We hear a lot nowadays about PTSD in members of the military who served in Iraq and Afghanistan. I've even learned a little bit about how little support Vietnam veterans got. What happened to WWII vets after the war? Such a large part of the population was involved, but you never hear about people who weren't able to transition back.
It's important to establish something first. PTSD is a modern term. In the past, similar psychological issues were referred to as shell shock (when it was believed that the overpressure wave generated by high explosives disrupted the brain and was the cause of the symptoms), combat fatigue, Guadalcanal Neurosis, among other names.
Many were simply discharged from service as Psychiatric casualties and sent back without any additional care. Particularly bad cases usually ended up in military hospitals for long term care.
Part of my undergraduate thesis deals with issues of psychiatric illness (what we would now likely term as PTSD) in the Pacific Theater of Operations. Here's some relevant sections:
In addition to near catastrophic malaria rates early on in the Pacific, American forces also encountered another epidemic: psychiatric disability. As noted earlier, the conditions in the Pacific were sufficient to considerably exacerbate the ever present threat of psychiatric casualties presented by war, commonly lumped together into catch all terms such as “shell shock” (prevalent during World War I) and “combat fatigue,” or “Guadalcanal Neurosis.” Combat fatigue became the new catch-all term in World War II after it was discovered that the psychiatric issues encountered were not a direct result of the concussive effects of high explosive shelling. “Guadalcanal Neurosis” was an early diagnosis for combat fatigue after it reached near epidemic rates on Guadalcanal.^1 Josephine Bresnehan notes that within six months of the outbreak of the fighting, “the difference between soldiers expectations and their experiences had generated more physical and psychological distress than their training taught them to handle and thus began to precipitate a morale meltdown in the Pacific theater.”^2 The psychiatric crisis in the Pacific only got worse: by October of 1943, more than 10,000 men were being discharged per month due to what was being labeled as psychiatric disabilities.^3 In some areas, these psychiatric casualties made up more than half of all casualties,^4 with the balance of the casualties being made up of men stricken by disease, and those wounded by enemy fire.
Another section regarding the development of in theater treatment for psychiatric in the late stages of the war:
Psychiatric casualties saw similar reductions as new treatment techniques emerged. Prior to World War II, psychiatrists had thought that they had solved the mystery of shell shock: it was not, in fact, the result of the repeated concussive forces of artillery bombardments, but was rather childhood trauma being manifested as a psychiatric illness when the affected soldier was exposed to traumatic battlefield conditions.^1 As a result, soldiers were subjected to induction psychiatric screenings, as it would be impossible to “set off this disorder in anyone who was not already psychologically predisposed.”^2 However, as rates of “war neurosis” and “combat fatigue” spiralled out of control in the early stages of the war in the Pacific, doctors began taking a very different approach. Morale programs were enacted to attempt to keep the spirits of the soldiers up, and troops were rotated off the front line with greater frequency. If soldiers showed signs of being on the verge of breaking down, rather than keeping them in the fight until a breakdown actually occurred, they would be pulled off the line for a minimum of 48 hours of “rapid return” therapy to determine if they were fit to return to duty after a small break from the horrors of combat, or if they needed a longer recuperation period.^3
Bresnahan, Josephine C. Dangers in Paradise: The Battle Against Combat Fatigue in the Pacific War. Ph.D. dissertation, Harvard University, 1999. Ann Arbor, MI: UMI, 2000.
Sledge, Eugene B. With the Old Breed: At Peleliu and Okinawa. New York: Oxford University Press, 1992.
Long story short: this sort of medical issue was not very well understood at the time. I don't have any training in psychology/psychiatry, so I can't really give much on the medical side. Because it was poorly understood, treatment was initially underdeveloped, and matured throughout the war. The issues that we now term PTSD were not formally classified in the DSM until the 4th revision of the DSM in 1980. Because of this, not a whole lot of study was put into treatment of what is now PTSD, simply because it wasn't a recognized issue.
In the last episode of HBO's The Pacific, the wives of one of the veterans talks about how for years after the war, he had to sleep in a separate bedroom from her at night because of his night terrors from his experiences in the war. I believe she recognizes that this was likely untreated PTSD. Veterans mostly had to deal with these issues themselves. If the manifestation of symptoms was truly debilitating, then they would likely be entered into long term treatment, but for most of them, they were discharged during or after the war and more or less put out on their own. There was rudimentary treatment during the war, but the aim of the treatment was to either rehabilitate the soldiers so they could continue fighting, or determine that they were lost causes and medically discharge them.