A psychological disorder is difficult to define. There is no consensus on the definition of a psychological disorder. A psychological disorder definition should include the following four characteristics:

1. Personal distress
   The disorder must result in personal distress.
2. Disability
   The disorder must result in an impairment in some important area of life.
3. Violation

A correct diagnosis will allow the clinician to describe base rates, causes and treatment. Reliability and validity are the cornerstones of any diagnostic or assessment procedure. Reliability refers to the consistency of measurement. Validity refers to measuring what you want to measure. Alternate form reliability refers to the extent to which scores on two forms of the test

Anxiety disorders include fear and anxiety. Anxiety refers to apprehension over an anticipated problem. Fear is a reaction to immediate danger. Fear happens at the moment and anxiety involves a future threat. In all anxiety disorders, except for a panic disorder, the symptoms must persist for at least 6 months. The symptoms must persist for at least one

Dissociation refers to some aspect of emotion, memory or experience being inaccessible consciously. Depersonalization/derealization involves a form of dissociation involving detachment. The person feels removed from the sense of self and surroundings. The lifetime prevalence of depersonalization/derealization disorder is about 2.5%. The lifetime prevalence of dissociative amnesia is about 7.5%. The lifetime prevalence of dissociative identity disorder is