You are correct that dissociative disorders are not the same as personality disorders, and the term "multiple personality disorder" is outdated and misleading. The confusion arises from historical reasons and the evolution of psychiatric understanding.
The term "multiple personality disorder" was used in the past to describe what is now known as Dissociative Identity Disorder (DID). It was first introduced in the late 19th century and gained significant attention in the 20th century. At that time, mental health professionals believed that individuals with DID had distinct, separate personalities (or "alters") that were entirely independent and could take control of the person's behavior and thoughts.
However, as research and understanding progressed, it became apparent that DID is not about having multiple distinct personalities. Instead, it involves the presence of different states of consciousness, which are often referred to as "alters" or "identity states." These identity states can have distinct characteristics, memories, emotions, and behaviors, but they are all part of the same person.
The term "Dissociative Identity Disorder" (DID) was introduced to replace "multiple personality disorder" to reflect this change in understanding. The focus shifted from a notion of separate personalities to one of dissociation, where an individual's sense of self, memory, and consciousness can be fragmented or divided.
It is essential to use accurate and updated terminology in the field of mental health to promote better understanding and avoid stigmatization or misinterpretation of conditions. While the term "multiple personality disorder" is still occasionally used in popular media or by the general public due to its historical significance, mental health professionals primarily use "Dissociative Identity Disorder" (DID) when diagnosing and referring to this condition.