Youth today live their lives increasingly online. The Internet provides opportunities for self-expression, hobbies, and socializing with friends. With the rapid development of social media, adolescent peer groups have become computer-mediated, and these online groups are becoming an additional source of identity [1, 2]. According to EU Kids Online, 82% of European youth aged 15–16 had a profile on a social networking site, such as Facebook in 2010 . Because their lives become increasingly computer-mediated, these young people are also expressing various concerns via online behavior. In particular, youth who face problems offline are more likely to engage in risky online behavior [4, 5].
Current research on youth and the Internet emphasizes the co-existence of opportunities and risks [3, 6]. Concerns include cyberbullying and sexual harassment as well as solicitation online [7–11]. The Internet provides easy access to controversial and violent material. Visiting the “snuff” sites (portraying actual murders or deaths by people), for example, is considered a developmental risk . Furthermore, various kinds of harmful or risky online communities, including pro-self-harm and pro-suicide websites, have proliferated [13–16]. Even extremely shocking and rare events such as school shootings have become objects of fascination for some youth, and the Internet makes it easier to find others with similar radical and deviant opinions [17–19].
Peer groups identified through the Internet have played an important role in facilitating school shootings. In Finland, two school shootings took place in November 2007 and September 2008 and became the most lethal mass murder cases in the criminal history of Finland. Both offenders were young males who idealized earlier American and German shooters and used the Internet to document their positive thoughts and ideas about violence as well as videos and statements about their future intentions. Both of the shooters were active in pro-school-shooting online communities, which supported their fantasies of violent revenge. Interestingly, neither of the Finnish school shooters found any encouragement for their intentions from their offline peer groups. Rather, both Finnish and international online groups did support their ideas .
It is possible that the online world enables the violent and suicidal ideation for some adolescents. Such behavior is more likely to occur when adolescents are already experiencing problems in their daily offline world [4, 5]. Even so, one should not be underestimate the relevance of the online world. Group pressures, for example, may be even stronger in a computer-mediated setting than face-to-face . Thus, deviant online communities, such as pro-school-shooting groups, may be able to reinforce the violent ideation. The Internet and social media mostly serve as tools; finding other like-minded people is easier in the online world.
Because school shooters have called themselves “rebels”, they have become objects of admiration for some young people, especially after the Columbine shootings in the United States in 1999 [22–24]. School shooters have cultivated images of martyrdom and political revolt against oppressors . Such romanticized images may make school shooters rebels in the eyes of young people troubled by experiences of bullying at school and with psychological problems which magnify the seriousness of these experiences. For some young people, school shooters have become heroes, and authors have speculated that committing a school shooting threat in particular becomes a way to show sympathy and admiration for the school shootings . After dramatic violence, threats of similar acts are likely to occur. Threats peaked, for example, after both the Columbine massacre in the US (1999)  and the Winnenden tragedy in Germany (2009) . The Internet likely facilitates the expression of such acts.
Before the Jokela school shooting tragedy in November 2007, threats to carry out a massacre warranting a police investigation were rare, with about 5–10 threats per year, as continues to occur in the other Nordic countries. Immediately after the school shooting in November 2007, 87 police registered threats, and within a few weeks of the second school shooting in September 2008, more than a hundred new threats were communicated. Still, in 2011, the annual number of threat was nearly 60 cases (police statistics, personal communication from Savolainen, M.).
Referrals to adolescent psychiatric services due to threats of school massacres peaked in Finland after the Jokela and Kauhajoki school shootings. Through the chief adolescent psychiatrists responsible for specialist-level adolescent psychiatric services in the different hospital districts in Finland, we identified all 77 adolescents aged 13–18 who underwent adolescent psychiatric assessment for having expressed threats of a school massacre after the two incidents . Of them, 17 had expressed the massacre threat online.
In the field of adolescent psychiatry, studies focusing on links between the Internet, adolescent mental health problems and antisocial behavior remain scarce. The aim of the present study was to determine whether the Finnish adolescents who had expressed a school massacre threat online differed from those who had expressed one offline. The focus was on current psychiatric symptoms and clinical diagnoses as well as on adverse family life events, mental health contacts, academic performance and delinquency prior to the threat. We investigated any adolescents` experiences of being bullied at school prior to the threat. We also evaluated the characteristics of the index threat as well as the risk posed by the adolescent.