Developmental Trajectories of Bullying and Associated Factors


  • We extend our appreciation to the children, adolescents, schools, and parents who participated in this research. We are indebted to Arland O’Hara, our research coordinator, and to the many graduate students and undergraduate research assistants for their contributions and dedication to the research program. This research was supported by funding from the Ontario Mental Health Foundation, the National Health Research and Development Program, the Social Sciences and Humanities Research Council of Canada, and the Canadian Institutes of Health Research: Institute of Gender and Health. The first author has been supported through a senior research fellowship from the Ontario Mental Health Foundation

concerning this article should be addressed to Debra Pepler, LaMarsh Centre for Research on Violence and Conflict Resolution, York University, 4700 Keele Street, Toronto, Ontario, Canada M3J 1P3. Electronic mail may be sent to


Trajectories in bullying through adolescence were studied along with individual, family, and peer relationship factors. At the outset, participants’ ages ranged from 10 to 14; 74% identified as European Canadian with the remainder from diverse backgrounds. With 8 waves of data over 7 years, 871 students (466 girls and 405 boys) were studied to reveal 4 trajectories: 9.9% reported consistently high levels of bullying, 13.4% reported early moderate levels desisting to almost no bullying at the end of high school, 35.1% reported consistently moderate levels, and 41.6% almost never reported bullying. Students who bullied had elevated risks in individual, parent, and peer relationship domains. Risk profiles and trajectories provide direction for interventions to curtail the development of power and aggression in relationships.