Young adults who were bullied when they were kids may have higher levels of inflammation, compared with young adults who bullied others in childhood, a new study suggests.
In the study, the researchers measured the participants' levels of C-reactive protein (CRP), one marker of inflammation. People's levels of this protein increase in response to inflammation, which is a risk factor for health problems such as heart disease.
The researchers found that the people who had experienced bullying as kids had higher CRP levels on average, compared with the people who had either been bullies, or so-called bully-victims —who had been both bullies and bullying victims.
Moreover, the more bullying people had experienced as children, the more their CRP levels increased, the researchers found.
"CRP levels are affected by a variety of stressors, including poor nutrition, lack of sleep and infection, but we've found that they are also related to psychosocial factors," William E. Copeland, an associate professor of psychiatry and behavioral sciences at Duke University School of Medicine, said in a statement.
Previous research has shown that childhood bullying victims may experience social and emotional problems as adults. However, bullied kids also tend to experience physical problems, such as pain, and report getting sick more often than kids who are not bullied, so the exact link is not clear, according to the researchers. [9 Weird Ways Kids Can Get Hurt]
In the study, the researchers examined health and bullying data from 1,420 peoplecollected over more than 20 years. The researchers measured the participants' CRP levels when the participants were between ages 9 and 16, and again when they were 19 to 21 years old.
Although CRP levels increased in all participants as they reached the 19-21 age range, those who had been bullied had higher levels than the other groups, the researchers found.
The researchers also found that compared with people who had not been involved in bullying at all, those who had been bullies had lower levels of CRP, and the former bully-victims had similar levels of CRP.
"Our study found that a child's role in bullying can serve as either a risk or a protective factor for low-grade inflammation," Copeland said.
Because the former bullies had the lowest CRP levels among all study participants, the results may indicate that somehow, bullying other kids may protect the bullies against future increases in the inflammatory marker, the researchers speculated.
Reducing the rates of bullying and bullying-related inflammation could help lower the risk of diseases that are related to inflammation, the researchers said.
The study was published online Monday (May 12) in the journal Proceedings of the National Academy of Sciences (PNAS).