Suicides among US army personnel rose 80 per cent between 2004 and 2008, finds research by US Army Public Health Command and published online in Injury Prevention.
Around 40% of these suicides might be associated with military events following US involvement in Iraq, say the authors.
The US committed a substantial number of troops to Iraq, starting in 2003, and it continues to be involved in military operations in Afghanistan.
The authors base their findings on trends in US army suicides from 1977 to 2008, using information obtained from the Army Behavioural Health Integrated Data Environment.
This captures data on suicides from several national military sources, and includes clinical consultations, diagnoses, and treatment given.
The analyses showed that suicide rates among soldiers on active duty were in line with expected trends for the 27 years between 1977 and 2003, and had even fallen slightly.
But after 2004 they began to rise, increasing by more than 80% up to 2008, and overtaking comparable rates among the civilian population, which had remained fairly stable during this period.
During 2007 and 2008, 255 soldiers on active duty took their own lives, equivalent to an actual suicide rate of 20 per 100,000 person years, compared with the expected rate of 12 per 100,000 person years.
Analysis of the historical trends, compared with 2008 rates, indicated that 39% of these suicides might be associated with military events following US involvement in Iraq in 2003, say the authors.
Soldiers between the ages of 18 and 24 accounted for almost half (45%) of the suicides; over half (54%) were among soldiers of low rank. Over two thirds (69%) had been deployed in active combat.
The increase in suicides was paralleled by an increase in other mental health issues. Suicide rates were higher among soldiers diagnosed with a mental illness in the preceding year, the data showed.
Outpatient consultations for these disorders nearly doubled from a rate of 116 per 1000 person years in 2003 to 216 per 1000 in 2008. Similarly, admissions to hospital for mental health issues rose from 7.4 per 1000 in 2003 to 14 per 1000 in 2008.
Those who had been admitted to hospital for a mental health disorder were more than 15 times as likely to commit suicide as those who had not been, while those who had had an outpatient consultation for a mental health issue were almost four times as likely to take their own lives.
Depression, anxiety disorders, post-traumatic stress, substance misuse, as well as personality and adjustment disorders and psychosis all conferred a higher suicide risk.
Those with major depression were more than 11 times as likely to commit suicide; those with anxiety disorders were 10 times as likely to do so.
More than one in four of the soldiers who committed suicide had been diagnosed with adjustment disorder, which is a term applied to the immediate emotional fall-out from being in close proximity to stressful events.
These findings highlight the need for better methods of identifying, monitoring, and treating those who are potentially at risk, say the authors.
They go on to say that suicide is complex, with many factors involved, and further research is needed to uncover the specific issues that contributed to the increase between 2004 and 2008.
But they conclude: "This increase, unprecedented in over 30 years of US Army records, suggests that approximately 40% of suicides that occurred in 2008 may be associated with post-2003 events following the major commitment of troops to Iraq, in addition to the ongoing operations in Afghanistan."