The Boston Marathon bombings may have left local children and teens with post-traumatic stress disorder (PTSD).

 A survey found that 11 percent of children who were at the finish line on the day of the bombings showed symptoms of PTSD, NBC News reported. This statistic is six times higher than in children who were not at the scene.

"There was an enormous mental health toll associated with direct exposure," Jonathan S. Comer, a child trauma expert who led the research, told NBC News. "And there also was a toll with kids exposed to the manhunt, which was an unfolding and uncontained situation that lasted much longer than the bombing itself."

A research team also found that the more exposure local children and teens had to media coverage of the event and subsequent manhunt were more likely to experience symptoms of PTSD. To make their findings the researchers surveyed 460 parents of children who lived within 25 miles of the marathon.

The kids in the study watched an average of 1.5 hours of coverage and about 20 percent watched three hours, Time reported.

"Two thirds of the parents did not attempt to restrict their children's viewing at all. Yet we saw after Oklahoma City and 911 that TV exposure can have negative mental health effects on children, both near and far," psychologist Jonathan Comer, formerly of Boston University and now at Florida International University, told Time.

The Boston Marathon bombing left three people dead and one million Boston-area residents were put under shelter-in-place orders following the event. The researchers don't believe the shelter-in-place orders were associated with PTSD, but direct exposure such as manhunt activity in their home did, NBC News reported.

Children who were exposed to manhunt activities often exhibited behaviors such as "emotional disturbances, acting-out behaviors, trouble with hyperactivity and paying attention and conflicts with peers," NBC News reported.

"This article is a significant contribution to our understanding of the impact of terror attacks," James Halpern, director of the Institute for Disaster Mental Health at the State University of New York Paltz, told NBC News. "This study also reminds us that although children who are directly exposed are most at risk, we need to pay attention to children in the neighborhood, in nearby schools - those with less direct exposure."