[Classification and diagnosis: a persistent misunderstanding]

There is much debate about the limitations of the DSM classification, which is often confused with a descriptive diagnosis / case formulation.

To clarify the complementary nature of classification and diagnosis, and their advantages and disadvantages in clinical practice and in research.

We describe the distinguishing features and applications of classification and diagnosis, and the advantages and disadvantages of both. This is illustrated with three case studies of depression, bipolarity, and psychosis.

Descriptive diagnosis and classification complement each other. The former is narrative and dimensional, provides insight into the nature and development of the symptom pattern, and guides personalized treatment. It describes differences between people, in addition to psychopathological similarities. The classification emphasizes similarities between people’s behavioral patterns, is impersonal, and categorical, refers primarily to the most prominent symptom complexes, and guides more technical aspects of treatment, such as choices in pharmacotherapy. Classification is necessary for many forms of scientific research.

If classification and descriptive diagnosis are applied as they are intended, and one is aware of the limitations of both methods, they each in their own way provide guidance for treatment and research.