Nearly one-third of students at Montreal's Dawson College suffered psychological damage after a gunman opened fire there in 2006, new research reveals.

Nearly 1,000 Dawson College students and college staff took part in the three-year research project in which they were interviewed about the psychological effects of the shooting.

The final report, released Thursday, finds that about 30 per cent of respondents experienced some psychological disorder, such as post-traumatic stress or depression.

People with pre-existing disorders apparently felt the effects for up to 18 months.

"For us, the bottom line is… that rates of depression, rates of substance abuse, rates of anxiety were about double the rate of the general population," Dr. Warren Steiner, one of the researchers, told CTV News Channel on Thursday.

"We've presented a report to the Quebec government that based on our findings, schools need to have integrated disaster response plans, including a psycho-social component, which includes mental health professionals," said Steiner, who serves as psychiatrist-in-chief at the McGill University Health Centre.

"And these plans have to be pre-existing before any event, and have to be far-reaching."

Some 13 per cent of respondents sought professional help for their distress, while another 14 per cent accessed mental health information on the Internet. But close to 70 per cent of those who reported post-crisis symptoms did not seek psychological help.

The authors of the study from the McGill University Health Centre and the Fernand-Seguin research centre of the Louis-H. Lafontaine hospital call the study a world first on the impact of school shootings.

One student, Anastasia DeSousa, was killed and 20 others injured when gunman Kimveer Gill opened fire at the college on Sept. 13, 2006. Gill took his own life after being confronted by police officers.

Robert Soroka was a teacher at the school who witnessed the shootings and eventually participated in the study.

"I can safely say that those moments are still with me, absolutely," he said.

The decision to take part in the research was "painstaking" because, he said, while he felt an obligation to the community, he knew that participating would "reopen old wounds" that he hoped had already healed.

"In fact, that's exactly what happened," he told CTV News Channel. "It's very difficult."

The study authors made several recommendations in their report about providing appropriate psychological support for victims of a similar tragedy.

They recommended creating crisis-management teams to deal with disasters and improving public education on mental illness. The report also recommends better access to psychological help for those affected by a traumatic event.