A delusion, in everyday language, is a fixed belief that is either false, fanciful, or derived from deception.
Psychiatry defines the term more specifically as a belief that is pathological (the result of an illness or illness process) and is held despite evidence to the contrary.
As a pathology, it is distinct from a belief based on false or incomplete information, dogma, stupidity, apperception, illusion, or other effects of perception.
Delusions typically occur in the context of neurological or mental illness, although they are not tied to any particular disease and have been found to occur in the context of many pathological states (both physical and mental).
However, they are of particular diagnostic importance in psychotic disorders and particularly in schizophrenia, paraphrenia, manic episodes of bipolar disorder, and psychotic depression.
Although non-specific concepts of madness have been around
for several thousand years, the psychiatrist and philosopher Karl
Jaspers was the first to define the three main criteria for a belief to
be considered delusional in his 1917 book ''General Psychopathology''.
These criteria are:
- certainty (held with absolute conviction)
- incorrigibility (not changeable by compelling counterargument or proof to the contrary)
- impossibility or falsity of content (implausible, bizarre or patently untrue)
These criteria still continue in modern psychiatric
diagnosis. The most recent Diagnostic and Statistical Manual of Mental
Disorders defines a delusion as:
- A false belief based on incorrect inference about external
reality that is firmly sustained despite what almost everybody 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''.
There is controversy over this definition, as 'despite what
almost everybody else believes' implies that a person who believes
something most others do not is a candidate for delusional thought.
Furthermore, it is ironic that, while the above three criteria are
usually attributed to Jaspers, he himself described them as only
'vague' and merely 'external'. He also wrote that, since the genuine or
'internal' 'criteria for delusion proper lie in the primary experience of delusion and in the change of the personality not
in the above three loosely descriptive criteria, we can see that a
delusion may be correct in content without ceasing to be a delusion, for
instance - that there is a world-war.'.
Furthermore, when a false belief involves a value judgment,
it is only considered as a delusion if it is so extreme as to defy
credibility. Since the delusional conviction occurs on a continuum, it
can be inferred from an individual's behavior many times. A delusion and
an overvalued idea tend to confuse. The latter implies that the
individual has a unreasonable belief or idea but does not hold it as
firmly as when a delusion takes place.
Delusions are not due to a medical condition or substance
abuse and they may seem believable at face value. Also, patients usually
appear normal as long as another person does not touch upon their
delusional themes.
Delusions are not tied to any particular disease and they
usually occur in the context of neurological or mental illness. Also,
they have been found to occur in the context of many pathological
states.
Further Reading
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"Delusion"
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