Posttraumatic stress disorder (PTSD) was associated in the past mainly with combatrelated events. This was reflected in the names given to the disorder, ie, “shell shock,” “soldier's heart,” “combat neurosis,” and “operational fatigue.” Only following the realization that PTSD can be related to all types of traumatic events, including noncombat associated events, were the terms “traumatic neurosis” and, later, “PTSD” coined. These new terms reflect the understanding that the condition need not necessarily be associated with war, but may also be related to events such as a severe automobile accident, violent personal assault (eg, rape, physical attack, robbery, or mugging), terrorist attack, natural or human-made disaster (such as a fire), witnessing serious injury or death due to any of the above, as well as to other situations, such as being kidnapped or being held hostage.

The tendency to interpret the symptoms of what we would consider now as PTSD, as a “normal response” to traumatic events was another factor that held up progress in the field. It is important to note that PTSD is a pathological response: The vast majority of individuals who are exposed to a traumatic event will later adapt and continue on with their lives. Only a small percent, which partially depends on the type of trauma and is partially associated with several risk factors, will develop a pathological fixation on the traumatic event, namely, PTSD.

It has been estimated that approximately one-third of the population will be exposed to a severe trauma (according to the definition of PTSD) during their lifetime.

This article reviews a series of studies conducted on Israeli war veterans that assessed the interrelationship of posttraumatic stress disorder (PTSD) and comorbid disorder, focusing on five issues in particular: (1) the frequency of comorbidity among veterans diagnosed with PTSD; (2) how this comorbidity can be accounted for; (3) whether PTSDs with and without comorbidity are different; (4) the validity of PTSD as a distinct diagnosis; and (5) the clinical implications of comorbidity of PTSD.