Lead author Craig J. Bryan of the University of Utah and associate director of the National Center for Veterans Studies and colleagues surveyed 161 military personnel stationed in Iraq and evaluated for a possible traumatic brain injury.
The study showed the risk for suicidal thoughts or behaviors increased not only in the short term -- 12 months -- but during the individual's lifetime.
The study, published in the Psychiatry, said the risk of suicidal thoughts increased significantly with the number of traumatic brain injuries.
"Up to now, no one has been able to say if multiple traumatic brain injuries, which are common among combat veterans, are associated with higher suicide risk or not," Bryan said in a statement.
Results showed 21.7 percent who had ever sustained more than one traumatic brain injury reported suicidal ideation -- thoughts about or preoccupation with suicide -- at any time in the past. For patients who had received one traumatic brain injury, 6.9 percent reported having suicidal thoughts and 0 percent for those with no traumatic brain injuries.