About a quarter of those who killed themselves had a history of at least one psychiatric disorder. Of those, about 20 percent had been diagnosed with a mood disorder such as bipolar disorder and/or depression; and 8 percent had been diagnosed with an anxiety disorder, including post traumatic stress disorder - one of the signature injuries of the conflict in Iraq.
Firearms were the most common method of suicide. Those who attempted suicide but didn't succeed tended more often to take overdoses and cut themselves.
In a service of more than a half million troop, the 99 suicides amounted to a rate of 17.3 per 100,000 - the highest in the past 26 years, the report said. The average rate over those years has been 12.3 per 100,000.
The rate for those serving in the wars stayed about the same, 19.4 per 100,000 in 2006, compared with 19.9 in 2005.
The US Army said the information was compiled from reports collected as part of its suicide prevention program - reports required for all "suicide-related behaviors that result in death, hospitalization or evacuation" of the soldier. It can take considerable time to investigate a suicide and, in fact, the Army said that in addition to the 99 confirmed suicides last year, there are two other deaths suspected as suicides in which investigations were pending.
