Patients with dissociative identity disorder (DID) are often unaware of the condition when they first visit a physician. Instead, they are likely to seek 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.

In addition, a physician may ask questions such as:

• Are they unable to recall previous events?
  
  
• Do they sometimes meet unfamiliar people who claim to know them?
  
  
• Have they found themselves at a location without knowing how they got there?
  
  
• Have they found any items they do not recall purchasing?
  
  
• Are they depressed? Do they engage in self-injurious behavior or have suicidal thoughts?
  
  
• Do they experience auditory (hearing) or visual (seeing) hallucinations?

A general physician may refer a patient to a psychiatrist. Because DID is closely associated with childhood trauma, the physician will attempt to obtain enough information from the patient to create a clear outline of the patient’s trauma history. The physician will also inquire about symptoms of post-traumatic stress disorder (PTSD) – such as flashbacks and nightmares – because the condition is often associated with DID. 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 in some cases may be the primary source of symptoms.

DID is diagnosed when a patient has at least two distinct personalities (or alters), each of which has a lasting pattern of sensing, thinking about and relating to the self and the environment. At least one of the alters must also come to the fore to control a patient’s behavior, and a patient’s inability to remember cannot be explained by ordinary forgetfulness. In addition, other factors – including substance abuse or a medical condition (e.g., complex partial seizures) – cannot be responsible for the patient’s unusual behavior.

Diagnosing DID in children can be difficult. Symptoms are often less distinct in children than they are in adolescents or adults. In addition, DID should not be diagnosed if symptoms can be attributed to imaginary friends or other fantasy play.