Schizophrenia vs. Multiple Personality (post 2): If they both have hallucinations and delusions, why is the former psychotic and the latter not?

In the psychiatric diagnostic manual, schizophrenia is in the chapter “Schizophrenia Spectrum and Other Psychotic Disorders” (1, pp. 87-122). Whereas, multiple personality (called “dissociative identity disorder”) is in the chapter “Dissociative Disorders” (1, pp. 291-307). (“Dissociation” refers to altered states of consciousness and compartmentalization.)

Schizophrenia is a psychosis, because the person thinks that his hallucinations and delusions are objectively real and true.

A person with multiple personality is more like a novelist. He may hear the voices of his alternate personalities or characters, and see them in “waking dreams”—and these hallucinations may be experienced as “more real than real”—but he ultimately understands that other people don’t see and hear these things, and that the personalities are not really separate people. So it might be more accurate to call them pseudohallucinations and pseudodelusions.

Although a person with multiple personality has various personalities who are totally convinced that they are separate, autonomous people, the person’s regular, “host” personality sees life in an ordinary way. Indeed, the host personality often has no awareness that there are any other personalities. Or, if he is aware of other personalities, he may think of them in other terms, such as a “guardian angel” or “muse.” But most often he knows nothing about it. He might occasionally notice a memory gap, but it usually does not cause a problem; it makes no sense; there is nothing he can do about it; he suspects it happens to everyone; so he just ignores it.

But, you might wonder, doesn’t a person with multiple personality look crazy? Doesn’t switching from one personality to another look bizarre? It would, if that were the way a person with multiple personality usually looked. But that kind of behavior is seen only a) in a demonstration interview, in which, for educational or other reasons, a person who knows he has multiple personality is intending to put his personalities on display, or b) in therapy for multiple personality. Otherwise, you will usually not know that a person has multiple personality from their overt behavior.

Why won’t you know? First, you are most likely to be seeing only the host personality (see above). Second, if alternate personalities do come out, they almost always do so incognito. That is why you need clues to suspect that a person has multiple personality, such as a puzzling inconsistency and a history of memory gaps.

Once you do discover the alternate personalities, and they know that you know, and especially once you know their names, then it all becomes quite overt and obvious. The diagnosis is not, stress not, a psychoanalytic interpretation. It is observed. It is made when you have knowingly seen the personality switches and actually conversed with the alternate personalities.

But this blog is not primarily about mental illness and diagnosis, which I discuss occasionally only to clarify certain concepts. What interests me is that for every person who has the mental illness, multiple personality disorder, there are probably thirty people who have a normal version.

1. American Psychiatric Association: Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition [DSM-5]. Arlington VA, American Psychiatric Association, 2013.