(NEW YORK) -- A decade after the terrorist attacks on Sept. 11, 2001, thousands are still feeling the emotional impact.
After 9/11, a unified spirit helped Americans cope.
"There was a real sense of solidarity in the community which I think probably limited the [emotional] damage," says Dr. John Markowitz at the New York State Psychiatric Institute.
But there are nearly 4,000 people who are still suffering with 9/11-related post-traumatic stress disorder (PTSD).
"Everyone was in a certain amount of shock. For most people that subsided, but for a lot of people that's really persisted," Markowitz says.
He adds, "Every time there's another catastrophe in Japan or in Norway, wherever, it reawakens this for people."
Markowitz is spending the next two years studying PTSD and the best way to treat it.
He explains that some people try to seal off this event and avoid thinking about it, but certain things can trigger it. One such example could be the 10-year commemoration of the 9/11 attacks. While it may help some cope, it may resurface painful memories for others.
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