Yes, multiple personality disorder is a real disease, because there are people who actually think that they are different people. Those with multiple personality disorder cannot be taught to control when their other personalities appear. This disease of the mind has been studied and confirmed by psychologists, including those from the government.
Multiple personality disorder is definitely a real disease. This has been proven time and time again, from several medical professionals including: neurologists, neuroscientists, psychiatists, and psychologists. It has been documented, observed, and tested. So yes, it is a real disease and there is no question as to how real it is.
There is no disease by the name "multiple personality disorder" so I can make easy work of this question and say no. There is, however, a mental condition called Dissociative Identity Disorder which is what people are referring to when they say that other thing. It is a real thing, it's very complex, and it's not something people without doctorates in psychiatry have any business calling real or fake.
I believe multiple personality disorder is most often a psychological condition that can be treated with counseling or medication, I think that anyone who is suffering from a multiple personality disorder should at least visit a doctor and speak their concerns with them the doctor will best know how to proceed from there.
No, I do not feel like this is a real disease at all. I think that the person can just go through mood swings, and that they are not actually going through a different personality that they have. I think that it is foolish to think that they do this.