Foundations in Classification

• Diagnostic classification

  • Assignment to categories based on shared attributes or relations

  • Classification is central to all sciences

• Idiographic strategy: what is unique about an individual’s personality, cultural background, or circumstances

• Nomothetic strategy: often used when identifying a specific psychological disorder, to make a diagnosis

• Terminology of classification systems

  • Taxonomy: classification in a scientific context

  • Nosology: taxonomy in psychological/medical phenomena

  • Nomenclature: labels in a nosological

Issues with Classifying and Diagnosing Psychological Disorders

• Categorical and dimensional approaches

  • Classical (or pure) categorical approach: strict categories

  • Dimensional approach: classification along dimensions

  • Prototypical approach: combines classical and dimensional views

• Widely used classification systems

  • Diagnostic and Statistical Manual of Mental Disorders (DSM)

    • Updated every 10-20 years

  • ICD-10

    • International Classification of Diseases

    • Published by the World Health Organization

History of the DSM

• Prior to 1980, diagnoses were made based on biological or psychoanalytic theory

• Introduction of DSM-III in 1980 revolutionized classification

  • Classification now relied on specific lists of symptoms, improving reliability and validity

  • Diagnoses classified along five “Axes” describing types of problems

• DSM-IV introduced in 1994

  • Eliminated previous distinction between psychological vs organic mental disorders

  • Reflected appreciation that all disorders are influenced by both psychological and biological factors

• DSM-IV-TR (“text revision” of DSM-IV) incorporated new research and slightly altered criteria accordingly

The DSM-5

• Basic characteristics

  • Removed axial system

  • Clear inclusion and exclusion criteria for disorders

  • Disorders are categorized under broad headings

  • Empirically-grounded, prototypic approach to classification

• Adding new diagnoses: new disorder labels are created when groups of individuals are identified whose symptoms are not adequately explained by existing labels

Unresolved Issues in DSM-5

• The problem of comorbidity

  • Comorbidity: 2 or more disorders for the same person

  • High comorbidity is extremely common

  • Emphasizes reliability, maybe at the expense of validity

• Dimensional classification

  • DSM was intended to move toward a more dimensional approach, but critics say it doesn’t improve much from DSM-V

• Labeling issues and stigmatization

  • Some labels have negative connotations and may make patients less likely to seek treatment