In psychology, stress is a feeling of strain and pressure. Physiological or biological stress is an organism's response to a stressor such as external or internal condition or situation. Stress is the body's method of reacting to a challenge.
Excessive amounts of stress may lead to bodily harm. Stress can increase the risk of strokes, heart attacks, ulcers and mental illnesses such as depression. Permanent stress may lead to many chronic illnesses. Stress can alter memory functions, immune function, metabolism and susceptibility to diseases.