Depersonalization-derealization disorder (DPDR, DPD) is a mental disorder in which the person has persistent or recurrent feelings of depersonalization or derealization. Depersonalization is described as feeling disconnected or detached from ones self. Individuals may report feeling as if they are an outside observer of their own thoughts or body, and often report feeling a loss of control over their thoughts or actions. Derealization is described as detachment from ones surroundings. Individuals experiencing derealization may report perceiving the world around them as foggy, dreamlike/surreal, or visually distorted.Depersonalization-derealization disorder is thought to be caused largely by interpersonal trauma such as childhood abuse. Adverse early childhood experiences, specifically emotional abuse and neglect have been linked to the development of depersonalization symptoms. Triggers may include significant stress, panic attacks, and drug use. Those who do have this disorder could be in a depersonalized state for as long as a regular panic attack lasts. However, in some certain situations this state of mind could last either hours, days, and possibly even weeks at a time.Diagnostic criteria for depersonalization-derealization disorder includes persistent or recurrent feelings of detachment from ones mental or bodily processes or from ones surroundings. A diagnosis is made when the dissociation is persistent and interferes with the social or occupational functions of daily life.While depersonalization-derealization disorder was once considered rare, lifetime experiences with it occur in about 1–2% of the general population. The chronic form of the disorder has a reported prevalence of 0.8 to 1.9%.
Studies found that patients with DPD could be distinguished from patients with clinical depression and posttraumatic stress disorder.The vestibular system may also play a role in DPDR. The vestibular system helps control balance, spatial orientation, motor coordination, but also plays a role in self-awareness. Disruption to this system can potentially cause a feeling of detachment from surroundings. Several studies have shown that patients with peripheral vestibular disease are also more likely to have dissociative symptoms when compared to healthy individuals.Dissociative symptoms are sometimes described by those with neurological diseases, such as amyotrophic lateral sclerosis, Alzheimers, multiple sclerosis (MS), etc., that directly affect brain tissue. Diagnosis
Assessment
Diagnosis is based on the self-reported experiences of the person followed by a clinical assessment. Psychiatric assessment includes a psychiatric history and some form of mental status examination. Since some medical and psychiatric conditions mimic the symptoms of DPD, clinicians must differentiate between and rule out the following to establish a precise diagnosis: temporal lobe epilepsy, panic disorder, acute stress disorder, schizophrenia, migraine, drug use, brain tumor or lesion. No laboratory test for depersonalization-derealization disorder currently exists. As patients with dissociative disorders likely experienced intense trauma in the past, concomitant dissociative disorders should be considered in patients diagnosed with a stress disorder (i.e. PTSD or acute stress disorder).The diagnosis of depersonalization disorder can be made with the use of the following interviews and scales:

The Structured Clinical Interview for DSM-IV Dissociative Disorders (SCID-D) is widely used, especially in research settings. This interview takes about 30 minutes to 1.5 hours, depending on individuals experiences.