ual attributes. Their results indicated that, after controlling for the effects of self-reported physical health at war's end and for age, exposure to combat predicted a subject would experience physical decline or death during the postwar interval from 1945 to 1960. Rank and theater of engagement were of little consequence, and self-worth before the war did not moderate the risk of physical decline or death that was associated with combat.

A study of Australian veterans of the Vietnam conflict (O'Toole et al., 1996) found that combat exposure was significantly related to reports of recent and chronic mental disorders, recent hernia and chronic ulcer, recent eczema and chronic rash, deafness, chronic infective and parasitic disease, and chronic back disorders, as well as to symptoms and signs of ill-defined conditions.

Two major contributions to the investigation of war-related illnesses resulted from research into the health problems of Vietnam veterans: (1) the development of case criteria and a label for posttraurnatic stress disorder (PTSD); and (2) a "model" for thinking about the long-term health consequences of a specific exposure (Agent Orange), despite the absence of an acute response. While PTSD was not new, recognition of it and the eventual incorporation of PTSD into both ICD-9 (International Classification of Diseases, 9th revision) and DSM-III (Diagnostic and Statistical Manual of Mental Disorders, 3rd ed.) dates from the Vietnam era. Research on the effects of Agent Orange used in Vietnam also is enriching the understanding of health problems experienced as a result of participation in that conflict.

Other reported health problems are less well-defined and include poorly understood, multisymptom clusters. The literature regarding such reports was summarized by Hyams and colleagues (1996). They found that during the U.S. Civil War, the numerous reported health problems could be separated into two unique illnesses: irritable heart (first identified by J. M. DaCosta) and nostalgia. Irritable heart had no specific sign or pathology and was characterized by shortness of breath, palpitations, chest pain, headache, diarrhea, dizziness, and disturbed sleep. Dr. DaCosta hypothesized that this disease was caused by either an infectious process or strenuous military duties.

The second illness, nostalgia, which is sometimes referred to as an early form of PTSD, most often affected the youngest Civil War soldiers, those 15 and 16 years old. Nostalgia was characterized by excessive thoughts of home, as well as by apathy and loss of appetite. Some of those affected also had diarrhea or chronic fever. AS with irritable heart, there were no characteristic signs. Unlike irritable heart, which was thought to be a physiologic disease, nostalgia was attributed to psychological factors.

During World War I, irritable heart, commonly referred to as effort Syndrome, again became an issue when soldiers reported experiencing the same symptoms, still with no characteristic sign or pathology. The condition was thought to be due to multiple factors, including strenuous military duties, exposure to poison gas, infectious diseases, and psychological distress.

Another illness experienced during World War I was called shell shock, now known as acute combat stress reaction. Its symptoms included a dazed or



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