The Concepts of Psychiatry: A Pluralistic Approach to the Mind and Mental Illness

13 Dimensions versus Categories

C H A P T E R 1 3 Dimensions versus Categories The follow-up is the great exposer of truth, the rock on which many fine theories are wrecked and upon which better ones can be built. It is to the psychiatrist what the postmortem is to the physician. —P. D. SCOTT Mood and Psychotic Disorders 1. Categorical knowledge involves all-or-nothing qualitative phenomena; that is, something either belongs to category X or to category Y. An example is pregnancy ; one either is or is not pregnant. Dimensional knowledge is continuous and is characterized by possessing or experiencing more or less of something. An example is blood pressure. Every living human has blood pressure; in some it is high, in some low, and in most in between. One of the criticisms that has been made of the evolution of psychiatric nosology after DSM-III is that diagnosis has become hypercategorical. It has been suggested that we have gone too far in trying to categorize psychiatric diagnoses. There are too many diagnoses now, it is alleged, practically one for every mental symptom. This is an exaggeration, but it may hide a deeper truth. Historically, before the shift in nosology that occurred in mainstream psychiatry with DSM-III in 1980, mainstream psychiatry went to an extreme in the dimensional direction. Influenced by certain psychoanalytic doctrines, many individuals in the field held that the only partial dichotomy in diagnosis was between neurosis and psychosis. Everyone was a little bit neurotic, and only more severe forms seemed problematic . Some people, such as Harry Stack Sullivan, even held that psychosis was not an all-or-none phenomenon and that psychotic-like thinking was not unusual in normal (i.e., mildly neurotic) persons (1953). Another view was that everyone is somewhat depressed and that depression thus is not a categorically abnormal phenomenon. (Freud once said that he simply wanted to replace the abnormal misery of mankind with normal unhappiness.) I will discuss the useful aspects of some of these psychoanalytic ideas, but the disadvantages should be obvious. DSM-III was a reaction to this hyperdimensionalism, which prevented psychiatrists from diagnosing individuals who might be treated with newly emerging antidepressant and antipsychotic medications. Has DSM gone too far? Probably. But a reversion to pre-DSM-III hyperdimensionalism is not the solution. 2. Some argue that the major mental illnesses (schizophrenia and manicdepressive illness) are not categorical. The straw man that these opponents of the current nosology prefer to battle is Kraepelin’s nosology. Kraepelin, it may be recalled, designated schizophrenia and manic-depressive illness as the two main disorders in psychiatry. He felt that the concept of manic-depressive illness subsumed all affective disorders (what we might call today bipolar disorder , unipolar depression, cyclothymia, and dysthymia), and he believed that the concept of schizophrenia subsumed all cases of chronic psychosis in which there were no affective symptoms at all (nonaffective psychosis). The Kraepelinian straw man is the view that all psychiatric conditions should be divisible into one of these two categories: schizophrenia (nonaffective psychosis) and manic-depressive illness (affective illness). The reason this is a straw man is that Kraepelin, being an astute clinician, realized that borderline cases existed. He presaged later views of a spectrum of affective illness, for example, in which mild versions of mood disorders (like hypomania) merged with personality traits of mood instability (like cyclothymia). He also recognized mild versions of schizophrenia, which also merged with personality traits (such as, in today’s terminology, schizotypal personality disorder). Another reason a pure dichotomy is a conceptual straw man is that we know that most individuals fall somewhere on a normal curve when diagnostic criteria are applied to their psychiatric symptoms. This is common in some other medical conditions as well, such as hypertension. For instance, most patients who have nonaffective psychosis will not have symptoms of their illness or features of the course of their illness in common with most patients who have affective disorders. But as in a normal curve, there will be overlap at the extremes (see fig. 13.1). The fact that there is overlap at the extremes does not invalidate the concept that in general these two peaks of symptom and course characteristics differ from each other. In this respect, this difference is similar to the situation 186 Practice with populations of individuals that form species (see chapter 7). From a Darwinian perspective, those populations...