nosologies

Nosologies refer to the systems and methods for organizing diseases and health conditions. They cover naming conventions, diagnostic criteria, and hierarchical classifications used to group conditions by etiology, anatomy, clinical presentation, or prognosis. They provide standardized terms and coding schemes to support diagnosis, treatment planning, epidemiology, and research.

Historically, nosologies evolved from early symptom-based groupings to modern standardized classification schemes. The International Classification of Diseases (ICD), produced by the World Health Organization, and its revisions (ICD-10, ICD-11) are among the most widely adopted disease classification systems. In psychiatry, the Diagnostic and Statistical Manual of Mental Disorders (DSM) offers diagnostic criteria for mental disorders, while many regions use complementary or locally adapted systems. Electronic health records rely on comprehensive terminologies such as SNOMED CT to link diagnoses, findings, and procedures.

Nosology employs diverse organizing principles, including etiology, pathophysiology, and clinical phenotype, and it spans both categorical and dimensional approaches. Controversies in nosology include the reliability and validity of diagnostic boundaries, issues of comorbidity, cultural variation in symptom expression, and the balance between simplicity and descriptive accuracy.

Applications of nosology include clinical decision-making, public health surveillance, research, and health policy. Ongoing reform aims to harmonize systems across disciplines, reflect advances in genetics and neuroscience, and address challenges posed by rapidly emerging conditions and changing health needs.