Dissociative Identity Disorder (DID), formerly known as Multiple Personality Disorder, is a dissociative disorder in which a person develops alternating identities. These identities may have unique mannerisms, names, characteristics and voices (i.e.: accents, wearing glasses, differing ages).
According the National Alliance on Mental Illness (NAMI), people who have DID may feel as though multiple voices are trying to take over at once. Many people experience gaps in their memory, including memories of trauma, personal information and daily events.