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| Kengo Miyazono |
Is the definition of delusion really different between DSM-5 and DSM-IV?
In DSM-5, definitional remarks on delusion appear twice; first, in "Schizophrenia Spectrum and Other Psychotic Disorders" in Section II (p.87) and, second, in "Glossary of Technical Terms" in Appendix (p.819). So, we need to look at both of them and compare them to their counterparts in DSM-IV.
Let us begin with "Glossary", which is usually taken to be giving the official definition by DSM.
A false belief based on incorrect inference about external reality that is firmly held despite what almost everyone else believes and despite what constitutes incontrovertible and obvious proof or evidence to the contrary. The belief is not ordinarily accepted by other members of the persons's culture or subculture (i.e., it is not an article of religious faith). When a false belief involves a value judgment, it is regarded as a delusion only when the judgment is so extreme as to defy credibility. Delusional conviction can sometimes be inferred from an overvalued idea (in which case the individual has an unreasonable belief or idea but does not hold it as firmly as is the case with a delusion). (DSM-5, p.819)
A false belief based on incorrect inference about external reality that is firmly sustained despite what almost everyone else believes and despite what constitutes incontrovertible and obvious proof or evidence to the contrary. The belief is not one ordinarily accepted by other members of the person's culture or subculture (e.g., it is not an article of religious faith). When a false belief involves a value judgment, it is regarded as a delusion only when the judgment is so extreme as to defy credibility. Delusional conviction occurs on a continuum and can sometimes be inferred from an individual's behavior. It is often difficult to distinguish between a delusion and an overvalued idea (in which case the individual has an unreasonable belief or idea but does not hold it as firmly as is the case with a delusion). (DSM-IV, p.765) (p.821 in DSM-IV-TR)
Although some changes have been made in the last part of the quotes, they don't seem to be very different. Especially, no changes have been made in response to the problems repeatedly raised for the definition in DSM-IV; delusions do not have to be "false", that delusions do not have to be "about external reality", delusions might not be "based on incorrect inference", and so on.
Let us move on to "Schizophrenia Spectrum and Other Psychotic Disorders".
Delusions are fixed beliefs that are not amenable to change in light of conflicting evidence. Their content may include a variety of themes (e.g. persecutory, referential, somatic, religious, grandiose). Persecutory delusions (i.e., belief that one is going to be harmed, harassed, and so forth by an individual, organization, or other group) are most common. Referential delusions (i.e., the belief that certain gestures, comments, environmental cues, and so forth are directed at oneself) are also common. Grandiose delusions (i.e., when an individual believes that he or she has exceptional abilities, wealth, or fame) and erotomanic delusions (i.e., when an individual believes falsely that another person is in love with him or her) are also seen. Nihilistic delusions involve the conviction that a major catastrophe will occur, and somatic delusions focus on preoccupations regarding health and organ function. (DSM-5, p.87)
Delusions (Criterion A1) are erroneous beliefs that usually involve a misinterpretation of perceptions or experiences. Their content may include a variety of themes (e.g., persecutory, referential, somatic, religious, or grandiose). Persecutory delusions are most common; the person believes he or she is being tormented, followed, tricked, spied on, or subjected to ridicule. Referential delusions are also common; the person believes that certain gestures, comments, passages from books, newspapers, song lyrics, or other environmental cues are specifically directed at him or her. The distinction between a delusion and a strongly held idea is sometimes difficult to make and depends on the degree of conviction with which the belief is held despite clear contradictory evidence. (DSM-IV, p.275) (DSM-IV-TR (p.299) is almost the same)
My impression is that they are, again, not very different overall.
One difference is that DSM-IV says that delusions are "erroneous beliefs", while DSM-5 says that they are "fixed beliefs". This would be a nice change, because "erroneous" probably implies "false", but delusions do not have to be false.
Another difference is that DSM-IV says that delusions involve a misinterpretation of perceptions or experience. This "empiricist" commitment is removed in DSM-5. This might be a good thing, because people might want DSM to be independent from theoretical issues like empiricism.
Lisa says that DSM-5 narrows the gap between delusions and other irrational beliefs. But, this is not obvious. The change from "erroneous belief" to "fixed belief" doesn't seem to narrow the gap between delusions and other irrational beliefs. Again, eliminating empiricism doesn't seem to narrow the gap. Lisa might think that the following sentence in DSM-5, which comes in the paragraph following the one quoted above, narrows the gap.
But, actually, the last sentence of the quote from DSM-IV above says almost the same thing. Also, it is not obvious that the "strongly held idea" in the sentence includes everyday irrational beliefs that Lisa is talking about.
Summing up, although there are some minor changes between DSM-5 and DSM-IV, including some good ones, they are not remarkably different. Especially, no changes have been made in "Glossary" in response to the problems that have been raised for DSM-IV...