Objectives:
Psychosomatic disorders (somatic symptom disorder – SSD) constitute a heterogeneous group of medical conditions characterized by somatic symptoms without explained somatic causes. Due to the complexity of symptoms, they present a significant medical, social and economic challenge, and diagnosing and treating these disorders remains a substantial clinical challenge. The aim of the conducted research was an attempt to identify characteristic patterns in the surface-level brain bioelectrical activity of individuals experiencing psychosomatic disorders. The obtained results may contribute to understanding the pathomechanism of these disorders and developing objective methods for diagnosis and differentiation of functional dysfunctions.

Methods:
The study involved a group of 49 individuals: 30 patients with somatic symptom disorder (SSD) and 19 individuals in the control group. Resting-state EEG signals were recorded from the subjects under two experimental conditions (eyes open, eyes closed). The recorded signals underwent quantitative EEG (QEEG) analysis followed by statistical analysis.

Results:
EEG signal analysis revealed statistical differences between the studied groups in terms of absolute power in the Alpha band (8–12 Hz) in frontal areas (electrodes F3, Fz, F4) under eyes-open conditions, as well as in the Delta band (1–4 Hz) in the right frontal area (electrode F4) under eyes-closed conditions. Similar changes were not observed in the Beta (12–25 Hz) or High Beta (25–30 Hz) bands.

Conclusions:
The detected abnormalities in the surface-level brain bioelectrical activity may indicate potential disturbances in the reception and interpretation of visceral sensations in patients with psychosomatic disorders. The lack of differences in higher frequencies could be helpful in the differential diagnosis between these disorders and other anxiety disorders where psychosomatic symptoms are observed. The obtained results could also be useful in planning protocols involving various neurotherapeutic methods