Behavioral science is a broad field that encompasses various disciplines such as psychology, sociology, anthropology, and economics. Within this field, health psychology is a specific branch that focuses on the relationship between psychological factors and physical health. Health psychology considers how individual behaviors and lifestyles affect a person's overall health, including the prevention and treatment of disease, identification of health risk factors, improvement of the healthcare system, and the application of psychological principles to physical health.The traditional biomedical model of health defines it as the absence of disease. However, this view has limitations when it comes to chronic illnesses, which are now leading causes of death. A more comprehensive understanding of health considers it a state, not just the absence of disease. This means that factors such as unhealthy habits, poor social support, stress, and avoiding medical care can increase the risk of disease.There are various dimensions to the concept of illness, including not feeling normal, specific symptoms, specific illnesses, consequences of illness, and the absence of health. Psychology has a significant relevance to health, as emotions can lead to physiological changes, personality traits may relate to specific diseases, and emotional conflicts can be precursors to some diseases. Some illnesses are even labeled as "psychosomatic," including peptic ulcer, rheumatoid arthritis, ulcerative colitis, hypertension, asthma, hyperthyroidism, and others.In summary, behavioral science encompasses various disciplines that study human behavior, including psychology, sociology, anthropology, and economics. Health psychology is a specific branch that examines the relationship between psychological factors and physical health, including the prevention and treatment of disease, identification of health risk factors, improvement of the healthcare system, and the application of psychological principles to physical health.