According to researchers at the U.S. Centers for Disease Control and Prevention, people caught in the cloud of dust and debris caused by the collapse of several buildings have more chances of suffering from psychological trauma and breathing problems because they were around the September 11 attack. "The trauma of being caught in the cloud itself, the whole experience had an impact on their … psychological health later on," said Dr. Robert M. Brackbill, a doctor from an organization that has been tracking the health of more than 71,000 people who worked at ground zero or were in the area on Sept. 11. The present study interviewed 8,418 adults who escaped from the attacks, the interviews taking place between Sept. 5, 2003 and Nov. 20, 2004 and did not involve any medical examination. The study suggested that about 60% of the people caught in the cloud which covered the area were 3 times more likely to have respiratory problems, while 40% have a higher chance of having severe psychological problems and 5 times more likely to report a stroke. More than 56% of survivors had new respiratory problems or the old ones have worsened and more than 43% suffered a physical injury in the incident, the most common being at the eye. More than 64% of the survivors said they were depressed, anxious or had other emotional problems and 11% were in severe psychological distress at the time of their interview, the study said. Officials say that they will need 20 years or more to see if exposure to the 9/11 incident will lead to cancer and other kinds of illnesses.