Dissociation in Psychiatry

Dissociation is a common experience.  At it's least, it's called 'day dreaming'. It refers to the experience of disconnecting our mental processes from the physical experience we are presently in.  At it's most severe expression there are multiple personality disorders, fugue states and flashbacks.
It's called a 'defence' or 'coping mechanism' and refers to an 'altered state of consciousness".
Hypnosis induces a 'dissociative state'.  It's also called 'compartmentalization of experience.
Normally a person is 'integrated' in regards to thoughts, emotion and bodily awareness.
In the dissociative state a person may not be aware of their objective reality but be solely focussed on their subjective reality.
In some dissociative experiences there is loss of memory associated with the altered state of consciousness. This is not necessary as a person experiencing a 'flashback' may have a complete memory of the point they experienced the 'derealization' , one of the terms used to describe the disociative experience, the experienced and the return to normal consciouness and awareness.
Dissociatiion is associated with trauma.  In early childhood trauma personality is not so coalesced. This is the explanation for the phenomena of mutliple personality now termed Dissociative Personality Disorder.  A person may develop an alter ego to cope with trauma.
In rape survivors they may experience flashbacks and react to normal person's as if they were a 'proto rapist'. Unfortunately the dissociative behaviour of people who have been traumatized can itself initiate recurrence of the truam.
Dissociative amnesia refers to the complete blocking out of a traumatic episode. This more commonly occurs with victims but can be a contributing factor in victimizers.
Conversion Disorders have been associated with dissociation.
Psychoactive drugs can also induced a dissociative state temporarily.