The emotional impact of injury deepens in the first year after evacuation from combat according to a study by Thomas A. Grieger, M.D., and colleagues of the Uniformed Services University of the Health Sciences (USU), Walter Reed Army Medical Center, and Walter Reed Army Institute of Research.

The study, which is the first report to focus on U.S. soldiers seriously wounded or injured during combat in Iraq or Afghanistan, demonstrates the importance of self-reported physical problems as a sign of psychiatric disorders. The study also found that a soldiers' personal rating of their own physical problems in contrast to that of medical personnel were more significantly associated with posttraumatic stress disorder (PTSD) later.

The presence of PTSD or depression seven months after a soldier was seriously injured was associated with the severity of the physical problem one month after the actual injury. These findings came from the screening of more than 600 soldiers, who were the most severely wounded of those receiving combat injuries from March 2003 to September 2004. Of those soldiers, 243 completed assessments at the one, four, and seven month time frame after being injured. The rates of PTSD and depression was 4 percent at one month, 12 percent at four months, and 19 percent at seven months.

The findings will be reported in the October 2006 issue of The American Journal of Psychiatry, the official journal of the American Psychiatric Association titled, “Posttraumatic Stress Disorder and Depression in Battle-Injured Soldiers.�

Established by the U.S. Congress in 1972, the Uniformed Services University of the Health Sciences (http://www.usuhs.mil) is located on the campus of the National Naval Medical Center in Bethesda, Md., and is the nation's only federal school of medicine, including a graduate program in the biomedical sciences and graduate school of nursing.

Source: Medical News Today

I think this varies...if we consider one isolated incident this is fine. But often there are a combination of factors that either build up over time, or occur within a short time frame leading to some symptoms until there is one or more things happen which set things off.
Perhaps in that case it is easier to come back down to 'reality' as the combination of things are dealt with one by one, until time comes to move on again. I do think that we can do that, although some sensitivities remain with regard to being sent back down again.