MONDAY, Nov. 1 (HealthDay News) -- Military veterans with psychiatric illnesses are at increased risk for suicide, says a new study.

The greatest risk is among males with bipolar disorder and females with substance abuse disorders, according to the researchers at the U.S. Department of Veterans Affairs and Healthcare System and the University of Michigan.

Overall, bipolar disorder (the least common diagnosis at 9 percent) was more strongly associated with suicide than any other psychiatric condition.

The researchers examined the psychiatric records of more than three million veterans who received any type of care at a VA facility in 1999 and were still alive at the beginning of 2000. The patients were tracked for the next seven years.

During that time, 7,684 of the veterans committed suicide. Slightly half of them had at least one psychiatric diagnosis. All of the psychiatric conditions included in the study -- depression, schizophrenia, bipolar disorder, substance abuse disorders, post-traumatic stress syndrome (PTSD) and other anxiety disorders -- were associated with increased risk of suicide.

"In men, the risk of suicide was greatest for those with bipolar disorder, followed by depression, substance abuse disorders, schizophrenia, other anxiety disorders and PTSD," the researchers wrote. "In women, the greatest risk of suicide was found in those with substance abuse disorders, followed by bipolar disorder, schizophrenia, depression, PTSD and other anxiety disorders."

Since bipolar illness was most likely to be associated with suicide, "this makes bipolar disorder particularly appropriate for targeted intervention efforts or attempts to improve medication adherence," the researchers wrote.

The study found that many veterans with psychiatric conditions weren't identified by the VA health system.

"This could be owing to stigma, which may have made individuals less likely to report their mental health symptoms to physicians, an effect that could be more pronounced among men with military experience," the researchers wrote. "These findings highlight the importance of improved identification, diagnosis and treatment of psychiatric diagnoses (particularly bipolar disorder, depression, substance use disorders and schizophrenia) of all health care system users."

The study appears in the November issue of the journal Archives of General Psychiatry.

The U.S. Department of Veterans Affairs has more about veterans' mental health.