DID vs OSDD-1a vs OSDD-1b

Hi all!

This is an informative quick run-through about the differences among Dissociative Identity Disorder (DID), Other Specified Dissociative Disorder-1a (OSDD-1a) and Other Specified Dissociative Disorder-1b (OSDD-1b). Kind of a one-minute quick bite if you may.

OSDD-1a and OSDD-1b is under the catch-all umbrella of OSDD-1. OSDD-1 is the subtype of Dissociative Disorders that is most closely related to DID but do not meet the required set of diagnostic criteria for DID. And from OSDD-1, we have OSDD-1a and OSDD-1b.

OSDD-1a

Generally speaking, individuals with OSDD-1a have two or more parts that identifies with each other as the same person, but with different "modes" e.g. a work part, a play part, a family part, a child part, etc. They do not lose a "sense of self" and maintains self-identity across all parts. The parts often present themselves as different ages (relative to the body's age), different 'versions' of themselves, or different 'modes' of themselves. People with this disorder also experience amnesia.

OSDD-1b

Generally speaking as well, individuals with OSDD-1b usually have two or more highly distinctive parts/alters (like in DID) who may have different names, ages, gender, preferences, etc. but have near zero or zero amnesia for the body's past or in day-to-day life. The amnesia barrier found in DID systems is near zero or zero in individuals (systems) with OSDD-1b. Treatment for individuals with OSDD-1b is the same as individuals (systems) with DID. The discontinuities of Sense of Self and Sense of Agency in OSDD-1b individuals (systems) is similar to individuals (systems) with DID.

DID

Individuals (systems) with DID have two or more distinct parts/alters with marked discontinuities of Sense of Self and Sense of Agency, and may or may not follow with dissociative amnesia when another part/alter have "fronted" during that period of time, depending on level of consciousness of the different parts/alters involved. However, dissociative amnesia for large gaps of the body's past and/or important/key life events e.g. a divorce, a graduation, a loss of a best friend, etc. as well as day-to-day life is a diagnostic criteria for DID, as compared to OSDD-1b. The level of dissociative amnesia may vary between parts/alters and/or severity of the triggering event, if any/applicable.

Sources:

American Psychiatric Association. (2022). Diagnostic and statistical manual of mental disorders (5th ed., text rev.). https://doi.org/10.1176/appi.books.9780890425787

Dell, P. F., & O'Neil, J. A. (2009). The long struggle to diagnose multiple personality disorder (MPD): Partial MPD. In Dissociation and the dissociative disorders: DSM-V and beyond. New York: Routledge.

Hart, O., Nijenhuis, E. R. S., & Steele, K. (2006). The haunted self: Structural dissociation and the treatment of chronic traumatization. New York: W.W. Norton.