Ætiologi

Ætiologi, or etiology, is the study of the origins and causes of diseases and other health-related phenomena. It seeks to identify the factors that give rise to a condition, the mechanisms by which these factors act, and the temporal sequence from exposure to outcome.

Etymology: the term derives from Greek aition, meaning cause, and logos, meaning study. In medical and scientific use, ætiologi describes the investigation of why and how diseases develop.

Scope and classification: etiologies are diverse. Infectious etiologies are caused by pathogens such as bacteria, viruses, or fungi. Genetic etiologies arise from inherited or de novo mutations. Acquired etiologies result from environmental exposures, lifestyle factors, or immune, metabolic, or other bodily processes. Congenital etiologies are present at birth. Multifactorial etiologies involve multiple interacting factors, while iatrogenic etiologies are caused by medical interventions or treatments.

Methods: determining etiology relies on clinical evaluation, patient history, and physical examination, complemented by laboratory tests, imaging, and sometimes genetic analysis. Epidemiological and experimental data support causal inferences. Classic criteria for causality include Koch’s postulates and Hill’s criteria, though modern understanding recognizes complexity, confounding, and the difference between association and causation.

Clinical relevance: understanding the etiological basis of a disease guides treatment choices, informs prevention and public health measures, and shapes research priorities. In many conditions, the exact cause remains unknown or multifactorial, underscoring the ongoing need for rigorous investigation in ætiologi.