What is stress? Stress is mental or physical strain due to threats, danger, life changes, and everyday challenges. Stress typically brings on the fight-or-flight response, which prepares your body for an emergency. As part of this response, your adrenal glands increase secretion of substances, such as cortisol, epinephrine and norepinephrine. This raises your heart rate and blood pressure; constricts the veins of your skin; dilates your pupils, the airways of your lungs, and the blood vessels of your heart; decreases the activity of your digestive and immune systems; increases your alertness; and increases the availability of blood glucose, which your body can quickly convert to energy. Short-term activation of the fight-or-flight response can be very helpful in dealing with brief periods of stress. Once the stress has passed, adrenal secretion of these hormones returns to normal. Excessive or chronic stress, however, can lead to prolonged exposure to the substances released as part of the fight-or-flight response, which can lead to heart disease, diabetes, and other complications. Prolonged stress can cause psychological and cognitive symptoms, such as anxiety, depression, agitation, poor concentration, forgetfulness, and sleep disorders. It can also cause physical symptoms, such as headache, muscle and body aches, digestive problems, weight changes, fatigue, shortness of breath, and chest pain. While stress is not an illness, it can cause significant health problems; therefore, managing your stress is recommended. This may involve developing coping skills, avoiding stressful situations, and making healthy lifestyle changes. Chronic stress can lead to serious, even life-threatening complications. Seek immediate medical care (call 911) for chest pain or pressure, rapid heart rate (tachycardia), difficulty breathing, heavy sweating, severe anxiety, dizziness or lightheadedness, confusion, change in level of consciousness or alertness, severe pain, severe nausea with or without vomiting, weak pulse, seizure, or sudden change in vision, or if you think you are a danger to yourself or others, including threatening, irrational or suicidal behavior. If you have symptoms associated with stress or your stress is persistent or causes you concern, seek prompt medical care.