Health psychology is the study of psychological and behavioral processes in health, illness and healthcare. It is concerned with understanding how psychological, behavioral and cultural factors contribute to physical health and illness. Psychological factors can affect health directly. For example, chronically occurring environmental stressors affecting the hypothalamic–pituitary–adrenal axis, cumulatively can harm health. Behavioral factors can also affect a person's health. For example, certain behaviors can over time, harm or enhance health.