Veterans are as much as two times more likely than others to commit suicide, studies have shown.

A University of Michigan researcher recently explored why.

U-M psychiatry professor Mark Ilgen wanted to know which vets in particular were at an elevated risk of suicide.

Ilgen, who also works with the Ann Arbor VA, studied suicide risk among more than 3 million veterans who received care at a Veterans Affairs Healthcare Facility in 1999. Seven years later, 7,684 of those veterans had committed suicide.

Just under half of those who took their lives had at least one psychiatric diagnosis.

But the least common diagnosis, bipolar disorder, had a stronger association with suicide than any other condition. Other conditions include depression, substance abuse disorders, schizophrenia, post-traumatic stress disorder and other anxiety disorders, his research showed. Bipolar disorder had been diagnosed in 9 percent of those who committed suicide.

Why is that association important?

Now that those with bipolar disorder have been identified as having a greater risk for committing suicide, Ilgen hopes his work will improve suicide prevention efforts and help doctors assist bipolar vets in particular to keep taking their medications.

The VA constitutes the largest single health care system in the country. Current numbers show 5,535,315 individuals are using a VA hospital for care.

The research is published in the November issue of Archives of General Psychiatry and supported by the VA Office of Mental Health Services and other federal sources.

Juliana Keeping is a health and environment reporter for AnnArbor.com. Reach her at julianakeeping@annarbor.com or 734-623-2528. Follow Juliana Keeping on Twitter