Dissociative Disorders

DID

Dissociative identity disorder is the disorder that was previously recognized as multiple personality disorder. It is characterized by the presence of two or more dissociated self states that have the ability to take executive control and are associated with some degree of personal amnesia.³ For the diagnostic criteria for DID according to the DSM-5, see here.

OSDD

Other specified dissociative disorder (OSDD) is a dissociative disorder that serves as a catch-all category for symptom clusters that do not fit neatly within another dissociative disorder diagnosis. This diagnosis was known as dissociative disorder not otherwise specified (DDNOS) before the DSM-5. Both OSDD and DDNOS contain(ed) examples of specific possible symptom clusters within the diagnosis. These examples were and often still are used as subtypes of the disorder.³

OSDD-1a

Those with OSDD-1a have dissociative parts that are not sufficiently differentiated to qualify as alters. For individuals with OSDD-1a, dissociated parts are more likely to present as the same individual at different ages, as the same individual in different modes, or as different versions of the same individual.³

OSDD-1b

Those with OSDD-1b do not have strict amnesic barriers between alters. An individual with OSDD-1b has a subjectively continuous memory; different alters do not have different versions of their history for daily life because all relevant information is accessible to all alters.³ Instead, amnesia is formed through emotional recall: all remember events, but each part feels differently—or not at all—about what has transpired.

OSDD-1

There are some whose symptoms do not fall neatly into either the category of OSDD-1a or OSDD-1b. In these cases, the diagnosis OSDD-1 is used.

Partial DID

The diagnosis Partial DID comes from the ICD-11, which is a different diagnostic manual than the DSM-5-TR. The ICD-11 diagnosis "Partial DID" is limited to presentations in which dissociated parts engage in very constricted behaviors. The ICD-11 but not DSM-5-TR differentiates between DID-like presentations in which an individual attributes their experiences to possession by an external entity (possession trance disorder).

DID vs. OSDD: What's the Difference?

When questioning, it can be difficult to figure out if you have DID or OSDD. What’s the difference between the two? How can you tell? A general rule of thumb is that if an individual has amnesia between parts and there are two or more parts that have an independent sense of self, DID is diagnosed. If amnesia is present but parts do not have a clearly identified sense of self, then OSDD-1a is diagnosed. If amnesia is not present but parts do have a clearly identified sense of self, then OSDD-1b is diagnosed.

To be clear:
YES AMNESIA, YES PARTS - DID
NO AMNESIA, YES PARTS - OSDD-1b
YES AMNESIA, NO PARTS - OSDD1a

Indications that parts have an independent sense of self can include parts presenting with their own names; genders; sexualities; or other identity traits, or parts having internal communication and relationships with each other³.

In general, individuals with DID score higher on measures of depersonalization, derealization, dissociative amnesia, identity confusion, identity alteration, and somatization compared to individuals with OSDD-1. For those with OSDD-1 that switch between alters, switching is less likely to be spontaneous. Research suggests that individuals with OSDD-1 may also have fewer comorbid mental health conditions¹⁰.