Dissociative identity disorder

1) The common and scientific name of the disease.

Dissociative identity disorder (DID), more commonly known as multiple personality disorder.

2) What causes it?

Most often, the victim has suffered some sort of mental trauma. They have been forced to develop multiple personalities to cope with stressful situations. Eventually, this separation process gets to a point where the personalities become completely different people, rather than aspects of one person.

3) What are the symptoms? How long do they it last? Is it deadly?

Symptoms of DID include blackouts, finding themselves places that they don't remember going to, and doing things they don't remember. These symptoms last until the victim dies, or they're cured. It's usually not deadly, but there have been cases of suicidal personalities manifesting.

Usually, there are two or more personalities; one that knows about the other personality, while the others are clueless about the other personalities. Usually, the "original" personality doesn't know anything about the others. Furthermore, there is usually no "dominant" personality. There are almost always two or more personalities that often manefest.

4) Can it be cured? If so, how? If not, is there any way that we can at least treat it?

It is supposedly possible, if very difficult, to cure a case of DID. DID occurs when different aspects of a personality fragment, thus, the way to cure it is to get the "original" personality to accept the others as parts of themselves. Since the original personality usually knows nothing about their other personalities, this is usually aided by hypnotisim to "introduce" the personalities to each other.