Transcranial Photobiomodulation (tPBM) for Somatic Symptoms in Treatment-Resistant Depression

The primary objective of this study is to evaluate the clinical efficacy of moderate-dose transcranial photobiomodulation (t-PBM) at different frequencies (10 Hz and 40 Hz) in patients with treatment-resistant depression (TRD). It further aims to explore the differential efficacy across various symptom subtypes, with a particular focus on the somatic symptom-dominant subtype. Additionally, this study will collect paired-pulse neurophysiological parameters (e.g., the ratio of cortical inhibition to excitation) to preliminarily explore the neural mechanisms underlying the modulation of cortical excitability by t-PBM intervention, and to analyze their correlation with the magnitude of clinical symptom improvement. The specific aims of this study are as follows: To evaluate the differential efficacy of t-PBM at varying frequencies (10 Hz vs. 40 Hz) in improving clinical depressive symptoms (as measured by scales such as HAM-D and MADRS). To investigate the therapeutic response to t-PBM in patients with the somatic symptom-dominant depression subtype, analyzing its potential suitability for targeting specific symptoms. To explore the changes in paired-pulse TMS parameters (e.g., SICI, ICF, and LICI) before and after t-PBM treatment, gaining preliminary insights into the potential association between its cortical modulatory effects and clinical outcomes.