To diagnose post-traumatic stress disorder in a patient, a psychologist will use a rating scale, such as the Clinician-Administered PTSD Scale (CAPS). Seventeen criteria are used in diagnosis, where the patient is rated on frequency and intensity. This is done by asking the patient how often the symptom occurred in the past week, and how much distress it caused. Patients may not experience all of the criteria, but can still be diagnosed with post-traumatic stress disorder. The symptoms must have started after the trauma for the post-traumatic disorder diagnosis criteria. Therefore, if a person was already hypervigilant before an event and it is not due to the trauma, it is not considered a positive criterion for diagnosis.
The first criterion for a post-traumatic stress disorder diagnosis is experiencing unwanted memories of the event without being exposed to reminders. In addition, the psychologist will ask if these unwanted memories occur during waking hours or only in dreams.
If unwanted memories occur after exposure to a reminder, it is considered to be the second criterion for diagnosis.
Reliving the Event
Patients may feel that they are reliving the event, which can cause severe distress.
Some post-traumatic stress disorder patients may have unpleasant dreams after the event.
Avoid Thinking About the Event
Besides trying not to think about the traumatic event, the patient may also try to avoid feelings associated with that event, like rage, sadness or guilt.
Staying Away From Reminders
Staying away from reminders of the traumatic event, like people, activities and situations, is another criterion.
Inability to Recall
Another criterion for post-traumatic stress disorder is the inability to recall details about the traumatic event (psychogenic amnesia).