HALIFAX - The Canadian military and Veterans Affairs are trying to understand why female personnel in their early 40s, including former and current members, were more than twice as likely to die from suicide as their civilian counterparts.

Groundbreaking research by the two departments and Statistics Canada has shown a statistically higher rate in the number of suicide deaths in female former service personnel between the ages of 40 to 44, compared to their civilian counterparts.

"We're a little bit surprised," Col. Colin MacKay, director of Force Health Protection and co-chair of the study's advisory committee, said in Ottawa.

"This was information we hadn't had before and is very important information...because we can now start to look at it more carefully."

Researchers can't explain the difference for that age group, but MacKay cautions it involves a small number of women over a 35-year period.

There were 37 suicides for women in all age groups who were serving or released from the military, with 29 occurring among females years after they were let go from the forces.

A spokeswoman for Veterans Affairs said in a statement that officials in the department will review their suicide prevention programs in light of the new findings.

"Last year, we undertook a thorough review of suicide prevention activities," the statement said. "Those activities will now be reviewed in light of the high-risk groups identified in the (study)."

Men aged 16 to 44 who had been released from military service also had a higher risk of death from suicide when compared to the same civilian age groups.

They found that people who served from 1972 to 1986 had a greater risk of committing suicide.

Dr. Maureen Carew, an epidemiologist and the study's principal investigator, said they took a closer look at men who were released and went on to commit suicide, finding that many had shorter periods of service and were let go involuntarily.

The suicide rate was two times higher for people with a medical release and one and a half times higher for those who were released involuntarily compared with those who took a voluntary release, the study says.

Dr. Rakesh Jetly, a psychiatrist and adviser to the military on mental health issues, said there may be an elevated rate among people who were released decades before because programs weren't in place to help them transition to the civilian world.

Someone who was forced out of the military for disciplinary or health reasons, for example, was not given advice on finding a job or doctor, or assessed properly for mental health problems, he said.

"In the past, the release process could be very fast and now the process literally takes years," he said. "We're talking about a time when people were less open about mental health issues and less open about seeking care."

He said people who are released now go through case management, are hooked up with Veterans Affairs and get help finding a family physician, job and education.

The report looked at mortality among 188,000 personnel who enrolled between 1972 and 2006 in the regular force. Investigators sifted through the Canadian Mortality Data Base and compared names to the Department of Defence's electronic databases to identify the deceased.

The research also found that women between the age of 20 to 24 had twice the risk of death from unintentional injury compared to their civilian counterparts.

But it's not clear what caused the deaths or if they died while on duty and if there is any link to training or experience.

"Twenty-seven unfortunate deaths in this age group for women, of which probably over half are currently serving members, does warrant further examination by us and we will have a look at this," MacKay said.

Men in the study also had a significantly higher risk of dying in an air and space transport accident compared with males in the general population.

The researchers are also looking at cancer rates for the military and expect to have data from that work by the end of next year. Preliminary numbers indicate the risk from dying from cancer was considerably lower than general public.