Teens who used cannabis in the past year were far more likely to develop psychotic disorders, a new study from the University of Toronto found. Users faced an 11 times higher risk—jumping to 27 times higher for those ending up in hospitals or ERs.

Dr. Leslie Hulvershorn, a child psychiatrist not involved in the study, said it’s common to see heavy cannabis use in teens with psychotic symptoms. “It’s rare to see a young person with psychosis who hasn’t used cannabis,” she noted.