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Press Release
Study Links Major Depression to Increased Levels of Neurons in the Brain
July 14, 2004
Temple, TX — Texas researchers have discovered that an increased number of neurons (nerve cells) in the thalamus, a part of the brain, may be responsible for major depression. Postmortem brains from patients who had been diagnosed with major depression were evaluated against brains from normal subjects and those with schizophrenia and bipolar disorder. The results, reported in the current issue of the American Journal of Psychiatry, are the first to link a psychiatric disorder with an increased number of regional neurons in the brain.
The Central Texas Veterans Health Care System, University of Texas Southwestern Medical Center and Texas A&M University System Health Science Center conducted the research.
The findings revealed that patients diagnosed with major depression had about 30-percent more nerve cells in regions of the thalamus involved with emotional regulation. In addition, the regions appeared larger in patients with major depression. The researchers also noted that a history of antidepressant use during the patient's lifetime did not appear to play a part in the neuron levels of depressed or bipolar subjects.
"Our data suggest that there may be discrete physical abnormalities in the brains of subjects with major depression, and that these changes may be responsible for the abnormal thinking patterns and the emotional impairments suffered by these patients," said principal investigator Keith A. Young, Ph.D, co-director of neuropsychiatry research at VA's health care center and associate professor of psychiatry and behavioral science at Texas A&M.
"This represents a change in the way we think about major depression, which has been considered by most scientists and physicians to be related to neurochemical imbalances, rather than being caused by abnormal brain development and structure," said Young.
The thalamus, located in the center of the brain beneath the cerebral cortex, is a major brain-processing center that acts like the central processing unit (CPU) of a computer. Emotional signals from the brain's primitive fear and aggression centers are sent to the thalamus where they are sorted out, and then sent on to the cortex where decisions are made about how to react to the signals.
"The finding of excess numbers of neurons in the thalamus in major depression is surprising because most previous work has shown that psychiatric conditions such as schizophrenia and bipolar disorder are associated with decreases, not increases, in neuron populations," said Young.
The team used sophisticated microscope imaging systems equipped with special software to carefully count the number of nerve cells in several regions of the thalamus, superimposing the thalamic tissue so that cell counts would be accurate.
Major depression is the most common mental illness. The National Alliance for the Mentally Ill estimates the disease affects about 10 million American adults (5 percent of the U.S. total). Compared to normal reaction to loss, or brief periods of sadness or low mood lasting only a few days or weeks, major depression is a recurring change in mood that can severely affect thought processes, motivation and physical health. It is the leading medical cause of disability and lost time from work, and a major factor contributing to suicide. Major depression is often treated with antidepressants, such as Prozac.
Other researchers involved in the study were Leigh A. Holcomb, Ph.D., and Paul B. Hicks, M.D., Ph.D., from VA. Holcomb and Hicks worked with a team from UT's Southwestern Medical Center department of psychiatry, led by Dwight German, Ph.D.
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Keith A. Young, Ph.D., the study's principal investigator, is available for press interviews. For telephone or on-site interviews, please contact Liz Crossan, Public Affairs Officer, VA Central Texas Health Care System, at (254) 743-2376 or elizabeth.crossan@med.va.gov. For additional assistance, please contact Jim Blue at (212) 807-3429 or james.blue@mail.va.gov.
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