الفهرس 
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Abstract
Classification is the process by which the complexity of phenomena is reduced by arranging them into categories according to some established criteria for one or more purposes (Jablensky and Kendell, 2002).
The DSM-IV is a categorical classification system. The categories are prototypes, and a patient with a close approximation to the prototype is said to have that disorder. For nearly half the disorders, symptoms must be sufficient to cause clinically significant distress or impairment in social, occupational, or other important areas of functioning (Maser and Patterson, 2002).
The most fundamental scientific criticism of the DSM concerns the validity and reliability of its diagnoses. This refers, roughly, to whether the disorders it defines are actually real conditions in people in the real world, that can be consistently identified by its criteria. These are long-standing criticisms of the DSM, and continuing despite some improved reliability since the introduction of more specific rule-based criteria for each condition (Dalal and Sivakumar, 2009).
DSM–V research planning work groups were formed to develop white papers that would guide research in a direction that would maximize impact on future editions of the diagnostic manual. The nomenclature work group, charged with addressing fundamental assumptions of the diagnostic system, concluded that it will be “important that consideration be given to advantages and disadvantages of basing part or all of DSM–V on dimensions rather than categories” (Rounsaville et al., 2002).
A categorical (binary) diagnosis is a yes/no answer to ‘‘Does this patient have the disorder?’’ A dimensional diagnosis is an ordinal response describing the patient’s status. While there has long been argument about categorical versus dimensional diagnosis, it is important to realize that whenever there is one, there is also the other (Kraemer et al., 2004).
The general feeling was that in DSM-V, both categorical and dimensional diagnoses will be needed and these should well coordinate with each other. The overriding statistical issues then are how to demonstrate high reliability and validity of whatever proposed diagnoses are to be included (Kraemer et al., 2007).