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  • An Empirical Approach to Understanding Delusions
  • S. Nassir Ghaemi (bio)

“With the growth of psychopharmacology and the development of biochemical and neurophysiological research, the need for careful description of clinical phenomena in psychiatry is greater than ever before.”

(Hamilton 1976)

This view is even more true today than when Frank Fish first stated it in 1967. Given all the research on psychosis in the intervening three decades, it is striking that our understanding of the concept of delusion remains limited. It is often assumed that delusion and normal thinking are qualitatively different. This belief may derive in part from the subjective strangeness, most clearly described by Karl Jaspers (1913), one often experiences when observing a person with delusions. But empirical (Kendler et al. 1983; Oepen et al. 1990) and conceptual (Maher 1990) studies of delusional thinking provide support for the view that delusions lie at the extreme of a continuum of thought content. Much like the label “hypertension,” the decision to use the label “delusion” is somewhat arbitrary, since a qualitative difference at some point appears to be clinically described, whereas the empirical and conceptual evidence suggests only quantitative difference along a continuum.

If we accept this quantitative perspective on delusion, then our understanding of the clinical process of evaluating delusions alters somewhat. Spitzer (1990) has argued that the work of psychopathological research is to clarify the “intension” (intention), or meaning, of concepts by matching them with their extension, or the clinical uses of those concepts, in psychiatric practice. Thus, he holds, psychiatrists in fact know what delusions are, and they are able to clinically utilize their understanding for the benefit of patients, but psychiatrists cannot explain what it is that they are doing. I would suggest that this perspective takes too much for granted clinically. The history of nosology in psychiatry, in fact, largely consists of the correction of erroneous clinical activities by means of empirical research. For example, clinicians diagnosed schizophrenia much differently in the 1950s than in the 1990s in the U.S., and the change can be attributed mainly to empirical studies on the phenomenology, genetics, course, treatment, and pathophysiology of patients with psychotic and affective disorders. These empirical studies changed the “extension” of schizophrenia, and thus the “intension” as well, since what we mean by using the term schizophrenia has also changed. The notion of delusion will also undergo such changes in meaning and [End Page 21] use as more sophisticated empirical studies in psychopathology become available.

With this background, I wish to provide a description of the clinical process of evaluating delusions in the context of the mental status examination. This is based on empirical data supporting a continuum, rather than a categorical perspective on thinking (as noted above), and is supplemented by previous descriptions of clinical psychopathology (Hamilton 1976; Sims 1988) and my own clinical experience. Afterwards, I will discuss the conceptual implications of recent empirical work on delusions.

Examining Thinking in the Mental Status Examination

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Figure 1.

The descriptive continuum of thought content.

The part of the mental status examination that assesses thinking can be divided into two areas: thought content and thought process. Thought content can be described on a continuum of abnormality proceeding from “normal” thought to overvalued ideation, obsession, and then delusion (figure 1).

Overvalued ideation differs from normal thoughts mainly in the degree of conviction or affective tone attached to the thought content. Obsession differs from overvalued ideation in being ego-dystonic, or subjectively distressing, while overvalued ideas are ego-syntonic and not troublesome to the person experiencing them. Similarly, obsessions, being ego-dystonic, differ from delusions, which usually are ego-syntonic. The distinction between delusions and other abnormal thoughts has never been clearly defined, however. A more severe loss of contact with reality appears to be involved, but it is not clear exactly what is necessary and sufficient to define this qualitative difference. On the continuum of abnormality in thought content, the transition to delusion is not clear-cut.

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Figure 2.

The descriptive continuum of thought process.

Thought processes comprise the second half of the mental status examination, and can be described along...