Trial of Transcranial Photobiomodulation for Depression With PET and EEG Outcomes

The system delivers 808 nm near-infrared light via fiber optics through a headset forming \~12 cm² beams at EEG sites AF3/AF4 (dorsolateral prefrontal cortex). Participants are randomized to: (1) Continuous Wave (CW, high dose) \~350 mW/cm² (\~8.4 W total); (2) Continuous Wave Low Dose (CW\_LOW) \~50 mW/cm² (\~1.2 W); (3) Pulsed Wave (PW) peak \~1050 mW/cm², 42 Hz, 33% duty cycle (avg \~350 mW/cm²); or (4) Sham device with identical cues but no light. Sessions last 429 s, 3×/week for 6 weeks (18 total). Sham matches duration/procedures. Outcomes include depressive symptoms (HAMD-17, QIDS, SDQ), FDG-PET, and EEG.