School can be a dangerous place when bullies stalk the playground. The damage bullies inflict may go far beyond scrapes and soon-dried tears, according to a study by Dr. Andrea Schreier published this month in the Archives of General Psychiatry.

Dr. Schreier monitored 6.437 children from the ages of 7 to 12. Every year the children were given thorough physical and psychological assessments, and this data was combined with parental surveys to determine if there was a correlation between bullying and psychosis. Psychotic symptoms (like hallucinations and delusions) were twice as likely for children who had been bullied, even adjusting for other psychiatric illnesses as well as family situation and intelligence.

The doubling of risk is strong evidence of a correlation on its own, and it appears even more legitimate when viewed along with the more precise finding that the risk of psychosis tracks with the severity and regularity of bullying. There is, however, the possibility that bullying occurs because of a mental abnormality rather than the other way around. It seems less likely that latent psychosis would make children a target, but the possibility at least merits investigation.

These results call on parents and school administrators to step up their efforts to prevent bullying. Aggression that causes psychosis cannot be let go as simply “kids being kids”.