries could not be gathered, partly because some had chosen not to receive medical treatment or had received it later. According to a September 2004 report by the U.S. Government Accountability Office (GAO), “A multitude of physical and mental health effects have been reported in the years since the terrorist attack on the World Trade Center on September 11, 2001, but the full health impact of the attack is unknown. Concern about potential long-term effects on people affected by the attack remains.” The report cites several injury categories including respiratory health, reproductive health, and mental health. Post-traumatic stress disorder (PTSD) alone was thought to have affected a great number of New Yorkers, particularly emergency responders and children. According to the report, “PTSD is an often debilitating and potentially chronic disorder that can develop after experiencing or witnessing a traumatic event. It includes such symptoms as difficulty sleeping, irritability or anger, detachment or estrangement, poor concentration, distressing dreams, intrusive memories and images, and avoidance of reminders of the trauma.” Mental health specialists reported that people across the nation demonstrated symptoms consistent with PTSD after the 9/11 attacks.