such as proximity, immediacy, and expectancy (PIE), this new diagnosis was taken seriously and recovery was made the first priority. Prevalence Post-traumatic stress disorder has always been prevalent whether it was recognized as a psychological disorder or not. Yet, because PTSD was not recognized as an official disorder, it is difficult to estimate what the prevalence rate during WWII was. A rough estimate, found through hospitalization records, suggests that approximately 43 per 1000 soldiers were hospitalized due to war traumas. Again, however, this estimate is only based upon those who actually sought help, with many at this time not seeking help. Another prevalence rate, found in the 1950s, suggests that about 10% of WWII soldiers had PTSD at some point. While it is difficult to retroactively discern prevalence for PTSD in WWII soldiers, what is clear is that it is prevalent now more than ever due to the long-lasting effects of combat in World War II. For example, half of all male veterans 65 and older have had military experience, which predisposes them to the acquisition of PTSD. Thus, PTSD continues to affect World War II veterans and their families. Symptoms Symptoms of post-traumatic stress disorder differ from person to person in that they can begin shortly after a traumatic event or even years after the event. Moreover, symptoms can continue to present long after the traumatic event's occurrence, with some people experiencing symptoms for the rest of their lives. Symptoms of PTSD can be grouped into four main categories: "Intrusive memories, avoidance, negative changes in thinking and mood, and changes in physical and emotional reactions". Intrusive memories can include symptoms such as nightmares, flashbacks, recurring memories of the event, and emotional and physical stress upon encountering things that remind them of their trauma. Symptoms for avoidance behavior include avoiding thoughts and conversations surrounding the event, as well as people, places, or other things that remind them of what happened. This, understandably, occurs due to intrusive memories that persistently take place, which makes PTSD patients want to avoid these feelings. Negative changes in thinking and mood can force patients into experiencing memory loss (especially in regard to the traumatic event), hopelessness about themselves and their future, difficulty maintaining relationships, and a struggle in experiencing positive emotions. Changes in physical and emotional reactions are seen through behaviors such as trouble sleeping, difficulty concentrating, always being on guard, and becoming startled easily.