Depersonalization (or depersonalisation) is an anomaly of self-awareness. It consists of a feeling of watching oneself act, while having no control over a situation. Subjects feel they have changed, and the world has become vague, dreamlike, less real, or lacking in significance. It can be a disturbing experience, since many feel that, indeed, they are living in a "dream". Chronic depersonalization refers to depersonalization disorder, which is classified by the DSM-IV as a dissociative disorder. Though degrees of depersonalization and derealization can happen to anyone who is subject to temporary anxiety/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, borderline personality disorder, obsessive-compulsive disorder, migraine and sleep deprivation. It can be considered desirable, such as in the use of recreational drugs.
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".
Individuals who experience depersonalization feel divorced from their own personal physicality by sensing their body sensations, feelings, emotions and behaviors as not belonging to the same person or identity. Often a person who has experienced depersonalization claims that things seem unreal or hazy. Also, a recognition of self breaks down (hence the name). Depersonalization can result in very high anxiety levels, which further increase these perceptions. Individuals with depersonalization often find it hard to remember anything they saw or experienced while in third person.
Depersonalization is a subjective experience of unreality in one's sense of self, while derealization is unreality of the outside world. Although most authors currently regard depersonalization (self) and derealization (surroundings) as independent constructs, many do not want to separate derealization from depersonalization.
Depersonalization is the third most common psychological symptom, after feelings of anxiety and feelings of depression. Depersonalization is a symptom of anxiety disorders, such as panic disorder. It can also accompany sleep deprivation (often occurring when suffering from jet lag), migraine, epilepsy (especially temporal lobe epilepsy), obsessive-compulsive disorder, stress, and anxiety. Interoceptive exposure is a non-pharmacological method that can be used to induce depersonalization. A similar and overlapping concept called ipseity disturbance may be part of the core process of schizophrenia spectrum disorders. However, specific to the schizophrenia spectrum seems to be "a dislocation of first-person perspective such that self and other or self and world may seem to be non-distinguishable, or in which the individual self or field of consciousness takes on an inordinate significance in relation to the objective or intersubjective world" (emphasis in original).
A study of undergraduate students found that individuals high on the depersonalization/derealization subscale of the Dissociative Experiences Scale exhibited a more pronounced cortisol response. Individuals high on the absorption subscale, which measures a subject's experiences of concentration to the exclusion of awareness of other events, showed weaker cortisol responses.
Pharmacological and situational causes 
Depersonalization has been described by some as a desirable state, particularly by those that have experienced it under the influence of mood-altering recreational drugs. It is an effect of dissociatives and psychedelics, as well as possible side effect of caffeine, alcohol, cannabis, and minocycline. It is a classic withdrawal symptom from many drugs.
Benzodiazepine dependence, which can occur with long term use of benzodiazepines, can induce chronic depersonalization symptomatology and perceptual disturbances in some people, even in those who are taking a stable daily dosage, and it can also become a protracted feature of the benzodiazepine withdrawal syndrome.
Lieutenant Colonel Dave Grossman, in his book On Killing, suggests that military training artificially creates depersonalization in soldiers, suppressing empathy and making it easier for them to kill other human beings.
Treatment is dependent on the underlying cause, whether it is organic or psychological in origin. If depersonalization is a symptom of neurological disease, then diagnosis and treatment of the specific disease is the first approach. Depersonalization can be a cognitive symptom of such diseases as amyotrophic lateral sclerosis, Alzheimer's, multiple sclerosis (MS), neuroborreliosis (Lyme disease), or any other neurological disease affecting the brain. For those suffering from depersonalization with migraine, tricyclic antidepressants are often prescribed.
If depersonalization is a symptom of psychological causes such as developmental trauma, treatment depends on the diagnosis. In case of dissociative identity disorder or DD-NOS as a developmental disorder, in which extreme developmental trauma interferes with formation of a single cohesive identity, treatment requires proper psychotherapy, and—in the case of additional (co-morbid) disorders such as eating disorders—team of specialists treating such an individual. It can also be a symptom of borderline personality disorder, which can be treated in the long term with proper psychotherapy and psychopharmacology.
The treatment of chronic depersonalization is considered in depersonalization disorder.
A recently-completed study at Columbia University in New York City has shown positive effects from transcranial magnetic stimulation (TMS) to treat depersonalization disorder. Currently, however, the FDA has not approved TMS to treat DP.
A recent Russian study showed that naloxone, a drug used to reverse the intoxicating effects of opioid drugs, can successfully treat depersonalization disorder. According to the study: "In three of 14 patients, depersonalization symptoms disappeared entirely and seven patients showed a marked improvement. The therapeutic effect of naloxone provides evidence for the role of the endogenous opioid system in the pathogenesis of depersonalization."
The Depersonalisation Research Unit at the Institute of Psychiatry in London is a world leader in research in depersonalization disorder. Researchers there use the acronym DPAFU (Depersonalisation and Feelings of Unreality) as a shortened label for the disorder.
See also 
- Brain fog
- Catatonic state
- Compassion fatigue
- Dissociation (psychology)
- Ego death
- Hallucinogen persisting perception disorder
- Human spirit
- Nina Searl
- Out-of-body experience
- Post-traumatic stress disorder
- Psychedelic experience
- Psychological trauma
- Spiritual crisis
- Falling (sensation)
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