Major depressive disorder (MDD) and social anxiety disorder (SAD) are two of the most debilitating mental disorders affecting millions of people across the globe. People with MDD or SAD often find difficulty in completing everyday tasks, and maintaining social and personal relationships. An overlap in the clinical symptoms between the two disorders often points to similar brain mechanisms. Very few studies have directly compared the brain structures of people afflicted with these illnesses. A recent study by Sichuan University in Chengdu, China, found that there is a common pattern of structural abnormalities in brains of people suffering from depression and social anxiety.
For the study, lead author Youjin Zhao M.D., Ph.D. from the Sichuan University along with co-author Su Lui, M.D., used high-resolution MRI scans to examine alterations between the brain’s gray matter among SAD and MDD patients. They examined high-resolution images from 24 SAD and 37 MDD patients, and 41 healthy controls (HC). Their focus was on the thickness of the cortex, the outer layer of the cerebrum, which is the principal part of the brain. According to the authors, the differences between the patients of SAD and MDD and healthy controls were related to either the thickening or thinning of the cortex.
Impact of cortical thickening and thinning
The authors discovered that as compared to healthy controls, both MDD and SAD patients showed cortical thickening in the insular cortex. This region is associated with self-awareness and perception. According to Zhao, the thickening may be a result of inflammation or continuous coping efforts and emotional regulation attempts of SAD and MDD patients.
In regards to cortical thinning, Zhao remarked that other research provides evidence that a reduced cortical thickness in some brain regions may result in the decreased thickness of the frontal lobe, responsible for emotion regulation.
Brain differences among MDD and SAD patients
The authors also found differences in the brains of people with MDD and SAD. Those suffering from MDD showed alterations in brain regions associated with emotional, cognitive, and behavioral and social functioning whereas brains of those suffering from SAD had a disorder-specific involvement in regions associated with handling fear. Though the differences were apparent, the exact relationship between the two disorders and cortical thickening of the brain are still to be understood.
According to Zhao, “Our findings provide preliminary evidence of common and specific gray matter changes in MDD and SAD patients. Future studies with larger sample sizes combined with machine learning analysis may further aid the diagnostic and prognostic value of structural MRI.”
Anxiety disorders are characterized by extreme fear or worry leading to avoidance of situations and people that might trigger or worsen the symptoms. This can have a negative impact on one’s personal and professional life. In the United States alone, anxiety disorders affect nearly 18 percent of the adult population every year. A person suffering from MDD can be bogged down by an overwhelming feeling of sadness and often harbor suicidal thoughts. Both anxiety and depression-related problems are treatable using an integrated approach involving medication, behavioral therapies and family intervention.