HBOT was found to be safe and significantly effective for veterans with mild to moderate TBI PPCS with PTSD in all four outcome domains: clinical medicine, neuropsychology, psychology, and SPECT imaging.. . . . The major findings in this study were: 1) the significant improvements and magnitude of improvements in all outcome instruments (symptoms, cognition, mood, quality of life, and imaging) that were reproducible (strengthened P values) from the first 16 subjects27 to the final 14 subjects, 2) the abnormal brain blood flow pattern that became nearly indistinguishable from Controls after treatment, 3) one of the longest follow-up periods of any HBOT/PPCS study, 4) the increased symptom improvement six months post treatment, and 5) the reduction in suicidal ideation. Effect sizes and confidence intervals were substantial. These findings were mirrored by a reciprocal reduction or elimination of psychoactive and narcotic prescription medication usage, and maintained abstinence from the same medication discontinued immediately pre-HBOT.