Optimizing hyperbaric oxygen therapy for PTSD—The importance of dose and duration for sustained benefits

connectivity demonstrated in brain imaging following HBOT among veterans with PTSD also support this notion (8).However, for neuroplasticity to be induced and for long-lasting rather than temporary improvement of symptoms to occur, a long treatment course may be needed. Thus, while short-term response to HBOT using lower AMs may be fair, it is the long-term effect and improvement persistence that may better reflect the structural effect of the different protocols.Most of the studies in the Andrews and Harch manuscript that evaluated the effect of HBOT on PTSD assessed the short-term effects after treatment completion (Table 1). Only three of the studies also evaluated long-term effects at intervals of 6 months to 2 years. Weaver et al. (9) provided 3120 AMs and reported a 17% decrease immediately after completion of the HBOT treatment protocol, and attenuation of the improvement to 7% after 6 months and a 10% worsening of symptoms at 12 months. In contrast, in Harch et al. (10), an intensive protocol with twice-daily sessions and 3420 AMs was prescribed, reporting a 26% decrease in symptoms evaluated immediately after the treatment course completion and "further improvement" at the 6month evaluation. But Harch also reported transient worsening in some symptoms among 7 of the 30 study participants (of whom 23 had PTSD). It is not clear if the symptom worsening was occurred in the post-traumatic population.In Doenyas-Barak et al. (11), the short term improvement was 39% and the improvement persisted together with improved social and occupational function 2 years after completion of the 11,400 AMs protocol. Cifu(12) stated in their manuscript that a second evaluation of 3-month time periods following HBOT would be reported; however, no such publication could be found.To conclude, higher AMs may be necessary not just for better short-term response, but also for changes in brain activity and memory perception that may contribute to long-lasting effects. In addition, given the almost linear correlation between dose and response, the question is whether longer courses are needed to achieve even better respond.