A "somatic symptom disorder" is a condition in which physical symptoms, including pain, fatigue, indigestion, or dizziness, persist without a clear cause.

These symptoms can be very disruptive to daily life, but tests to find the cause often show no abnormalities. The focus on physical symptoms is a hallmark of this disorder, so patients often seek treatment in other medical departments, such as internal medicine, neurology, anesthesiology, pain medicine, and otolaryngology, rather than mental health care.

A new study has found that somatic symptom disorder, which is characterized by physical pain but no problems at the doctor's office, is influenced by mood, and “anxiety and anger,” in particular, make patients' pain more severe.

The conclusion is based on the research conducted by Professor Park Hye-youn of the Department of Psychiatry at Seoul National University Bundang Hospital (SNUBH) and Professor Park Beom-hee of Ajou University.

The team analyzed resting-state functional MRI scans, blood tests, clinical psychological tests, neuroimmune markers in the blood, and clinical symptom scores (somatic symptoms, depression, anxiety, anger, and emotional expression disorders) in 74 patients with somatic symptom disorders and 45 healthy controls.

Somatic symptom disorder is related to the functioning of the Default Mode Network (DMN), which plays a key role in processing and regulating bodily sensations, stimuli, emotions, and stress. The DMN is an area of the brain that becomes active when a person is in a dazed state or meditation.

The researchers found that people with somatic symptom disorders had more severe physical symptoms and mood symptoms (depression/anxiety/anger) and decreased connectivity in some DMNs compared to the control group. In particular, they found that anxiety and anger had a significant effect on the functional connectivity of DMNs with somatic symptoms, meaning that when people are anxious or angry, they experience more pain, like abdominal pain and dizziness.

That seems to be because mood impairs the DMN's ability to properly recognize and process sensations, including pain, leading to distorted sensory processing that amplifies or overreacts to physical symptoms. For example, anger can increase gastric secretion and sensitivity to visceral pain, which can exacerbate functional gastrointestinal disorders or abdominal pain.

The study was the first to explore the mechanisms of physical symptoms in terms of multidimensional factors, such as brain functional connectivity and neuroimmune markers, focusing on various moods and providing scientific evidence that mood can affect physical symptoms by mediating brain function.

"The study shows that patients with somatic symptom disorder with mood symptoms, such as anxiety and anger, can alleviate their physical symptoms by effectively managing their mood symptoms," Professor Park Hye-youn said. "Since we have identified DMN as a key hub for somatic symptom disorder, we can actively try related cognitive behavioral therapy or neurostimulation therapy."

The study was funded by the National Research Foundation of Korea and published in the prestigious journal Brain, Behavior and Immunity (IF 15.1).