Delusions can be reliably identified in clinical populations. However their definition has been a matter of controversy. Attributes that are commonly used to characterise delusions, such as falsity and excessive conviction, do not generally distinguish them from more ordinary beliefs. The convention that considers delusions as forms of belief obscures many of the important points of distinction from more ordinary beliefs.
Conceptual review of the concept of bizarre delusions suggests that delusions are distinguishable from other forms of belief by virtue of their individual bizarreness. That is, delusions depart from what might be the understandable beliefs or experiences for a given individual. Departure from what is objectively possible or culturally sanctioned or expected are useful, but potentially misleading, proxies for individual bizarreness. Although individual bizarreness may be the key defining feature of delusional phenomena, bizarreness, however conceived, may not usefully distinguish different subtypes of delusion.
The idea that delusions are best considered to be on a continuum with more ordinary beliefs is problematic. The continuum hypothesis depends on overemphasis on falsity and complete conviction as identifying characteristics of delusions. Both continuum and category approaches to delusions have utility that depends on the immediate purpose, but neither approach in itself can be presumed to show the greater verisimilitude.
Overvalued ideas are another group of strongly held beliefs that may be false and idiosyncratic. Their relationship to delusions has been uncertain. It is argued that overvalued ideas and delusions are different kinds of phenomena, as overvalued ideas lack the individual bizarreness of delusions. A comparison of delusions in individuals with schizophrenia, with over-valued ideas in individuals with non-psychotic mental disorders, is reported. Several differences between delusions and over-valued ideas were identified. Over-valued ideas were associated with more gradual onset, greater preoccupation, and more concern about the opinions of others about the belief. Delusions were less plausible in their content and the deluded individuals often accounted for the origin of their delusion by referring to other psychotic experiences such as hallucinations. Conviction and insight were not found to differ across the two groups.
Delusions are experiences that have many of the external characteristics of ordinary human belief. However overemphasis on these similarities results in neglect of important differences, and may lead to clinical error.
| Identifer | oai:union.ndltd.org:ADTP/217351 |
| Date | January 2006 |
| Creators | Mullen, Richard Steven, n/a |
| Publisher | University of Otago. Dunedin School of Medicine |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | http://policy01.otago.ac.nz/policies/FMPro?-db=policies.fm&-format=viewpolicy.html&-lay=viewpolicy&-sortfield=Title&Type=Academic&-recid=33025&-find), Copyright Richard Steven Mullen |
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