Researchers using MRI have discovered a common pattern of structural abnormalities in the brains of people with depression and social anxiety, according to a study presented at the annual meeting of the Radiological Society of North America (RSNA), which took place from November 26 to December 1 in Chicago.
Major depressive disorder (MDD), or depression, and social anxiety disorder (SAD) share some clinical symptoms, suggesting the two disorders may have similar brain mechanisms. However, few studies have directly compared the brain structural effects of the two disorders, says the author of the new study, Youjin Zhao MD, PhD, from Sichuan University in China.
Zhao and co-author Su Lui, MD, used MRI to assess alterations in the brain’s gray matter among MDD and SAD patients. They focused on the thickness of the cortex, which is the outer layer of the cerebrum, or principal part of the brain.
The researchers acquired and analyzed high-resolution images from 37 MDD patients, 24 SAD patients and 41 healthy control individuals. Both MDD and SAD patients, relative to healthy controls, showed gray matter abnormalities in the brain’s salience and dorsal attention networks. The salience network is a collection of brain regions that determine which stimuli are deserving of our attention, while the dorsal attention network plays an important role in focus and attentiveness.
“Our findings provide preliminary evidence of common and specific gray matter changes in MDD and SAD patients,” Zhao says. “Future studies with larger sample sizes combined with machine learning analysis may further aid the diagnostic and prognostic value of structural MRI.”
The differences between the MDD and SAD patients and the healthy controls related to either thickening or thinning of the cortex. For instance, both MDD and SAD patients, relative to healthy controls, showed cortical thickening in the insular cortex, a brain region vital to perception and self-awareness.
It is still unclear exactly what the relationship is between the clinical manifestations of MDD and SAD and cortical thickening in brain regions like the anterior cingulate cortex, a part of the brain associated with emotion, Zhao says.
As for cortical thinning, Zhao says that other research provides convincing evidence to support the theory that reduced cortical layer thickness in some brain regions may result in the decreased thickness of the frontal lobe, a large part of the brain that is involved in variety of functions, including emotion.
The researchers also found disorder-specific involvement of the brain’s “fear circuitry” in patients with SAD and involvement of the visual recognition network in patients with MDD. Alterations in the brain within the region of the visual recognition network might be related to impaired selective attention and working memory in MDD, Zhao indicates.
“The visual recognition network is involved in emotional facial processing, which is crucial for social functioning,” she says. “Depression has been associated with structural alterations in these regions.”
