Background

Peer groups identified through the Internet have played an important role in facilitating school shootings. The aim of the present study was to determine whether the adolescents who had expressed a school massacre threat online differed from those who had expressed one offline. Methods

A nationwide explorative study was conducted on a group of 77 13- to 18-year-old adolescents sent for adolescent psychiatric evaluation between November 2007 and June 2009 by their general practitioners because they had threatened to carry out a school massacre. According to the referrals and medical files, 17 adolescents expressed the threat online and 60 did so offline. Results

The adolescents who expressed their threats online were more likely to be bullied and depressed, had more often pronounced the threat with clear intention and had more often made preparations to carry out the act. In contrast, the adolescents who expressed their threats offline were more likely to have problems with impulse control and had showed delinquent behavior prior to the massacre threats. Conclusions

The Finnish adolescents who expressed their massacre threats online could be considered a riskier group than the group who expressed the threats offline. Further studies with larger sample sizes are needed to elucidate this important topic. Keywords: School massacre threat; School shootings; Adolescence; Internet; Online; Violent ideation