Traumatic brain injury (TBI) and post-traumatic stress disorder (PTSD) are common combat-related conditions that can result in impairments in cognition, including memory, attention and multi-tasking. There are few effective interventions to improve cognition in Veterans with cognitive impairment due to these conditions. Non-invasive brain stimulation techniques, like transcranial direct current stimulation (tDCS), can be used to stimulate activity in areas of the brain to optimize recovery and rehabilitation. In this study, the investigators are conducting a randomized controlled trial of tDCS to improve cognitive function in Veterans with cognitive impairment due to co-morbid TBI and PTSD. TDCS is remotely administered and paired with cognitive training.

This study is a double blinded randomized controlled trial of transcranial direct current stimulation (tDCS) to improve cognitive function in Veterans with cognitive impairment due to co-morbid traumatic brain injury (TBI) and post-traumatic stress disorder (PTSD). Eligible Veterans who choose to enroll will be randomized to active or sham stimulation with tDCS. They will undergo 10 weekdays of stimulation (active or sham) paired with cognitive training with the mobile application BrainHQ that will be conducted remotely. The Veteran and a friend/family/caregiver will be trained to perform tDCS using devices that are designed for remote use and supplied with materials necessary to conduct stimulation. A member of research staff will be on videoconferencing (i.e. HIPAA compliant VVC) with the participant to ensure proper setup of the device and be available for any questions that may arise during the session. They will undergo cognitive testing at 3 timepoints: prior to initiation of the first stimulation visit, after the last stimulation visit and 2 months after stimulation completion.

Inclusion Criteria:

• History of chronic mTBI as measured by Ohio State University Traumatic Brain Injury Identification Method
• mTBI occurred > 5 years prior to study enrollment
• History of PTSD with symptoms within the last month as confirmed PTSD Checklist (past month) score greater than or equal to 33,
• Cognitive impairment as defined by telephone Montreal Cognitive Assessment < 19
• No history of reported or documented age-related or neurodegenerative condition
• Access to internet for 1 hour per day
• Willing and able to comply with all study related procedures and capable of independently reading and understanding study materials and providing informed consent.

Exclusion Criteria:

• Skin lesions at the stimulation site that may increase conductance
• Metallic objects in the face or head (e.g. braces, fillings, implants)
• Pregnancy/lactation or planning to become pregnant during study
• History of other significant neurological disorders including seizure disorder, central nervous system tumors, stroke, cerebral aneurysm
• History of primary psychotic disorder, bipolar I disorder, active substance use disorder (moderate or greater, measured by Drug Abuse Screening Test-10)
• Active suicidal intent or plan, measured by Columbia-Suicide Severity Rating Scale
• Other conditions or circumstances that, in the opinion of investigator team, have the potential to prevent completion and/or have a confounding effect on outcome assessments.
• Unable to tolerate 2mA transcranial direct current stimulation (tDCS)

After completion of the study, de-identified and HIPAA complaint data will be shared with investigators who contact the PI and submit a formal request for access (outlining their research proposal, methods and justification for data access).

After completion of study protocol.

After completion of the study, de-identified and HIPAA complaint data will be shared with investigators who contact the PI and submit a formal request for access (outlining their research proposal, methods and justification for data access).

All study staff and participants will be blinded to study condition.