Public Release: 

How does serotonin effect depression

University Hospitals of Cleveland

CLEVELAND: Depression investigators at The Research Institute of University Hospitals of Cleveland have zeroed in on the neurotransmitter serotonin, a brain chemical that regulates emotion. Their tactics: reduce serotonin levels in each study subject to learn who is vulnerable for developing major depression.

This new study, funded by the National Institute of Mental Health, is designed to help scientists better understand the role of serotonin in people who get major depression. By examining the way people feel when serotonin is briefly reduced, UHRI investigators hope to discover new ways of predicting who is at risk for major depression and when treatment with antidepressants can safely be discontinued, according to Pedro L. Delgado, MD.

Dr. Delgado, Chairman of the Department of Psychiatry at UHC and Case Western Reserve University, is the primary investigator for this study. In the study, tests are conducted on healthy participants and upon people having previously suffered from depression. Serotonin levels are temporarily reduced for up to 8 hours and the study team then carefully monitors how the participant feels.

Both groups of study subjects will have their serotonin levels reduced through a process called "tryptophan depletion." Tryptophan, an essential amino acid, does not occur naturally in the human body but is found in certain foods. When an individual consumes those foods, his or her body uses the tryptophan to produce serotonin. Study subjects in both groups will drink a beverage that causes tryptophan depletion, thereby reducing their serotonin levels.

"It is our hypothesis that reducing serotonin in a person who is vulnerable to depression will cause depressive feeling while the same procedure in someone who is not vulnerable will have no effect," Dr. Delgado says. "We believe that the serotonin depletion procedure might be used to predict when patients no longer need medication. We also hope to identify those people who, though they never had depression, are at increased risk for it in the future."

Recent studies have shown that imbalances in serotonin levels can trigger depression. Doctors treat some patients with serotonin reuptake inhibitors (SSRI) because these medications can help to regulate serotonin levels.

"The unanswered question is: why do some people become depressed when serotonin is low while others with low serotonin levels remain depression-free?" Dr. Delgado says.

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Healthy participants in this study must be 18 to 85 years old and have no personal or family history of mental illness. People who have been previously diagnosed with major depression must be 18 to 85 years old and be currently in remission with or without antidepressant medication. Study participants will be involved with the research for 14 months. For more information, please call 216-844-2827.

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