Fatigue in Healthy Individuals

Study Summary

Background: * People with many different diseases have symptoms of fatigue, which is a general sense of tiredness; however, the causes are not fully understood. Fatigue symptoms may be related to a person s level of fitness, health, and blood chemistries. * Researchers are studying the potential role of plasma cytokines (signaling molecules) and hypothalamic-pituitary-adrenal (HPA) axis (part of the neuroendocrine system that controls stress) functioning in symptoms of fatigue. Objectives: * To characterize the symptoms of fatigue in healthy individuals. * To collect information on fatigue, pain, depression, stress, sleepiness, and quality of life from healthy adults of all ages. * To compare results obtained from people with various illnesses to better understand possible causes of fatigue that are associated with those diseases. Eligibility: * Physically and mentally healthy volunteers18 years of age or older who can speak and read the English language. * Exclusion criteria include individuals with a disease or condition causing significant fatigue (congestive heart failure, cancer, or sleep disorders), individuals taking medicines that cause fatigue (beta blockers, diuretics, or narcotics), and individuals who have a major psychiatric condition (major depression, anxiety disorder, or schizophrenia). * The following individuals may not participate: those who have two more alcoholic drinks per day, who use illicit drugs, or who drink more than 4 cups of coffee, 8 cups of soda or tea, or similar amounts of other caffeine-containing beverages a day, or eat more than 1 pound of chocolate per day; and individuals who worked evenings or night shifts in the past month. * Women who are pregnant or breastfeeding are not eligible. Design: * Participants must make two outpatient visits to the Clinical Center. Each visit will last 5 hours and participants must refrain from smoking and consuming alcohol and caffeine for at least 24 hours. * During the first study visit,