Although contemporary accounts indicate that stress-induced disorders existed in previous wars, even in the period of the American Civil War, medical and cultural biases were such that no taxonomy for recognizing and diagnosing them was readily available (Marlowe, 2001). It was not until World War I that specific clinical syndromes came to be associated with combat duty; previously, such casualties were assumed to reflect poor discipline or cowardice (Goodwin, 1987). The thinking that dominated diagnostic thought and ways of treating stress-related illnesses in World War I and World War II (and beyond) developed in the late 19th and early 20th centuries and included new categories of diagnoses related to hysteria, hypochondria, and neurasthenia (Marlowe, 2001). The guiding conceptual and theoretical developments emerged from advances in psychiatry and in turn influenced the evolution of the field in civilian society (Pols and Oak, 2007):
The involvement of psychiatrists in military conflicts [during the 20th century] not only resulted in the development of extensive expertise in the management of war-related psychiatric syndromes but also profoundly affected the development of the entire discipline of psychiatry, which incorporated new theoretical perspectives, diagnostic categories, and treatment strategies first proposed and developed by military psychiatrists.
First observed during the Russo-Japanese War (Marlowe, 2001), shell shock—the signature injury of World War I (Jones et al., 2007)—and war neurosis became the popular labels given to acute physical and psychologic symptoms and reactions to combat (Rundell et al., 1989). Shell shock was initially thought to result from brain concussion from nearby shell explosions (for example, from artillery), but the recognition that the symptoms characteristic of shell shock and effort syndrome could also emerge without exposure to explosions suggested psychologic origins (Hyams et al., 1996; Jones et al., 2007; Shephard, 2001; Thakur, 2008). Symptoms of classic war neurosis first described clearly during World War I were similar to those later described by veterans of the Vietnam conflict (Goodwin, 1987). The prolonged chronic symptoms observed in the Vietnam War were later recognized and labeled “postcombat psychiatric disorder” (Sargent and Slater, 1940). Of the 2 million men sent overseas during World War I, about 8% (153,994) were lost to the war effort because of psychologic problems (Strecker, 1944).
The most comprehensive recent review of research evidence on the physiologic, psychologic, and psychosocial effects of deployment and deployment-related stress on health and well-being (IOM, 2008) explicitly included epidemiologic studies of veterans of World War II, the Korean War, and more recent conflicts. The research evidence base on those cohorts is much narrower than that on cohorts of the Vietnam War and more recent conflicts, but evidence of persistent effects, especially with regard to psychologic consequences and PTSD, was observed in those who served in the earlier wars.
During World War II, the psychologic symptoms ascribed to war neurosis were called battle or combat fatigue or exhaustion (Marlowe, 2001; Thakur, 2008). During the early years of that war, psychiatric casualties had increased by some 300% over those in World War I even though the preinduction psychiatric-rejection rate was “three to four times higher” (Figley, 1978). Overall, 1.39 million men suffered some psychiatric symptoms, and 38% (504,000) of