It just struck me tonight how horribly Vietnam affected me.

Reevaluating Society's Perception of Shell Shock:
By Annessa Cathleen Stagner West Texas State University

The combination of traditional fighting techniques and new technology in World War I forced both soldiers and officers to face devastating situations that tested not only their courage, but also their mental strength as well. While society had taught men to be tough and brave at all times, many broke upon enduring the horrifying environment of the trenches. It is obvious that men's ability to hold on to such an extreme ideal of manhood was unrealistic; however, many men tried. Jessica Meyers quoted Private Miles, who explained his emotional conflict saying, "I was frightened out of my life at nighttime. I was jellified, but I was more afraid of people knowing that I was afraid-- just a sort of bravado-- I mustn't show them I was afraid." <1> Like private Miles, many men tried to suppress their emotions, stay in control, and live up society's standard of masculinity. The devastating impact of war on soldiers, however, quickly forced society to confront the inability of soldiers to maintain society's idealistic courage. Some returning soldiers suffered through nightmares, while others suffered physically, exhibiting nervous twitches, blindness, or limb dysfunction. <2> In 1915, physician C. S. Myers unknowingly acknowledged the result of soldier's mental conflict between idealistic courage and survival leading to a form of nervous disorder, which he termed shell shock. <3>

While the government did not intend to allow shell shock to hold any legitimacy among its troops, experienced soldiers' and officers' traumatic experiences convinced to advocate for proper treatment of the shell-shocked soldiers. Virtually ignoring the existence of shell shock within common soldiers initially, Peter Leese suggested the government proceeded to improve treatment only as a result of strong public opinion.

The large number of soldiers affected by shell shock continues to engage World War I historians even today. "The heightened code of masculinity that dominated in wartime was intolerable to surprisingly large numbers of men." <4> Nearly 80,000 men in Britain were diagnosed with shell shock during the War, and the number of cases continued to rise after the War ended. Some estimates, including undiagnosed soldiers, claim 800,000 British cases and 15,000 American cases. <5> Shell shock was not just a disease of the common soldier either. Myra Schock acknowledged "historians have generally taken it for granted that officers experienced shell shock in far greater numbers than soldiers of other ranks." <6> Inevitably numerous soldiers from all ranks were diagnosed with shell shock, thus having a tremendous impact on all of society.
http://www.wfa-usa.org/new/shellshock.htm