Dissociative Identity Disorder
There are many misconceptions about "Split Personalities." Schizophrenia, for example, is an often misused label, and refers to a different mental disorder.
What is commonly thought of as being a "split personality" is actually known as dissociative identity disorder or multiple personality disorder. People with this disorder have at least one "alter," or identity, separate from the original. The alters can vary in age, gender, personality and race, among other things.
Often, a person with DID will be unable to remember some of the events that occurred during episodes
with one of his or her alters. Although this site plays on "split personality" stereotypes to make
a fun, creative costume, the reality for people with DID can be frightening and uncomfortable. Many
people diagnosed with DID also experience depression and are at risk for self-harm and suicide.
This information was found at the National Alliance on Mental Illness and WebMD's entry on Dissociative Disorder.