The present invention provides a novel photobiomodulation (PBM) system and method that comprehensively directs therapeutic light energy into the brain from a combination of transcranial (through the skull) and intranasal (via the nasal channels) locations. Preferably, the present invention also provides a system and method whereby the PBM device of the present invention works in combination with a diagnostic tool to provide enhanced treatment of abnormal brain function intelligently, automatically, and unrestricted by geographical distances.