Researchers said that atrophy of a specific region of the hippocampus, a critical part of the brain involved in mood and memory, leads to depression among MS patients.
In the first such study in living humans, senior study author Dr. Nancy Sicotte, Stefan Gold, 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.
The researchers also found a relationship between this atrophy and hyperactivity of the hypothalamic-pituitary-adrenal (HPA) axis, a complex set of interactions among three glands.
The HPA axis is part of the neuroendocrine system that controls reactions to stress and regulates many physiological processes.
It is believed that this dysregulation may play a role in the atrophy of the hippocampus and the development of depression.
"Depression is one of the most common symptoms in patients with multiple sclerosis. 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," said Gold.
The researchers examined three sub-regions of the hippocampus region- CA1, CA3 and the dentate gyrus area of the hippocampal region called CA23DG (CA stands for cornu ammonis).