Today, NAMI put out a helpful fact sheet on Dissociative Disorders:
What is dissociation?
A number of people with mental illnesses experience dissociation: a disturbance of thinking, awareness, identity, consciousness or memory. Dissociation is more severe than just ordinary forgetfulness and is also not associated with any underlying cause of memory deficits or altered consciousness (e.g., neurological illnesses, substance or alcohol abuse). Some people have dissociative events that last only moments where as others experience extended periods of dissociation.