Previously known as multiple personality disorder (MPD), dissociative identity disorder (DID) is a very rare dissociative disorder in which two or more distinct identities (alters) control a patient’s thoughts and behaviors. DID is thought to result from a failure or inability to integrate identity, memory and consciousness. Patients with this condition have gaps in memory or an inability to remember important personal information. A patient’s passive identities have less complete memories than their aggressive personalities.

Dissociation is a psychological defense mechanism in which anxiety-provoking thoughts, emotions or physical sensations are separated from the rest of the psyche. Patients with DID may have 100 or more identities, although about half of all patients experience 10 or fewer identities. Just one personality controls a patient’s behavior at any given time, each distinct personality may have its own name, personal history and self-image. Psychosocial stress often triggers the transition from one identity to another. In most cases, these changes take just seconds, although the transition can be more gradual.

Childhood trauma (e.g., from physical, sexual or emotional abuse) is believed to be the chief trigger of DID. Patients with DID are frequently unaware that they have the condition and may seek medical help because of unexplained episodes of memory loss. A physician will perform a complete physical examination and compile a thorough medical history while trying to determine the cause of this memory loss.

During the physical evaluation, patients will be asked to recount a complete history of symptoms, including when they started, how long they have lasted and how severe they are. It is also noted whether the patient has had these symptoms before and, if so, whether and how they were treated. In addition, other tests and questioning may be performed to rule out other conditions – such as schizophrenia, bipolar disorder, anxiety disorders or factitious disorders – that may be the source of symptoms.

Psychotherapy is the primary treatment for DID. In most cases, patients are encouraged to remember any trauma they may have repressed and to gradually work through it. There are no medications specifically intended to treat DID. However, some medications used to treat other disorders (e.g., antidepressants, anti-anxiety medications) may be helpful.