New research shows that people who were not directly affected by the 9/11 terrorist attacks still experienced measurable distress as a result of the tragedy.

A recent study published in the Journal of Traumatic Stress found that people with no direct contact or connection to 9/11 victims demonstrated mild symptoms of post-traumatic stress disorder when shown images of the attacks. Thirty-one undergraduate students in Boston were surveyed for the study less than a week after Sept. 11, 2001 and reported that they felt none to moderate levels of stress due to the 9/11 events.

Researcher and Rackham student Ivy Tso said subjects were shown 90 images: 30 pictures of the 9/11 attacks, 30 negative pictures of other tragedies or conflicts and 30 pictures considered neutral. The participants then rated their levels of stimulation while an EEG recorded their brain signals as they viewed the images.

“We measure electrical signals on the scalp, and when we get a stable signal we can tell from the timing and amplitude of the brain waves what is going on psychologically,” Tso said.

After analyzing the EEG data and the participants’ subjective ratings on their levels of stimulation, Tso and the research team found positive correlations revealing mild symptoms, such as diminished attention, hyper-vigilance and suppression of unwanted thoughts, commonly associated with PTSD

Subjects who reported higher levels of distress in response to the 9/11 pictures also had brain waves with very high amplitudes — a reaction is also known as hyper-vigilance. According to Tso, this is a common symptom of PTSD, though participants in the study experienced it at a much lower level than patients with clinical cases of PTSD.

Because the subjects demonstrated these symptoms, which are not severe enough to be considered clinical PTSD, Tso and her team have begun to rethink how people are treated and diagnosed for PTSD. Rather than having normal versus clinical categories of PTSD, Tso said that it should be measured on a continuum.

Tso said she has no plans to conduct another similar study but would like to see if the results would reappear in the future.

“It would be interesting to follow up these individuals to see if they’re showing these same patterns 10 years later or is it just their dispositions,” she said.

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