Depersonalization can consist of a detachment within the self, regarding one's mind or body, or being a detached observer of oneself. Subjects feel they have changed and that the world has become vague, dreamlike, less real, lacking in significance or being outside reality while looking in. It can be a disturbing experience. Chronic depersonalization refers to depersonalization-derealization disorder, which is classified by the DSM-5 as a dissociative disorder.
Though degrees of depersonalization and derealization can happen to anyone who is subject to temporary anxiety or stress, chronic depersonalization is more related to individuals who have experienced a severe trauma or prolonged stress/anxiety. Depersonalization-derealization is the single most important symptom in the spectrum of dissociative disorders, including dissociative identity disorder and "dissociative disorder not otherwise specified" (DD-NOS). It is also a prominent symptom in some other non-dissociative disorders, such as anxiety disorders, clinical depression, bipolar disorder, schizophrenia, schizoid personality disorder, hypothyroidism or endocrine disorders, schizotypal personality disorder, borderline personality disorder, obsessive-compulsive disorder, migraines, and sleep deprivation; it can also be a symptom of some types of neurological seizure.
In social psychology, and in particular self-categorization theory, the term depersonalization has a different meaning and refers to "the stereotypical perception of the self as an example of some defining social category".