Diagnostic criteria for 300.6 Depersonalization Disorder 
(cautionary statement)  

A. Persistent or recurrent experiences of feeling detached from, and as if one is an outside observer of, one's mental processes or body (e.g., feeling like one is in a dream). 

B. During the depersonalization experience, reality testing remains intact. 

C. The depersonalization causes clinically significant distress or impairment in social, occupational, or other important areas of functioning. 

D. The depersonalization experience does not occur exclusively during the course of another mental disorder, such as Schizophrenia, Panic Disorder, Acute Stress Disorder, or another Dissociative Disorder, and is not due to the direct physiological effects of a substance (e.g., a drug of abuse, a medication) or a general medical condition (e.g., temporal lobe epilepsy).

Reprinted with permission from the Diagnostic and Statistical Manual of Mental Disorders, fourth Edition. Copyright 1994 American Psychiatric Association