Derealization

# Overview
Derealization (DR) is an alteration in the perception or experience of the external world so that it seems strange or unreal. Other symptoms are feeling as though one's environment is lacking in spontaneity, emotional colouring and depth.  .  It is a dissociative symptom of many conditions, such as psychiatric and neurological disorders, and not a standalone disorder. It is also a transient side effect of acute drug intoxication, sleep deprivation and stress.
Depersonalization is a subjective experience of unreality in one's sense of self, while derealization is unreality of the outside world.  Depersonalization and derealization are often used interchangeably, although evidence suggests they have distinct neurobiological mechanisms.  Chronic derealization may be caused by occipital-temporal dysfunction.
These symptoms are common in the population, with a lifetime prevalence of up to 74% and between 31-66% at the time of a traumatic event.

# Description
The detachment of derealization can be described as an immaterial substance that separates a person from the outside world, such as a sensory fog, a pane of glass, or a veil. Individuals may complain what they see lacks vividness and emotional colouring. Emotional response to visual recognition of loved ones may be significantly reduced. Feelings of deja vu or jamais vu are common. Familiar places may look alien, bizarre, and surreal. Such perceptual abnormalitites may also extend to the senses of hearing, taste, and smell.
Another symptom of this condition can be the constant worrying or strange thoughts that people find hard to switch off.  Derealization builds up slowly with the underlying anxiety, but shows itself suddenly, often after a panic attack, and is then difficult or impossible to ignore until the sufferer receives treatment. This type of anxiety can be crippling to the sufferer and may lead to avoidance behaviour. Sufferers may experience great concern over the cause of their derealization. It is often difficult to accept that such a disturbing symptom is simply a result of anxiety, and the individual may often think that the cause must be something more serious.  This can in turn cause more anxiety and worsen the derealization.

# Causes
Derealization can accompany the neurological conditions of epilepsy, migraine, and mild head injury. There is a similarity between visual hypoemotionality, a reduced emotional response to viewed objects, and derealization. This suggests a disruption of the process by means of which perception becomes emotionally coloured.  This qualitative change in the experiencing of perception may lead to the reports of anything viewed being unreal or detached.
Derealization can also be caused by vestibular disorders such as labyrinthitis and vestibular neuronitis because the brain is receiving mixed signals from the vestibular nerves due to damage or infection, and so causes the brain to function slower and create feelings of unreality.
Cannabis, hallucinogens, antidepressants and nicotine can all produce feelings resembling derealization, particularly when taken to excess. It can also result from alcohol or benzodiazepine withdrawal.
Derealization can also be a symptom of severe sleep disorders, mental disorders such as depersonalization disorder, borderline personality disorder, schizophrenia, and anxiety disorders.