Young people who experience bullying are more likely to fantasise about committing acts of violence, a study led by a Cambridge professor suggests.
An international team of researchers tracked the self-reported thoughts and experiences of 1,465 young people from schools across the Swiss city of Zurich at the ages of 15, 17 and 20.
Participants were questioned on whether violent thoughts had occurred in the last 30 days, and the types of bullying or aggression experienced over the last 12 months.
Researchers looked at the level of aggression in fantasies, from humiliation to murder.
They also asked about 23 forms of “victimisation”, such as taunts, physical attacks and sexual harassment by peers, aggressive parenting – yelling, slapping, hitting with a belt – and dating violence, such as being pressured into sex.
Most of the participants reported that they had been victimised in at least one way.
Experiencing a range of mistreatment was “closely associated” with a higher likelihood of thinking about killing, attacking or humiliating others, according to the research.
Boys were more prone to violent thinking in general, but the effect of multiple victimisations on violent fantasies was very similar in both sexes.
Among 17-year-old boys who had not been victimised in the preceding year, the probability of violent fantasies in the last month was 56%.
With every additional type of mistreatment, the probability of violent fantasies increased by up to 8%.
Those who listed five forms of victimisation had an 85% probability of having had violent fantasies; for those who listed ten it was 97%.
Among girls the same age, no victimisation experience had a violent fantasy probability of 23%, which increased to 59% in those who listed five types of mistreatment, and 73% in those who said they had suffered 10.
The study did not examine whether violent ideations caused by victimisation actually lead to violent behaviour.
Prof Manuel Eisner, director of Cambridge’s Violence Research Centre and lead author of the study, said: “One way to think about fantasies is as our brain rehearsing future scenarios.
“The increased violent fantasies among those who experience bullying or mistreatment may be a psychological mechanism to help prepare them for violence to come.
“These fantasies of hitting back at others may have roots deep in human history, from a time when societies were much more violent, and retribution – or the threat of it – was an important form of protection.”
According to Prof Eisner, the research hints at the extent of violent ideation in societies as seemingly peaceful as Switzerland, with murderous thoughts surprisingly commonplace.
“About 25% of all 17-year-old boys and 13% of girls reported having at least one fantasy of killing a person they know during the past 30 days,” he said. “Close to one in five of all the study participants at that age.
“These thoughts may be deeply troubling to those who experience them.”
The study suggested that socio-economic status played little role in violent fantasy rates, and “adverse life events” such as financial troubles or parental separation also had no significant impact.
Prof Eisner said: “Thoughts of killing others are triggered by experiences of interpersonal harm-doing, attacks on our personal identity, rather than noxious stimuli more generally.
“It’s the difference between conditions that make people angry and upset, and those that make people vengeful.”
By following most of the teenagers to the cusp of adulthood, researchers could track patterns over several years.
Overall rates of the most extreme thoughts decreased by the age of 20 – only 14% of young men and 5.5% of women had thought about killing someone they know in the past month.
The study is published in the journal Aggressive Behavior.