A new study examines the phenomenon of “suicide contagion” in teens and recommends that school administrators address the impact of suicide on all students.

Teens who have had a classmate die by suicide—whether they were close friends or not—have an increased risk of contemplating or attempting suicide for up to two years after the event, according to new research published in the Canadian Medical Association Journal.

“We found that exposure to suicide predicts suicidality,” senior author Dr. Ian Colman of the University of Ottawa said in a press release. “This was true for all age groups, although exposure to suicide increased the risk most dramatically in the youngest age group.”

Analyzing data from more than 22,000 children ages 12 to 17 who took part in the National Longitudinal Survey of Children and Youth, researchers found that a schoolmate’s suicide had the most profound impact on younger students.

Researchers learned that students ages 12 and 13 were five times more likely to have suicidal thoughts if a schoolmate committed suicide. Students ages 14 and 15 were three times more likely to think of their own suicide, while students ages 16 and 17 were twice as likely.

In the U.S., suicide is the third leading cause of death for teens after accidents and homicide. In this Canadian study, 24 percent of the teens surveyed had had a schoolmate commit suicide, and 20 percent personally knew someone who had died by his or her own hand.

“The idea that suicide is contagious has always been controversial for various reasons; however, this important study should put many, if not all, doubts to rest,” India Bohanna, a mental health research fellow at James Cook University in Australia, wrote in a commentary on the research. “A unified and concerted effort now needs to be directed toward developing evidence-based postvention strategies. We need to know what works in mitigating the risk of contagion and why.”

Students exposed to cyberbullying are three times more likely to attempt suicide than those who have not been bullied, according to new research unveiled at the American Psychiatric Association’s annual meeting this week in San Francisco.

However, students who experience typical schoolyard bullying are only twice as likely to commit suicide as students who experience no bullying at all.

Lead researcher Dr. Kristi Kindrick of the University of Arkansas drew on data from the U.S. Centers for Disease Control’s 2011 Youth Risk Behavior Surveillance. She began her research after a Little Rock, Ark., teen committed suicide after being bullied.

“What’s interesting is girls are twice as likely to engage in cyberbullying as men,” Kindrick said. “It appears the movie ‘Mean Girls’ has some truth to it.”