Jeffrey L. Thomas of the Walter Reed Army Institute of Research in Silver Spring, Md., and colleagues analyzed anonymous mental health surveys of 18,305 U.S. Army soldiers -- reserve and non-reserve -- three to 12 months after deployment.
The soldiers were screened for PTSD, depression, alcohol misuse and aggressive behaviors.
"Using the least stringent definition, we observed PTSD rates across Active Component and National Guard study groups, study time points ranging from 20.7 percent to 30.5 percent, and depression rates ranging from 11.5 percent to 16 percent," the study authors said in a statement. "Using the strictest definitions with high symptom rates and serious functional impairment, PTSD prevalence ranged from 5.6 percent to 11.3 percent and depression prevalence from 5 percent to 8.5 percent."
The study, published in the Archives of General Psychiatry, shows that at 12 months after combat, mental health problems among veterans do not abate, and in many cases, increase, Thomas said.
"If soldiers who are struggling with serious functional impairment as the result of a previous deployment are deployed again, there is potential that this could impair their performance in combat," the study said. "This has implications for the safety of unit members and mission success."
2014: The Year in Music [PHOTOS]