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

This study aims to investigate the potential efficacy of transcranial photobiomodulation (tPBM) as an adjunctive antidepressant treatment in patients with treatment-resistant depression (TRD), with a specific focus on the subtype predominantly presenting with somatic symptoms. tPBM is a non-invasive neuromodulation technique that utilizes near-infrared light to stimulate the prefrontal cortex. It potentially improves energy metabolism and neural function while offering advantages such as high safety and minimal side effects. Although preliminary studies support its antidepressant potential, evidence regarding the relationship between treatment parameters, stimulation frequencies, and subtype-specific efficacy remains limited. This prospective, randomized controlled trial expects to enroll 40 TRD subjects, who will be randomly assigned to either a 10 Hz or a 40 Hz group. Both groups will receive tPBM treatment twice a week for four consecutive weeks. Pre- and post-treatment clinical assessments will evaluate depressive symptoms (HDRS-17, MADRS), somatic symptoms (PHQ-15, DSSS), sleep quality, and overall functioning. Additionally, paired-pulse transcranial magnetic stimulation (TMS) will be utilized to record neurophysiological changes, specifically assessing alterations in cortical excitability and inhibition. This study expects to clarify the differences in efficacy between distinct tPBM frequencies in TRD patients, particularly those with somatic symptom-dominant subtypes. Furthermore, it aims to establish a preliminary link among tPBM treatment parameters, neurophysiological markers, and clinical symptom changes, providing a scientific basis and empirical evidence for future precision neuromodulation therapies.