Many people have no doubt read accounts in the general press of the study by Pizarro, Silver and Prause in the Archives of General Psychiatry entitled "Physical and Mental Health Costs of Traumatic War Experience Among Civil War Veterans." You can read the abstract here, although as per my usual gripe the full article is subscription only.
It obviously isn't news that combat is bad for you, even if you don't suffer serious physical injuries. From the author's literature review:
WAR IS PARTICULARLY traumatic for soldiers because it often involves intimate violence, including witnessing death through direct combat, viewing the enemy before or after killing him, and watching friends and comrades die. . . .Many investigators have examined the mental health consequences of exposure to war trauma and found substantial postwar psychiatric difficulties among veterans. Research has also linked war trauma and physical health outcomes, including an increase in negative physical symptom reporting, chronic illness, and death. Traumatic war exposure has also been linked to specific self-reported and objective health problems, such as cardiovascular disease and hypertension and gastrointestinal (GI) disorders.
So what's new in this study? To me, what is most interesting about it is that exposure to greater psychological trauma -- the percentage of a soldier's company killed, in particular -- was associated with physical symptoms, both cardiac and gastrointestinal, but not with so-called "nervous disease" (what we today would call mental disorders) alone, but only for soldiers who were not physically wounded. As a matter of fact, soldiers who were physically injured were less likely to suffer from these symptoms than soldiers who were not, although wounded soldiers were more likely to suffer from nervous diseases.
Back in the 19th Century, the concept of Post Traumatic Stress Disorder had not been developed. Possibly some of these soldiers who were not diagnosed with a "nervous disease" would have gotten that diagnosis today. In any event, what this says to me is that the emotional trauma of war can manifest over the life course in physical symptoms. We don't, obviously, have angiograms EKGs or CT scans or endoscopies of these soldiers. We don't know what physical diagnoses they might receive were a time machine to bring them to us today. But I doubt these symptoms were purely psychogenic. The brain is a physical organ, the nervous system affects the functions of other organs including the secretion of hormones. Psychological damage is a kind of physical damage. This undoubtedly helps to account for some of the unexplained ailments of modern veterans as well.