DIAGNOSING PSYCHOLOGICAL DISORDERS:The categorical approach, Prototypical approach

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Abnormal Psychology PSY404

LESSON 16

DIAGNOSING PSYCHOLOGICAL DISORDERS

The term classification refers to any effort to construct groups or categories and to assign objects or people

to these categories or groups on the basis of their attributes, characteristics or relations. Methods of

classification include:

Classical categorical system

Dimensional system

Prototypical approach

In order to classify the psychological disorders we need a classification system. The term classification refers

to process to construct categories and to assign people to these categories on the basis of their attributes or

relations. Classification in scientific context refers to taxonomy. It also refers to nomenclature, which

describes the names and labels that may make up a particular disorder such as schizophrenia or depression.

Classification is at the heart of every science. If we can not label and order objects or experiences or

behaviors scientists could not communicate with one another and our knowledge will not advance.

Therefore, we develop a system with which we could define or classify behavior. Abnormal psychology is

based on the assumption that a behavior is part of one category or disorder and not of another one.

Psychologists use three approaches or strategies to classify disorders:

The categorical approach

Dimensional approach

Prototypical approach

The categorical approach

It was Kraepelin, the first psychiatrist to classify psychological disorders from a biological or

medical point of view. For Kraepelin in term of physical disorders, we have one set of causative factors

which do not overlap with other disorders. We have one defining criteria, which every body in the category

or in the group should meet.

Example Schizophrenia

Dimensional Approach

A second strategy is a dimensional approach, in which we note the variety of cognitions, moods,

and behaviors with which the patient presents and quantify them on a scale. For example, on a scale of 1 to

10, a patient might be rated as severely anxious (10), moderately depressed (5), and mildly manic (2) to

create a profile of emotional functioning (10, 5, 2). Although dimensional approaches have been applied to

psychopathology, they are relatively unsatisfactory.

Prototypical approach

A third approach, for organizing and classifying behavioral disorders which is an alternative to the

first two. It is called a prototypical approach. It identifies some essential characteristics of a disorder and it

also allows for certain non-essential variations that do not necessarily change the classification. With this

approach classifying the disorder by different possible features or properties any candidate must meet (but

not all) of them to fall in that category. In depression, there are five important symptoms such as:

Depressed mood all of the day

Weight loss

Insomnia

Fatigue

Feeling of worthlessness

Abnormal Psychology PSY404

For a person might have three or four of the characteristics of the depression but not all five of them. Yet

we still diagnose the person as depressed.

Categories versus Dimensions

· After a category has been defined, an object is either a member of the category or it is not. A

categorical approach to classification assumes that distinctions among members of different

categories are qualitative.

· In other words, the differences reflect a difference in kind (quality) rather than a difference in

amount (quantity).

· An alternative, scientists often employ a dimensional approach to classification--that is, one

that describes the objects of classification in terms of continuous dimensions.

· Rather than assuming that an object either has or does not have a particular property, it may be

useful to focus on a specific characteristic and determine how much of that characteristic the object

exhibits.

From Description to Theory

· Mental disorders are currently classified on the basis of their descriptive features or symptoms.

· We need a classification system for abnormal behavior for two primary reasons.

· First, a classification system is useful to clinicians, who must match their clients' problems with the

form of intervention that is most likely to be effective.

· Second, a classification system must be used in the search for new knowledge.

Brief History of Classifying Abnormal Behavior

Brief Historical Perspective

· Currently, two diagnostic systems for mental disorders are widely recognized.

· 1--One--the Diagnostic and Statistical Manual (DSM)--is published by the American Psychiatric

Association.

· 2--The other--the International Classification of Diseases (ICD)--is published by the World Health

Organization.

· During the 1950s and 1960s, psychiatric classification systems were widely criticized. One major

criticism focused on the lack of consistency in diagnostic decisions.

· Renewed interest in the value of psychiatric classification grew steadily during the 1970s,

culminating in the publication of the third edition of the DSM in 1980.This version of the manual

represented a dramatic departure from previous systems.

The DSM-IV-TR System

· More than 200 specific diagnostic categories are described in DSM-IV-TR. These are arranged

under 18 primary headings.

· The manual lists specific criteria for each diagnostic category.

· The DSM-IV-TR employs a multiaxial classification system; that is, the person is rated on five

separate axes.

· Each axis is concerned with a different domain of information.

· Two are concerned with diagnostic categories and the other three provide for the collection of

additional relevant data.

Abnormal Psychology PSY404

DSM is not a perfect document but this imperfect document gives valuable information. Each axis of DSM

provides an important piece of information related to a person's behavior. Each axis is like a piece of a

puzzle and when all the pieces or axes are put at the right places we get a complete picture.

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