William E. Copeland, Ph.D., associate professor of psychiatry and behavioral sciences at Duke University School of Medicine and the study's lead author, and his colleagues used data from the Great Smoky Mountains Study, a robust, population-based study that has gathered information on 1,420 individuals for more than 20 years. Individuals were randomly selected to participate in the prospective study, and therefore were not at a higher risk of mental illness or being bullied.
Participants were interviewed throughout childhood, adolescence and young adulthood, and among other topics, were asked about their experiences with bullying.
The researchers also collected small blood samples to look at biological factors. Using the blood samples, the researchers measured C-reactive protein (CRP), a marker of low-grade inflammation and a risk factor for health problems including metabolic syndrome and cardiovascular disease.
Three groups of participants were analyzed: victims of bullying, those who were both bullies and victims, and those who were purely bullies. Although CRP levels rose for all groups as they entered adulthood, victims of childhood bullying had much higher CRP levels as adults than the other groups. In fact, the CRP levels increased with the number of times the individuals were bullied.
Young adults who had been both bullies and victims as children had CRP levels similar to those not involved in bullying, while bullies had the lowest CRP - even lower than those uninvolved in bullying. Thus, being a bully and enhancing one's social status through this interaction may protect against increases in the inflammatory marker.
The study has been published online in the Proceedings of the National Academy of Sciences.