Both fear and anxiety send signals through the body that prepare all systems for possible danger. Hormones, such as adrenaline and catecholamine, are released in what is known as the "fight or flight" response. The sudden increase in hormone levels speeds up the heart and increases the amount of blood being pumped. At the same time, the muscles tighten, increasing the individual's ability to fight or flee from danger. The intensity of these physiological responses varies according to the seriousness of the event or thought that sparked the emotion, the strength of the individual's fear or anxiety, and his or her previous experience and genetic makeup. Thousands of scientific studies over the past several years show that high blood pressure, ulcers, migraine headaches, strokes, alcoholism, depression, anger, fatigue, drug addiction and many other medical conditions are often due to the long-term effects of stress. Depressed people will seem sad, or "down," or may be unable to enjoy their normal activities. They may have no appetite and lose weight (although some people eat more and gain weight when depressed). They may sleep too much or too little, have difficulty going to sleep, sleep restlessly, or awaken very early in the morning. They may speak of feeling guilty, worthless, or hopeless; they may lack energy or be jumpy and agitated. They may think about killing themselves and may even make a suicide attempt. Some depressed people have delusions (false, fixed ideas) about poverty, sickness, or sinfulness that are related to their depression. Often feelings of depression are worse at a particular time of day, for instance, every morning or every evening. Using brain imaging technologies and neurochemical techniques, scientists are finding that a network of interacting structures is responsible for these emotions. Much research centers on the amygdala, an almond-shaped structure deep within the brain. The amygdala is believed to serve as a communications hub between the parts of the brain that process incoming sensory signals and the parts that interpret them. It can signal that a threat is present, and trigger a fear response or anxiety. It appears that emotional memories stored in the central part of the amygdala may play a role in disorders involving very distinct fears, like phobias, while different parts may be involved in other forms of anxiety. Psychoanalytic theory holds that anxiety stems from unconscious conflict arising from discomfort or distress during childhood. Once the source of the anxiety is identified, it can be eliminated by resolving the underlying conflict. However, most studies find that people with anxiety disorders come from stable homes, with childhood backgrounds similar to those of people without anxiety disorders.
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