Light Therapy to Improve Sleep in TBI: Sleep-active Biomarkers and Glymphatic Function

All subjects must: 1. Male and female; any race; 18-89 years of age. 2. Be English speaking.\* 3. Be accessible via phone. 4. Be non-decisionally impaired. Determined by assessing the subject's ability to verbalize their understanding of the protocol back to us during the informed consent process. 5. Not have a history of macular degeneration. 6. Not have a history of bipolar disorder. 7. Not be currently using a lightbox or a negative ion generator. 8. Not be a shift worker. 9. Have a documented history of TBI via the Head Trauma Events Characteristics (HTEC) or OHIO conducted in accordance with VA/DoD Clinical Practice Guidelines.88 10. Present with self-reported sleep-wake disturbances. 11. Remain clinically stable for current pharmacologic treatment related to depression/anxiety, sleep, and pain. 12. MRI specific compatibility requirements: * No pacemaker, wires, defribrillator or implanted heart valves * No history of head surgery requiring aneurysm clips * No history of other orthopedic or general surgery requiring the implantation of ferrous pins, joints, electric devices/pumps, or other foreign metal objects * History of eye exposure to metal (unprotected welding/metalworking/shrapnel) is allowable provided the participant screens negative for metal in the eyes on an orbital x-ray or is able to provide clinical documentation of having screened negative. * No history of non-removable hearing aids, middle/inner ear prosthesis, or dentures * No history of claustrophobia; if unsure participant will be pre-screened in our mock scanner * Not currently pregnant, breastfeeding, or have an implanted IUD. Participants who are unsure of their pregnancy status will be administered an hCG urine pregnancy test the day of their scan. * Able to lay flat on their back comfortably without a thick pillow for an extended period of time. * Shoulder width does not exceed width for safety fitting in the MRI bore. * This study is limited to English-speaking participants because all assessments, interventions, and consent materials are currently validated and approved only in English. Expanding to other languages would require translation and psychometric validation, which are beyond the scope and budget of this study. This limitation is acknowledged and will be addressed in future research as resources permit. Finally, the study team is only fluent in English, making it infeasible to accurately consent or interact with non-English speakers without interpreting services which again is outside of the scope of this projects budget and timeline. Proceeding without formal translation services would risk miscommunication in informed consent, data collection, or participant support and thus protects participants informed consent and participant understanding.