Effects of Bright Light Therapy in Mild Traumatic Brain Injury

Inclusion Criteria: * Age range between 18 and 50. * Subjects must be right handed. * The primary language of the subjects must be English. * Subjects have experienced a "concussion" or mTBI within the preceding 18 months, but no sooner that 4 weeks prior to their screening. The occurrence of a concussion or mTBI must be documented by a medical report or other professional witness documentation. * If documented, Glasgow Coma Scale in the range of 13-15 following the injury. * Subjects must have complaints of sleep difficulties that emerged or worsened following the most recent head injury. * At least half of subjects must have evidence of sleep onset insomnia or delayed sleep phase disorder. Exclusion Criteria: * Any other history of neurological illness, current Diagnostic and Statistical Manual (DSM-IV) Axis I disorder, lifetime history of psychotic disorder, or head injury with loss of consciousness \> 30 minutes * Complicating medical conditions that may influence the outcome of neuropsychological assessment or functional imaging (e.g., HIV, brain tumor, etc.) * Mixed or left-handedness * Abnormal visual acuity that is not corrected by contact lenses * Contraindicated conditions noted by the manufacture of the light device such as the use of photosynthesizing medications, history of cataract surgery, and pre-existing eye conditions. * Metal within the body, claustrophobia, or other contraindications for neuroimaging * Less than 9th grade education * Excess current alcohol use (more than 2 instances of intake of 5+ drinks (men) when or 4+ drinks (women) when drinking in the past two months, and/or on average drinking \> 2 drinks per day (men); \> 1 drinks per day (women) during the past two months * History of alcoholism or substance use disorder * Significant use of illicit drugs * History of marijuana use within the past 6 weeks, use of marijuana before the age of 16, and/or use of \> 20 marijuana cigarettes throughout the participant's lifetime. * Subjects who engage in shift-work, night work, or who have substantially desynchronized work-sleep schedules (i.e., sleeping later than 10:00 a.m. more than once a week) will be excluded