A fairly recent study looked at whether red light therapy (using a helmet and also intranasal red light from Vielight) might improve cognitive function in people with chronic, mild traumatic brain injury. The results suggest that it does. According to the study, "Participants and family reported better ability to perform social, interpersonal, and occupational functions."
Naeser Margaret A., Zafonte Ross, Krengel Maxine H., Martin Paula I., Frazier Judith, Hamblin Michael R., Knight Jeffrey A., Meehan William P. III, and Baker Errol H.. Journal of Neurotrauma. June 1, 2014, 31(11): 1008-1017. doi:10.1089/neu.2013.3244.