For the study, an Internet-based survey of nearly 5,000 Americans was conducted in the two-to-four weeks after the bombing. About one percent of the respondents were present at the site of the event, an additional nine percent had someone close who was near the site, and another nine percent were directly affected by the aftermath (because of Boston’s lockdown or other such reasons).

Contrasting this subgroup’s answers with those who were exposed to the event through the media—be it television, radio, or via the Internet—gave a clear result: acute stress occurs even among those who were not directly present at the event.

What was surprising was that, if a person spent more than six daily hours exposed to bombing-related coverage, he or she was nine times more likely to report symptoms of high acute stress. It did not matter whether this person was directly exposed on the day of the event or whether the person lived in Boston or New York. While only five percent of the respondents reported suffering from those symptoms, there was a direct correlation between acute stress symptoms shown and the number of hours exposed to bombing-related media.