Effects of Tryptophan Depletion on Brain Processing of Emotions in Patients With Mood Disorders

Study Summary

This study will investigate how the brain process emotions in healthy people and in patients who have major depression in order to better understand the causes of depression. It will examine what happens in the brain when a person responds to words related to different emotions while the brain's ability to manufacture a chemical called serotonin is reduced. Serotonin regulates functions such as emotion, anxiety and sleep, and stress hormones such as cortisol. In this study, participants' serotonin levels are reduced by depleting tryptophan, an amino acid that is the main building block for serotonin. Healthy volunteers and patients with major depression that has been in remission for at least 3 months may be eligible for this study. Candidates must be between 18 and 50 years of age and right-handed. They are interviewed about their medical and psychiatric history, current emotional state and sleep pattern, and family history of psychiatric disorders. Screening also includes psychiatric interviews and rating scales, neuropsychological tests, physical examination, electrocardiogram (EKG), and blood, urine, and saliva tests. Women have their menstrual phase determined by a blood test and home urine ovulation test kit. The study involves two clinic visits in which participants undergo tryptophan depletion and magnetic resonance imaging (MRI). Subjects arrive at the NIH Clinical Center in the morning after fasting overnight. They fill out questionnaires have a blood sample drawn, and then take 74 capsules that contain a mixture of amino acids found in the diet. At one visit they are given capsules that contain a balanced mixture of amino acids one would normally eat in a day; at the other visit, some of the capsules contain lactose instead of tryptophan, causing tryptophan depletion. At 2 p.m. participants fill out the same questionnaires they completed at the beginning of the day and have another blood sample drawn. Then they do a computerized test in the MRI scanner.