Mass shootings are contagious: US study

Mass killings and school shootings appear to be contagious, according to a new US study which found that such tragedies could inspire similar events in the near future.
Sherry Towers, an Arizona State University research professor, and colleagues were prompted in January 2014 to study whether mass shootings inspire each other.
Towers was at Purdue University in Indiana for a meeting on January 21, 2014 when there was a shooting in a neighbouring university building. A 21-year-old student named Andrew Boldt was shot and then stabbed by another student.
Recalling three other school shootings that had made the news in the prior week, she wondered if the string of tragedies was more than coincidental.

"I wondered if it was just a statistical fluke, or if somehow through news media those events were sometimes planting unconscious ideation in vulnerable people for a short time after each event," she said.
The researchers examined databases on past high-profile mass killings and school shootings in the US and fit a contagion model to the data to determine whether these tragedies inspired similar events in the near future.

They determined that mass killings - events with four or more deaths - and school shootings create a period of contagion that lasts an average of 13 days.
Roughly 20 to 30 per cent of such tragedies appear to arise from contagion, researchers said.

The researchers knew that previous studies have shown that suicide in youths can be contagious, where one suicide in a school appears to spark the idea in other vulnerable youths to do the same.
"It occurred to us that mass killings and school shootings that attract attention in the national news media can potentially do the same thing, but at a larger scale," Towers said.
"While we can never determine which particular shootings were inspired by unconscious ideation, this analysis helps us understand aspects of the complex dynamics that can underlie these events," Towers said.
On average, mass killings involving firearms occur approximately every two weeks in the US, and school shootings occur on average monthly, researchers said.

The team found that the incidence of these tragedies is significantly higher in states with a high prevalence of firearm ownership.
The study was published in the journal PLoS ONE.