Ketamine Treatment for PTSD and MDD in TBI

The goal of this clinical trial is to examine the use of sedative ketamine to treat depression and post-traumatic stress disorder (PTSD) in Veterans with mild to moderate traumatic brain injury (TBI). The main questions it aims to answer are: * Efficacy of ketamine to reduce symptoms of depression and/or PTSD * Safety of ketamine to treat depression and/or PTSD in TBI Participants will be randomly assigned to receive either ketamine or midazolam (active placebo) twice a week for 3 weeks. During participation, subjects will be interviewed, have lab tests, and complete rating scales, and questionnaires.