Researchers at UCLA suggest a possible root of depression in people with
multiple sclerosis (MS) that is not psychological, bust physical. They trace
the cause to atrophy of a specific region of the hippocampus, a critical part
of the brain involved in mood and memory, according to a press release.
Senior study author Nancy Sicotte, MD a UCLA associate professor of
neurology, Stefan Gold, lead author and a postdoctoral fellow in the UCLA MS
Program, and colleagues used high-resolution magnetic resonance imaging to
identify three key sub-regions of the hippocampus that were found to be smaller
in people with MS when compared with the brains of healthy individuals.
“Depression is one of the most common symptoms in patients with
MS,” Gold stated in the release. “It impacts cognitive function,
quality of life, work performance and treatment compliance. Worst of all, it’s
also one of the strongest predictors of suicide.”
The researchers also found a relationship between this atrophy and
hyperactivity of the hypothalamic-pituitary-adrenal (HPA) axis. The HPA axis is
part of a system that controls reactions to stress and regulates many
physiological processes.
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The researchers examined three sub-regions of the hippocampus region
CA1, CA3 and the dentate gyrus area of the hippocampal region called CA23DG.
They imaged 29 patients with relapsing remitting MS and compared them with 20
healthy control subjects who did not have MS. They also measured participants’
cortisol level three times a day; cortisol is a major stress hormone produced
by the HPA axis that affects many tissues in the body, including the brain.
In addition to the difference between MS patients and healthy controls,
the researchers found that the MS patients diagnosed with depression showed a
smaller CA23DG sub-region of the hippocampus, along with excessive release of
cortisol from the HPA axis.
“This idea of a link between excessive activity of the HPA axis and
reduced brain volume in the hippocampus hasn’t received a lot of
attention, despite the fact that the most consistently reproduced findings in
psychiatric patients with depression (but without MS) include hyperactivity of
the HPA axis and smaller volumes of the hippocampus,” Sicotte stated.
“So the next step is to compare MS patients with depression to psychiatric
patients with depression to see how the disease progresses in each.”
