Which branch of medicine explicitly focuses on mental illness prevention and treatment?

Psychiatry is the branch of medicine that specifically focuses on the prevention, diagnosis, treatment, and study of mental disorders, including emotional and behavioral issues. Psychiatric practice encompasses a range of approaches, including therapy, medication management, and various psychological interventions aimed at improving patients' mental well-being.

This discipline is distinct from the other branches listed, which primarily address different aspects of health care. For instance, pediatrics focuses on the health of infants, children, and adolescents, emphasizing physical growth and development, as well as preventive health measures for young patients. Internal medicine concentrates on the prevention, diagnosis, and treatment of adult diseases, particularly those related to chronic conditions and internal organ systems. Family medicine takes a broad approach, treating patients of all ages, but the primary focus is on overall health care and family dynamics rather than specifically targeting mental health.

By addressing mental illness with specialized knowledge and treatment methods, psychiatry plays a crucial role in managing and understanding the complexities of mental health, making it the correct choice for this question.