Being left out or bullied is more likely to lead to depression in children with developmental disabilities than any facet of their condition, new research indicates.

The findings come from a study of 109 kids ages 8 to 17 with various special needs. Researchers asked the children and their parents to fill out questionnaires designed to identify signs of anxiety and depression. Then, the kids were screened to assess whether or not they were bullied or excluded by their peers.

“What is notable about these findings is that despite all the many challenges these children face in relation to their chronic medical or developmental diagnosis, being bullied or excluded by their peers were the factors most likely to predict whether or not they reported symptoms of depression,” said Margaret Ellis McKenna, a senior fellow in developmental-behavioral pediatrics at the Medical University of South Carolina who presented the research Sunday at the Pediatric Academic Societies annual meeting in Boston.

Other factors that McKenna and her colleagues considered included age, gender and the presence of chronic health conditions, but none came close to the influence of the negative peer experiences.

Accordingly, the researchers said that children who report being bullied or excluded should be carefully observed for signs of depression or other internalizing behaviors.

“Professionals need to be particularly alert in screening for the presence of being bullied or ostracized in this already vulnerable group of students,” McKenna said.