A study has found more than 1,000 Fort McMurray junior and high school students meet the criteria for a mental illness diagnoses as a result of the 2016 wildfires.

As part of a study by a group including researchers from the University of Alberta, Fort McMurray Catholic and public Schools surveyed 70 per cent of its Grade 7-12 students to determine the psychological impact caused by the fires.

Of the 3,070 students surveyed – both in the area or out of town at the time of the wildfire – 46 per cent met criteria for a probable diagnosis of PTSD, anxiety, depression or substance abuse.

The students reportedly experienced low mood, anxiety, difficulty sleeping, difficulty focusing, flashbacks and more, all typical symptoms of PTSD.

"Experiencing that would be very scary," senior researcher Peter Silverstone told CTV News Edmonton. "But having those symptoms 18 months, and even much longer from follow-up studies we're doing is – I think – both surprising and worrying."

The study concluded disasters have a negative impact on youth mental health, and the importance of support for youth after the disaster.