Stress is often described as a feeling of being overwhelmed, worried or run-down. Stress can affect people of all ages, genders and circumstances and can lead to serious physical and psychological health issues. By definition, stress is any uncomfortable "emotional experience accompanied by predictable biochemical, physiological and behavioral changes. Chronic stress may lead to anxiety, depression, digestive problems, headaches, heart disease, sleep problems, weight gain, memory and concentration impairment. High levels of stress may adversely affect the immune, cardiovascular, neuroendocrine and central nervous systems. In addition, an extreme amount of stress can take a severe emotional toll. While people can overcome minor episodes of stress by tapping into their body's natural defenses to adapt to changing situations, excessive chronic stress, which persists over an extended period of time, can be psychologically and physically disabling. Chronic stress affects the whole body. It can have several physical or psychological symptoms, which can make functioning on a daily basis more challenging.