Trajectories of Depressive Individual Symptoms over Time during Transcranial Photobiomodulation

Transcranial photobiomodulation (t-PBM) is an innovative, non-invasive treatment for depression. This study aimed to investigate the changes in individual depressive symptoms during t-PBM treatment and identify the symptoms that improved in those who responded to treatment. The research analyzed data from two trials, the Evaluation of Light-emitting diodes Therapeutic Effect in Depression-2 and -3, focusing on patients with major depressive disorder. The patients received t-PBM treatment on the F3 and F4 regions of the scalp over eight weeks, with symptoms assessed weekly using the Quick Inventory for Depression Symptomatology (QIDS). A response was defined as a 50% or greater reduction in the QIDS score at eight weeks from baseline. Out of the 21 patients analyzed, 4 responded at eight weeks. Neurovegetative symptoms, including sleep disturbances and change in appetite, improved in ≥50% of the patients who had these symptoms at baseline. However, core depressive symptoms, including a depressed mood and lack of energy, persisted in about 80–90% of the patients. The responders showed a more than 75% improvement in these core depressive symptoms. These findings suggest that t-PBM treatment may uniquely alleviate certain neurovegetative symptoms in depression, and the improvement in core depressive symptoms might be linked to a clinical response to this treatment.