Doctor takes new findings to New Orleans neuroscience meeting. NewYork (Reuters)
Abnormally high glucose metabolism in a region at the center of the brain may cause many of the emotional symptoms associated with depression, according to a new study.
The almond-sized brain region is the amygdala, known to be important in emotional behavior and in learning the emotional significance of situations, explians Dr. Wayne Drevets, associate professor of psychiatry and radiology at the University of Pittsburgh Medical Centre, Pittsburgh, Pennsylvania.
The new findings were based on overlays of positron emission tomography (PET) scans on magnetic resonance imaging (MRI) brain scans of depressed and non-depressed individuals.
In presenting the study this week at the Society for Neuroscience Annual Meeting in New Orleans, Louisianna, Drevets said the findings may improve our understanding of how antidepressant and mood-stabilizing treatments work. They may also lead to better treatments for people with major depression and those who suffer mood changes associated with bipolar disorder (manic depression).
"In a previous study of depressed patients, we had found increased blood flow in the amygdala, and increased blood flow would go along with increased amount of communication between cells in the structure," Drevets says. "So the amygdala was overly active in depression."
In a new study, "we used a much higher resolution PET scanner and so we were able to confirm that there is, in fact, increased glucose metabolism also in this region," the researcher explains, adding that the findings were similar "in people who had bipolar illness, who were either depressed or manic." The study used PET images of glucose metabolism and MRI images of brain structure in 32 people with major depressive disorder or bipolar disorder.
"We also have a control group of 15 subjects who had neither had episodes of major depression themselves nor had family histories of depression," Drevets says.
The researcher notes the study also linked abnormal amygdala metabolism with elevated cortisol in depression - including in bipolar depressed patients.
"It's been known for about 30 years that depressed people release too much of a stress hormone called cortisol," he says.
"There's sort of a chemical cascade in the body that's responsible for releasing cortisol. That cascade is called the hypothalamic-pituitary- adrenal axis. That axis is overly active in depression, and our study is the first to suggest that the overactive amygdala might be the explanation for this effect."
Drevets explains that the amygdala helps the brain learn the emotional significance of sensory signals, such as situations that present a threat, and organizes the way those signals are expressed, from the rapid heart beat to facial expressions.