How Americans Are Handling Post 9/11 Trauma

Eighteen years ago, more than 60% of Americans watched as the worst terror attack ever to occur on U.S. soil unfolded on television — either in real time or in repeated replays.

That up-close view of the murders of almost 3,000 people jolted Americans out of the sense of security they'd enjoyed at least since World War II.

"I think that up until that time, perhaps people were more optimistic or certainly had a sense that it couldn't happen here. Terrorist attacks were something that happened overseas, but not in the United States on our soil," says Roxane Cohen Silver, professor of psychological science at the University of California, Irvine.

"The concept of fearing violence on a day-to-day basis just wasn't part of the existence of most people in the United States."

Cohen Silver, who studies the impact of collective trauma, says some individuals with no direct connection to the 9/11 attacks exhibited symptoms that experts had previously assumed were the result of direct exposure to trauma.

"Individuals who watched a great deal of television in the first week after 9/11 were more likely to exhibit post-traumatic stress symptomatology and physical health ailments years later," she says.

Those symptoms often included anxiety and fear, as well as the onset of physical health ailments such as cardiovascular issues.

"We learned from 9/11 that large-scale events could impact people beyond the directly affected communities, that the events that occurred in New York could impact people in Kansas," Cohen Silver says. "The second message we've learned from 9/11 was the important role of the media in transmitting that awareness and that potential anxiety."

In the 18 years since 9/11, the rise of social media and smartphones has resulted in increased access to images of mass violence. In addition, there are no news editors or other middlemen to weed out potentially disturbing content. The speed with which these images reach people has also escalated.

Young Americans born after 9/11 have grown up in a world where acts of mass violence are increasingly commonplace.

More than 230 school shootings have occurred since 1999, when 13 people were killed at Columbine High School near Denver.