Disorientation is the loss of awareness of self, place and/or time.
Dissociation is the ... separation of the emotional self from the awareness of self, place and/or time. It is a short-term event, most commonly seen in response to severe trauma, but also occurring in normal situations, such as losing track of time while reading. If it persists, or is recurrent, especially at a young age, a Dissociative Disorder develops. Dissociation sits nicely in the field of neuropsychiatry - it's causes are primarily psychosocial, yet the physical pathology well known and the symptoms reproduceable upon neural stimulation - and my leaning towards a physical basis underlying all psychiatric disorders, along with the initial use of the term to refer to symptoms secondary to emotional trauma (eg shell-shock/PTSD) resulted in my comment that it developed from the field of neurology.
Or something like that.
