What science deals with the causes, mechanisms of development, and effects of disease?

Pathology is the science that focuses on studying the causes, mechanisms of development, and effects of diseases. It encompasses a wide range of disciplines, including understanding how diseases originate (etiology), how they progress in the body (pathogenesis), and the resulting changes in tissues and organs (morphological changes). Pathologists investigate not just the biological basis of illness but also how these changes manifest clinically, making it integral to the diagnosis and understanding of diseases.

Neurology specifically deals with the nervous system and its disorders, while immunology centers on the immune system and its responses to pathogens and diseases. Physiology looks at the normal functions of living organisms and their parts, rather than focusing on disease processes. Therefore, pathology uniquely encompasses the full spectrum of disease-related study, aligning perfectly with the question's requirements.