Contagion in mass killings and school shootings

Sherry Towers, Andres Gomez-Lievano, Maryam Khan, Anuj Mubayi, Carlos Castillo-Chavez

Research output: Contribution to journalArticle

47 Citations (Scopus)

Abstract

Background: Several past studies have found that media reports of suicides and homicides appear to subsequently increase the incidence of similar events in the community, apparently due to the coverage planting the seeds of ideation in at-risk individuals to commit similar acts. Methods: Here we explore whether or not contagion is evident in more high-profile incidents, such as school shootings and mass killings (incidents with four or more people killed). We fit a contagion model to recent data sets related to such incidents in the US, with terms that take into account the fact that a school shooting or mass murder may temporarily increase the probability of a similar event in the immediate future, by assuming an exponential decay in contagiousness after an event. Conclusions: We find significant evidence that mass killings involving firearms are incented by similar events in the immediate past. On average, this temporary increase in probability lasts 13 days, and each incident incites at least 0.30 new incidents (p = 0.0015). We also find significant evidence of contagion in school shootings, for which an incident is contagious for an average of 13 days, and incites an average of at least 0.22 new incidents (p = 0.0001). All p-values are assessed based on a likelihood ratio test comparing the likelihood of a contagion model to that of a null model with no contagion. On average, mass killings involving firearms occur approximately every two weeks in the US, while school shootings occur on average monthly. We find that state prevalence of firearm ownership is significantly associated with the state incidence of mass killings with firearms, school shootings, and mass shootings.

Original languageEnglish (US)
Article numbere0117259
JournalPLoS One
Volume10
Issue number7
DOIs
StatePublished - Jul 2 2015

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Firearms
Homicide
Seed
Ownership
planting seed
Incidence
incidence
suicide
risk groups
Suicide
ownership
Seeds
deterioration
testing

ASJC Scopus subject areas

  • Agricultural and Biological Sciences(all)
  • Biochemistry, Genetics and Molecular Biology(all)
  • Medicine(all)

Cite this

Contagion in mass killings and school shootings. / Towers, Sherry; Gomez-Lievano, Andres; Khan, Maryam; Mubayi, Anuj; Castillo-Chavez, Carlos.

In: PLoS One, Vol. 10, No. 7, e0117259, 02.07.2015.

Research output: Contribution to journalArticle

Towers, Sherry ; Gomez-Lievano, Andres ; Khan, Maryam ; Mubayi, Anuj ; Castillo-Chavez, Carlos. / Contagion in mass killings and school shootings. In: PLoS One. 2015 ; Vol. 10, No. 7.
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