Researchers at Yale School of Medicine have found signs of an apparent connection between bullying, being bullied and suicide in children, according to a new review of studies from 13 countries.

"While there is no definitive evidence that bullying makes kids more likely to kill themselves, now that we see there's a likely association, we can act on it and try to prevent it," said review lead author Young-Shin Kim, M.D., assistant professor at Yale School of Medicine's Child Study Center.

In the review, Kim and colleague Bennett Leventhal, M.D., analyzed 37 studies that examined bullying and suicide among children and adolescents. The studies took place in the United States, Canada, several European countries (including the United Kingdom and Germany), South Korea, Japan and South Africa.

Almost all of the studies found connections between being bullied and suicidal thoughts among children. Five reported that bullying victims were two to nine times more likely to report suicidal thoughts than other children were.

Not just the victims were in danger: "The perpetrators who are the bullies also have an increased risk for suicidal behaviors," Kim said.

However, the way the studies were designed made it impossible for researchers to determine conclusively whether bullying leads to suicide, Kim said. In addition, the authors report that most of the studies failed to take into account the influence of factors like gender, psychiatric problems and a history of suicide attempts.

Kim said her interest in bullying grew several years ago when she visited South Korea and heard several new slang terms referring to bullies and their victims. The words reflected "an elaborated system of bullying," she said.

According to international studies, bullying is common and affects anywhere from 9 percent to 54 percent of children. In the United States, many have blamed bullying for spurring acts of violence, including the Columbine High School massacre.

In the United States, many adults scoff at bullying and say, "Oh, that's what happens when kids are growing up," according to Kim, who argues that bullying is serious and causes major problems for children.

Kim is currently studying whether being bullied actually leads to suicide, although she acknowledges it will be difficult for researchers to get a firm grasp on a cause-and-effect relationship. She said that to confirm a definitive link, researchers would have to rule out the possibility that some unknown factor makes certain children more susceptible to both bullying and suicide.

For now, Kim said, the existing research should encourage adults to pay more attention to bullying and signs of suicidal behavior in children. "When we see kids who are targets of bullying, we should ask them if they're thinking about hurting themselves," she said. "We should evaluate and prevent these things from happening."

Citation: Int J Adolesc Med Health 20 (2), 2008.