Difference between MPD and DID?

Q: What is the difference between Multiple Personality Disorder (MPD) and Dissociative Identity Disorder (DID)? - Anon

A: Mental disorders are named, classified, and described in a book called the Diagnostic and Statistical Manual of Mental Disorders (called the DSM for short). This book is used by doctors, counselors/therapists, and psychiatrists to diagnose behaviors/symptoms, and the book is updated every decade or so to reflect new research, beliefs, understanding of mental illness.

The Diagnostic and Statistical Manual of Mental Disorders (DSM) criteria for Multiple Personality Disorder (MPD) was first established in 1980. The clinical criteria was:

DSM-III Criteria for Multiple Personality Disorder:
A. The existence within the individual of two or most distinct personalities, each of which is dominant at a particular time.
B. The personality that is dominant at any particular time determines the individual's behavior.
C. Each individual personality is complex and integrated with its own unique behavior patterns and social relationships.
D. Two or more alter personalities must exhibit individually distinct and consistent alter personality-specific behavior on at least three occasions.
E. There is evidence of some type of amnesia or combinations of types of amnesia among alter personalities (e.g., one-way amnesia, mutual amnesia, etc.). the amnesia does not have to include all of the alters.

The DSM-IV, which was released in 1994, changed the name of Multiple Personality Disorder to Dissociative Identity Disorder (DID) and changed the criteria to:

DSM-IV Criteria for Dissociative Identity Disorder:
A. The presence of two or more distinct identities or personality states (each with its own relatively enduring pattern of perceiving, relating to, and thinking about the environment and self).
B. At least two of these identities or personality states recurrently take control of the person's behavior.
C. Inability to recall important personal information that is too extensive to be explained by ordinary forgetfulness.
D. The disturbance is not due to the direct physiological effects of a substance (e.g., blackouts or chaotic behavior during Alcohol Intoxication) or a general medical condition (e.g., complex partial seizures). Note: In children, the symptoms are not attributable to imaginary playmates or other fantasy play.

So, according to the DSM, the name Multiple Personality Disorder has been replaced or renamed Dissociative Identity Disorder. Therefore, they are the same and the newer name should be used.

But...

Many people with the disorder may prefer one name over the other, based on:
1. What the disorder was called when they were diagnosed,
2. What name they believe best fits their experience or system of alters,
3. Their stance on if the name was changed just for political reasons inside the psychology field in an attempt to make it less "sensational" or more "palatable" for professionals to admit they treat it.
4. Their personal beliefs that MPD and DID should be used to describe different levels of severity, different causes, and different expectations for the number and amount of differentiations between personalities. Many people seem to think that MPD better describes a more severe form of dissociation, would tend to be caused by more severe or long-lasting trauma events, and that the alters involved would be better defined/more distinct. For example, imagine a glass vase as being an integrated/normal/non-dissociative personality. If you dropped the vase 3 feet and it cracked in a few places, but still held it's overall shape, it would be DID. If you dropped the vase repeatedly, or from a more drastic height, and it shattered or pieces broke off, then that would be MPD.

P.S. I still prefer the term Multiple Personality Disorder, but have had to move towards using Dissociative Identity Disorder more on my blogs and websites due to how search engines function.