Depersonalization is a dissociative phenomenon characterized by a subjective feeling of detachment from oneself, manifesting as a sense of disconnection from one's thoughts, emotions, sensations, or actions, and often accompanied by a feeling of observing oneself from an external perspective.^[1][2] Subjects perceive that the world has become vague, dreamlike, surreal, or strange, leading to a diminished sense of individuality or identity. Sufferers often feel as though they are observing the world from a distance,^[3] as if separated by a barrier "behind glass".^[2] They maintain insight into the subjective nature of their experience, recognizing that it pertains to their own perception rather than altering objective reality. This distinction between subjective experience and objective reality distinguishes depersonalization from delusions, where individuals firmly believe in false perceptions as genuine truths. Depersonalization is also distinct from derealization, which involves a sense of detachment from the external world rather than from oneself.

Depersonalization/derealization disorder refers to chronic depersonalization, classified as a dissociative disorder^[4] in both the DSM-4 and the DSM-5, which underscores its association with disruptions in consciousness, memory, identity, or perception.^[5] This classification is based on the findings that depersonalization and derealization are prevalent in other dissociative disorders including dissociative identity disorder.^[6]

Though degrees of depersonalization 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,^[7] schizoid personality disorder, hypothyroidism or endocrine disorders,^[8] 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, and it has been suggested that there could be common aetiology between depersonalization symptoms and panic disorder, on the basis of their high co-occurrence rates.^[2]

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".^[9]

Individuals who experience depersonalization feel divorced from their own personal self by sensing their body sensations, feelings, emotions, behaviors, etc. as not belonging to the same person or identity.^[10] Often a person who has experienced depersonalization claims that things seem unreal or hazy. Also, a recognition of a self breaks down (hence the name). Depersonalization can result in very high anxiety levels, which further increase these perceptions.^[11]

Depersonalization is a subjective experience of unreality in one's self, while derealization is unreality of the outside world. Although most authors currently regard depersonalization (personal/self) and derealization (reality/surroundings) as independent constructs, many do not want to separate derealization from depersonalization.^[12]

Despite the distressing nature of symptoms, estimating the prevalence rates of depersonalization is challenging due to inconsistent definitions and variable timeframes.^[2]

Depersonalization is a symptom of anxiety disorders, such as panic disorder.^[13][14] It can also accompany sleep deprivation (often occurring when experiencing jet lag), migraine, epilepsy (especially temporal lobe epilepsy,^[15] complex-partial seizure, both as part of the aura and during the seizure^[16]), obsessive-compulsive disorder, severe stress or trauma, anxiety, the use of recreational drugs^[17] —especially cannabis, hallucinogens, ketamine, and MDMA, certain types of meditation, deep hypnosis, extended mirror or crystal gazing, sensory deprivation, and mild-to-moderate head injury with little or full loss of consciousness (less likely if unconscious for more than 30 minutes). Interoceptive exposure is a non-pharmacological method that can be used to induce depersonalization.^[18][8]

In the general population, transient depersonalization and derealization are common, having a lifetime prevalence between 26 and 74%.^[2] A random community-based survey of 1,000 adults in the US rural south found a 1-year depersonalization prevalence rate at 19%. Standardized diagnostic interviews have reported prevalence rates of 1.2% to 1.7% over one month in UK samples, and a rate of 2.4% in a single-point Canadian sample.^[2] In clinical populations, prevalence rates range from 1% to 16%, with varying rates in specific psychiatric disorders such as panic disorder and unipolar depression.^[2] Co-occurrence between depersonalization/derealization and panic disorder is common, suggesting a possible common etiology. Co-morbidity with other disorders does not influence symptom severity consistently.^[14]

Depersonalization occurs 2-4 times more in women than in men,^[19] but depersonalization/derealization disorder is diagnosed approximately equally across men and women, with symptoms typically emerging around the age of 16.^[14]

A similar and overlapping concept called ipseity disturbance (ipse is Latin for "self" or "itself"^[20]) 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).^[7]

For the purposes of evaluation and measurement depersonalization can be conceived of as a construct and scales are now available to map its dimensions in time and space.^{[clarification needed][21]} 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 in stress. 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.^[22]

Depersonalization can arise from a variety of factors, of both a psychological and physiological nature. Common immediate precipitants include instances of severe stress, depressive episodes, panic attacks, and the consumption of psychoactive substances such as marijuana and hallucinogens. Additionally, there exists a correlation between frequent depersonalization and childhood interpersonal trauma, particularly cases involving emotional maltreatment.^[14]

A case-control study conducted at a specialized depersonalization clinic included 164 individuals with chronic depersonalization symptoms, of which 40 linked their symptoms to illicit drug use. Phenomenological similarity between drug-induced and non-drug groups was observed, and comparison with matched controls further supported the lack of distinction. The severity of clinical depersonalization symptoms remains consistent regardless of whether they are triggered by illicit drugs or psychological factors.^[23]

Currently, no universally accepted treatment guidelines have been established for depersonalization. Pharmacotherapy remains a primary avenue of treatment, with medications such as clomipramine, fluoxetine, lamotrigine, and opioid antagonists being commonly prescribed. However, it is important to note that none of these medications have demonstrated a potent anti-dissociative effect in managing symptoms.^[14]

In addition to pharmacological interventions, various psychotherapeutic techniques have been employed in attempts to alleviate depersonalization symptoms. Modalities such as trauma-focused therapy and cognitive-behavioral techniques have been utilized, although their efficacy remains uncertain and not firmly established.^[14]

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 disease, multiple sclerosis (MS), or any other neurological disease affecting the brain.^{[citation needed]} For those with both depersonalization and 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—a 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.^[38]

The treatment of chronic depersonalization is considered in depersonalization disorder.

A 2001 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."^[39] The anticonvulsant drug lamotrigine has shown some success in treating symptoms of depersonalization, often in combination with a selective serotonin reuptake inhibitor and is the first drug of choice at the depersonalisation research unit at King's College London.^[38][40][41]

Interest in DPDR has increased over the past few decades, leading to a large accumulation of literature on dissociative disorders. There has been a shift towards the use of research studies, rather than case studies to understand depersonalization.^[2] However, there remains a lack of solid consensus on its definition and scales used for assessment.^[2][14] Salami and colleagues argued that studies of electrophysiological depersonalization-derealization markers are urgently needed, and that future research should use analysis methods that can account for the integration of interoceptive and exteroceptive signals.^[5]

The Depersonalisation Research Unit at the Institute of Psychiatry in London conducts research into depersonalization disorder.^[42] Researchers there use the acronym DPAFU (Depersonalisation and Feelings of Unreality) as a shortened label for the disorder.

In a 2020 article in the Journal Nature, Vesuna, et al. describe experimental findings which show that layer 5 of the retrosplenial cortex is likely responsible for dissociative states of consciousness in mammals.