Summary: Children who repeatedly bullied peers at age 8–9 are more likely to be suspected of violent offenses by age 31, according to a Finnish nationwide birth cohort study.
Source: University of Turku
Key finding: In a large longitudinal study from Finland, children identified as frequent bullies at 8–9 years old showed a substantially higher risk of being suspected of violent offenses in adulthood, up to age 31. This pattern persisted after accounting for family background, parental education, family structure, and early signs of child psychopathology.
The study found that both boys and girls who frequently engaged in bullying had an elevated hazard of later violent offending compared with peers who never bullied. For boys, frequent bullying was associated with particularly pronounced risk: their adjusted hazard ratio for committing severe violent offenses—such as homicide or aggravated assault—was nearly three times that of boys who had not bullied. Boys who bullied frequently also had higher odds of violent offenses than boys who bullied only sometimes. In contrast, being a victim of bullying in childhood was not linked to an increased risk of committing violent offenses in adulthood.
The researchers examined whether socioeconomic factors or early mental health problems could explain the link between childhood bullying and later violent criminality. They controlled for parental education level, family structure, and measures of possible child psychopathology. Even after adjusting for these background variables—and for whether the bully had also been a victim—the association between frequent bullying at age 8–9 and later violent offending remained significant.
These results reinforce the concept that early aggressive behavior toward peers can be an important marker of later risk and that preventing bullying in childhood may contribute to reductions in violent crime in adulthood. “Our study showed an association between bullying and violent offenses both in men and women. These findings further confirm the previous notions that preventing bullying could possibly decrease violent offenses,” said researcher Elina Tiiri from the Research Center for Child Psychiatry at the University of Turku.
Why this research matters
This investigation is part of a broader research program exploring how childhood psychosocial problems relate to adult outcomes including mental health disorders, substance misuse, mortality, self-harm, criminality, and social marginalization. By identifying early behavioral risk factors that predict serious adverse outcomes, the research aims to inform development of targeted early interventions, prevention efforts, and service planning.
Professor Andre Sourander, also from the University of Turku, emphasized the practical value of these findings: “The research project produces knowledge that helps us develop services, early interventions, and prevention.”
The study used comprehensive, population-based epidemiological data collected in Finland. Initial assessments were completed in 1989 when participants were 8–9 years old. When cohort members reached 30–31 years of age, researchers obtained records of violent offense suspicions from the Finnish National Police Register to examine long-term outcomes. The published study included approximately 5,400 participants.
About this violence and psychology research news
Author: Press Office
Source: University of Turku
Contact: Press Office – University of Turku
Image: The image is in the public domain
Original Research (open access): “Bullying at 8 years and violent offenses by 31 years: the Finnish nationwide 1981 birth cohort study” by Elina Tiiri et al., published in European Child & Adolescent Psychiatry. The study reports analyses linking bullying behavior at age 8 to later violent offense suspicions in a national cohort.
Abstract (summary)
Bullying at 8 years and violent offenses by 31 years: the Finnish nationwide 1981 birth cohort study
This population-based longitudinal study examined associations between bullying behavior and victimization at age 8 and suspected violent offenses up to age 31. In 1989, data were collected from 5,813 eight-year-old children (with low attrition), their parents, and teachers about bullying behavior. Follow-up information on violent-offense suspicions was retrieved from the Finnish National Police Register for 5,405 participants when they were aged 15–31.
Analyses were stratified by sex and categorized bullying involvement by frequency. Violent offenses were classified by severity. Cox regression models estimated hazard ratios (HRs) with 95% confidence intervals (CIs), adjusting for potential confounders including parental education, family structure, and child psychopathology, as well as for the child’s experience of victimization.
Compared with males who did not bully at age 8, frequent male bullies had a higher hazard for any violent offense (adjusted HR 3.01, 95% CI 2.11–4.33) and for severe violent offenses (adjusted HR 2.86, 95% CI 1.07–7.59). Frequent female bullies also showed increased hazard for violent offenses (adjusted HR 5.27, 95% CI 1.51–18.40). Being a victim of bullying was not associated with later violent offending. The findings suggest that preventing childhood bullying could reduce violent offenses across both sexes.