A neuroimaging study conducted in South Korea has revealed that individuals diagnosed with social anxiety disorder exhibit an increased cortical thickness in several brain regions when compared to individuals without the disorder. Through whole-brain analysis, the study also discovered a reduction in the number of neurons within areas associated with attention and socio-emotional processing in those with the disorder. The findings were published in the journal Psychiatry Research: Neuroimaging.
Social anxiety disorder is a chronic mental health condition characterized by an intense fear of social situations where one may be judged, embarrassed, or rejected. People with this disorder often experience excessive self-consciousness, anxiety, and avoidance of social interactions. This can significantly impair their daily functioning and quality of life. Symptoms of social anxiety include a rapid heartbeat, sweating, and trembling in social situations, and an overwhelming urge to flee from them.
Social anxiety disorder is one of the most common mental disorders, often occurring together with depression. It attracts a lot of research interest, much of which focuses on neural underpinnings of the disorder. So far, neuroimaging studies identified various brain areas whose functioning seems to be disrupted in individuals with this disorder.
A recent study on mice even linked social anxiety to the activity of specific proteins created through the work of the immune system demonstrating that they can cause symptoms similar to social anxiety by altering distances between neurons in one specific region of the brain (nucleus acumbens).
Study author Dasom Lee and her colleagues wanted to better explore the alterations in brain structure that might be attributable to social anxiety disorder. They were interested in observing any thickening or thinning of the cerebral cortex, the outer layer of the brain. These areas are thought to be involved in higher cognitive functions like thinking, memory, and decision-making. Their thickening and thinning are a part of the brain’s natural ability to adapt and change in response to activity and environmental factors. This ability of the brain is called neuroplasticity.
The study included 36 patients with social anxiety disorder, recruited from the psychiatric outpatient clinic at Seoul National University Hospital and through community advertisements, and 42 healthy individuals. Nearly half of the participants in both groups were male, with an average age of 25 years.
The study authors screened candidates with social anxiety disorder using a battery of assessments and included only those with sufficiently severe symptoms. After inclusion in the study and assignment to groups, all participants underwent functional magnetic resonance imaging of their brains.
Results showed that individuals with social anxiety disorder tended to have significantly increased cortical thickness in the insula, the superior parietal lobule, the frontopolar cortex, and the superior temporal gyrus regions of the brain compared to healthy participants.
The insula is involved in processing emotions, bodily sensations, and autonomic functions, while the superior parietal lobule plays a role in spatial orientation, attention, and the integration of sensory information. The frontopolar cortex is associated with complex cognitive functions, including decision-making, problem-solving, and integrating information from different brain regions. Meanwhile, the superior temporal gyrus is involved in processing auditory information, language comprehension, and social cognition.
On the other hand, participants with social anxiety disorder tended to have reduced thickness in the left superior/middle frontal gyrus and left fusiform gyrus regions. The left superior/middle frontal gyrus is involved in higher cognitive functions such as decision-making, attention, and working memory, while the left fusiform gyrus plays a crucial role in visual recognition, particularly in processing faces and written words.
The magnitude of these changes was not associated with the severity of social anxiety symptoms.
“In summary, this study provided the evidence of structural alterations in brain areas consistently linked to functional abnormalities in SAD [social anxiety disorder]. Specifically, we identified altered brain structures in frontal (frontopolar, SFG/MFG) [superior/middle frontal gyrus], temporal (STG, fusiform), parietal (SPL) cortical regions as well as in (para)limbic region (insula),” the study authors concluded.
“These regions are convergent with prior functional alterations of salience and frontoparietal networks for attentional functions, and autobiographical and social structures for socially emotional processing in patients with SAD. The convergence of functional and structural evidence indicates that SAD has distinct underlying neural mechanisms.
The study sheds light on the alterations in brain structure of individuals with social anxiety disorder. However, it also has limitations that need to be taken into account. Most notably, the presented results came from whole-brain analysis. Results of region-of-interest analysis, which is a technique that focuses on specific brain regions to study their structure, function, or connectivity in detail, did not align with them. This means that these findings may not be consistent across different analytical approaches and that further investigation is needed to verify them.
The paper, “Alterations in cortical thickness of frontoparietal regions in patients with social anxiety disorder,” was authored by Dasom Lee, Ye-Ha Jung, Suhyun Kim, Yoonji Irene Lee, Jeonghun Ku, Uicheul Yoon, and Soo-Hee Choi.