Dissociation is any of a wide array of experiences, ranging from a mild emotional detachment from the immediate surroundings, to a more severe disconnection from physical and emotional experiences. The major characteristic of all dissociative phenomena involves a detachment from reality, rather than a loss of reality as in psychosis.
Dissociation is commonly displayed on a continuum. In mild cases, dissociation can be regarded as a coping mechanism or defense mechanism in seeking to master, minimize or tolerate stress – including boredom or conflict. At the non-pathological end of the continuum, dissociation describes common events such as daydreaming. Further along the continuum are non-pathological altered states of consciousness.
More pathological dissociation involves dissociative disorders, including dissociative fugue and depersonalization disorder with or without alterations in personal identity or sense of self. These alterations can include: a sense that self or the world is unreal (depersonalization and derealization); a loss of memory (amnesia); forgetting identity or assuming a new self (fugue); and separate streams of consciousness, identity and self (dissociative identity disorder, formerly termed multiple personality disorder) and complex post-traumatic stress disorder.
Dissociative disorders are sometimes triggered by trauma, but may be preceded only by stress, psychoactive substances, or no identifiable trigger at all. The ICD-10 classifies conversion disorder as a dissociative disorder. The Diagnostic and Statistical Manual of Mental Disorders groups all dissociative disorders into a single category and recognizes dissociation as a symptom of acute stress disorder, posttraumatic stress disorder, and borderline personality disorder.
Although some dissociative disruptions involve amnesia, other dissociative events do not. Dissociative disorders are typically experienced as startling, autonomous intrusions into the person's usual ways of responding or functioning. Due to their unexpected and largely inexplicable nature, they tend to be quite unsettling.