A majority of survivors of the 2001 attacks that destroyed the World Trade Center suffered from respiratory ailments and depression, anxiety and other psychological problems up to three years later, federal health officials said Friday.

People run from the collapse of the World Trade Center Towers in New York in this Tuesday, Sept. 11, 2001, file photo. [AP Photo]

The people who escaped from collapsed or damaged buildings on Sept. 11, 2001, were several times as likely to suffer from breathing problems or psychological trauma if they were caught in the cloud of trade center dust and debris that covered lower Manhattan, researchers at the U.S. Centers for Disease Control and Prevention said.

"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 CDC doctor working with the World Trade Center Health Registry, which has been tracking the health of more than 71,000 people who worked at ground zero or were in the area on Sept. 11.

Friday's study drew from preliminary interviews with 8,418 adults in the registry who escaped from the twin towers, the collapsed Seven World Trade Center and more than 30 buildings that suffered extensive damage on Sept. 11. More than 70 percent escaped from the twin towers.

The interviews took place more than two years after the attacks, between Sept. 5, 2003, and Nov. 20, 2004, and did not involve medical examinations. Follow-up surveys are planned this month.

"We are just beginning to learn about the health effects of the worst day in New York City's history," said Daniel Slippen, a survivor of the attacks and a member of the registry's community advisory board. "It is critical to know whether these physical and mental effects will continue, diminish or grow worse over time."

City officials in charge of the registry say it will likely take 20 years or more to determine whether 9/11 exposure led to increased cancer deaths or illnesses among survivors.

The study said more than six in 10 were caught in the clouds of trade center dust that enveloped the area. Those people were nearly three times as likely to have respiratory problems, 40 percent more likely to experience severe psychological problems and five times more likely to report suffering a stroke, Brackbill said.

More than 56 percent of the survivors said they had new or worsening respiratory ailments, including sinus problems, shortness of breath and a persistent cough. More than 43 percent sustained a physical injury on Sept. 11; the most common were eye injuries.

Almost all of the people studied witnessed at least three events likely to cause psychological trauma, such as the collapse of the towers, the deaths or injuries of others or people jumping from the twin towers, the study said.

More than 64 percent of the survivors said they were depressed, anxious or had other emotional problems, and nearly 11 percent were in severe psychological distress at the time of their interview, the study said.