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(from DSM-IV and ICD-10 where available)


"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.



“This term has historically received a number of different definitions, none of which has achieved universal acceptance. The narrowest definition of psychotic is restricted to delusions or prominent hallucinations, with the hallucinations occurring in the absence of insight into their pathological nature. A slightly less restrictive definition would also include prominent hallucinations that the individual realizes are hallucinatory experiences. Broader still is a definition that also includes other positive symptoms of Schizophrenia (i.e., disorganized speech, grossly disorganized or catatonic behavior). Unlike these definitions based on symptoms, the definition used in DSM-II and ICD-9 was probably far too inclusive and focused on the severity of functional impairment, so that a mental disorder was termed psychotic if it resulted in ‘impairment that grossly interferes with the capacity to meet ordinary demands of life.’ Finally, the term has been defined conceptually as a loss of ego boundaries or a gross impairment in reality testing. Based on their characteristic features, the different disorders in DSM-IV emphasize different aspects of the various definitions of psychotic.” (DSM-IV, p. 770).

“Psychotic…indicates the presence of hallucinations, delusions, or a limited number of several abnormalities of behavior, such as gross excitement and overactivity, marked psychomotor retardation, and catatonic behavior.” (ICD-10 Classification of Mental and Behavioral Disorders, p. 3-4). In various diagnoses psychotic disorder may also be characterized by “perceptual disturbances” and “abnormal affect”(ICD-10 International Statistical Classification of Diseases and Related Health Problems (pp. 2,329,330).)



“An unreasonable and sustained belief that is maintained with less than delusional intensity (.i.e., the person is able to acknowledge the possibility that the belief may not be true). The belief is not one that is ordinarily accepted by other members of the person’s culture or subculture.” DSM-IV, p.769.



In these definitions, the idea that obsessive thoughts are unrealistic is implicit, and they are tacitly compared with delusions, from which they are distinguished by epistemological criteria (eg. insight into their origin in one's own mind, etc.).- Ed.

"Obsessions are persistent ideas, thoughts, impulses, or images that are experienced as intrusive and inappropriate and that cause marked anxiety or distress. [They are]"ego-dystonic". This refers to the individual's sense that the content of the obsession is alien, not within his or her own control, and not the kind of thought that he or she would expect to have. However, the individual is able to recognize that the obsessions are the product of his or her own mind and are not imposed from without (as in thought insertion)..

The most common obsessions are repeated thoughts about contamination (e.g., becoming contaminated by shaking hands), repeated doubts (e.g. wondering whether one has performed some act such as having hurt someone in a traffic accident...), a need to have things in a particular order (e.g. intense distress when objects are disordered or asymmetrical), aggressive or horrific impulses (e.g. to hurt one's child...), and sexual imagery (e.g. a recurrent pornographic image). [Obsessions] are not simply excessive worries about real-life problems...and are unlikely to be related to a real-life problem.

The individual with obsessions usually attempts to ignore or suppress...or neutralize them with some other thought or action (i.e., a compulsion). For example, an individual plagued by doubts about having turned off the stove attempts to neutralize them by repeatedly checking to ensure that it is off." DSM-IV, p.418.

"Obsessional thoughts are ideas, images, or impulses that enter the patient's mind again and again in a stereotyped form. They are almost invariably distressing and the patient often tries, unsuccessfully, to resist them. They are, however, recognized as his or her own thoughts, even though they are involuntary and often repugnant." ICD-10 International Statistical Classification of Diseases and Related Health Problems, p.342.



Filling in gaps of memory or conscious knowledge with erroneous information. An example of a confabulation would be the belief on the part of a stroke patient that his paralyzed arm belongs to someone else.

"...The confabulator often appears to be unable to recognize the erroneous nature or absurdity of his statements even in the face of painfully (seemingly) apparent contradictory evidence...Presumably, there is no "conscious" attempt on the part of the confabulator to deceive or lie...he apparently believes his own misstatements, which are reported with 'rocklike certitude'..." (Joseph, 1986, p. 508).



DSM-IV is the current version (fourth edition) of the American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders (APA: Washington, 1994). ICD-10 is the current version (tenth revision) of the International Statistical Classification of Diseases and Related Health Problems, developed by the World Health Organization (WHO: Geneva, 1992).