An alternative classification system, the World Health Organization's International Classification of Diseases, or ICD-10, uses a comparable but somewhat different symptom summary . It is when many symptoms persist for weeks or months, or when they are extreme, that professional help may be indicated. Postponing needed intervention for a year or more, and allowing avoidance defenses to develop, could make the work much more difficult. Depression, Anxiety, and Dissociation are three other disorders that may sometimes arise after traumatic experiences, but Somatoform disorders are also seen in some populations. The differences may result from how the particular individual deals with or expresses their stress, and probably depend some on the individual's subjective interpretation of the stress as well.
Individual differences affect both the severity and the type of symptoms experienced.
For example, almost everyone dissociates to some degree. Dissociation is a fairly normal coping strategy in the face of overwhelming stress, but extreme dissociative tendencies may be pathological. Neils Waller and colleagues identified a separate 'taxon' of pathological dissociation that appears clinically useful in screening for suspected dissociative disorders, calculated from a subset of items in the DES, or Dissociative Experiences Scale. Thankfully, Darryl Perry has translated this into a downloadable MS-Excel 97 spreadsheet , described more fully at the ISSD website. PTSD is officially classed as an anxiety disorder, but some have argued that it fits more closely with the dissociative disorders, and others feel it belongs by itself.