Post by MaggieNom.....
Have you heard anything about how many severe depressive episodes over
time....impacts the brain?
Here is some recent research on the subject. Now who is smarter, me or
Nom.<grin>
http://www.sciencedaily.com/releases/1999/06/990616063411.htm
Depression May Shrink Key Brain Structure
St. Louis, June 15, 1999 -- Investigators at Washington University
School of Medicine in St. Louis have found that a key brain region is
significantly smaller in people who have suffered from clinical
depression. Reporting in the June 15 issue of The Journal of
Neuroscience, they say people who have been depressed have smaller
volumes in a seahorse-shaped brain structure called the hippocampus
that is important in learning and memory.
Using three-dimensional magnetic resonance imaging (MRI), the
scientists found that otherwise healthy women with a history of
depression had smaller hippocampal volumes than those who never had
been depressed.
"In a previous, smaller study, we found a relationship between
depression and loss of volume in the hippocampus, so we anticipated
this finding," said lead author Yvette I. Sheline, M.D., assistant
professor of psychiatry, radiology and neurology. "But we also
expected to see an effect from aging. We thought the hippocampus would
be somewhat smaller in our older subjects who had never been
depressed, but instead we saw significant volume loss only in patients
with a history of depression."
The investigators scanned the brains of 48 women ranging in age from
23 to 86. Half had a history of clinical depression. The others never
had been depressed. None from either group had hypertension, diabetes,
substance abuse or other conditions linked to destruction of brain
cells. By excluding people with those conditions, Sheline expected to
see only the effects of depression and aging in the hippocampus.
Instead, there was volume loss only in those who had been depressed.
Women with a history of depression had hippocampal volumes between 9
percent and 13 percent smaller than never-depressed controls. Those
with a history of depression also scored lower on tests of verbal
memory, a process linked to hippocampal function.
Hippocampal volumes were even smaller in patients who had been
depressed more often. Although none of the subjects was clinically
depressed at the time of testing, the average woman in the study had
experienced almost five episodes of depression in her lifetime, with
one subject having lived through 18 bouts of clinical depression.
"The finding that depression can result in volume loss and that more
depression can result in even greater volume loss underscores the
importance of treating and preventing depression," Sheline said.
"Treatment not only can prevent suffering and restore quality of life.
It also appears that treating depression may limit long-term damage."
Although Sheline and colleagues found significant loss of volume in
the hippocampus, total brain volume was unchanged.
The researchers also found loss of volume in part of the amygdala, a
brain structure associated with emotion. Again, while the total volume
of the amygdala was the same, the volume in the region called the
amygdala core nucleii was smaller in those who had been depressed.
Other investigators have found that depressed patients make too much
cortisol, a stress hormone or glucocorticoid important to proper
hippocampal function. Sheline and others believe excessively high
levels of glucocorticoids may have toxic effects on the hippocampus.
But she cannot yet rule out the possibility that a person at risk for
depression may start with a smaller hippocampus.
"If I were to speculate, I would say that the fact that multiple
episodes of depression produce greater volume loss in the hippocampus
suggests that there probably is some sort of damaging effect from
depression," she said. "It also is possible that there is some other
variable - genetic perhaps - that would predispose vulnerable people
to this sort of damage. That also may be the case. But to prove it, we
would need to take MRI scans of people before they have ever had
depression."
Sheline and colleagues are beginning to re-scan some of the subjects
from this study to learn whether hippocampal volumes fluctuate over
time. They also are looking at seretonin receptors in the hippocampus
and other brain structures. The seretonin receptor on neurons is one
of the sites where antidepressant drugs are likely to work. Sheline
wants to clarify the extent to which depression contributes to a
decline in the number of seretonin receptors in the hippocampus and
other brain structures even when the number of neurons in those
regions remains the same.
###
Sheline YI et al. Depression Duration but not Age Predicts Hippocampal
Volume Loss in Medically Healthy Women with Recurrent Major
Depression. The Journal of Neuroscience, vol. 19, no. 12, pp.
5034-5043, June 15, 1999.
This work was supported by grants from the National Institute of
Mental Health.
Note: Last October, Joseph L. Price. Ph.D., professor of anatomy and
neurobiology, reported that patients with inherited depression have
fewer cells in the subgenual prefrontal cortex, a thumbnail-sized area
of the brain behind the mid-forehead.
The full-time and volunteer faculty of Washington University School of
Medicine are the physicians and surgeons of Barnes-Jewish and St.
Louis Children's hospitals. The School of Medicine is one of the
leading medical research, teaching and patient care institutions in
the nation. Through its affiliations with Barnes-Jewish and St. Louis
Children's hospitals, the School of Medicine is linked to BJC Health
System.
Be well,
HoP
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