Psychiatric diagnosis rests on necessary conditions plus m-of-n symptom counts.

Evidence

The DSM, along with other disease classification systems (e.g., the WHO’s “International classification of diseases,” https://icd.who.int/en) illustrates how typological thinking dominates theory and practice in the mental health area. There are many imperatives (e.g., medical insurance) to classify a person’s disorder clearly into one type. The DSM is a nice example because I have found no justification of the methodological logic used to construct disorders. In general the DSM uses the m-of-n rule along with some necessary conditions. Thus, most disorders constitute what this book calls hybrid concepts. — Gary Goertz, Social Science Concepts and Measurement, 1200

Categorization

• XREF: Extends the reader’s archival/categorical-thinking thread: the DSM as a state-adjacent taxonomy whose construction logic is never justified, parallel to colonial racial classification.
• SHARE: Worth sending to anyone working in mental health or clinical research who assumes DSM categories were methodologically derived rather than assembled from m-of-n rules.