This article is part of the HBOT Radar series, where we summarize the latest published hyperbaric oxygen therapy research.
Disclaimer: This article is intended for educational and informational purposes only. It summarizes published medical research conducted in clinical settings and does not evaluate Brain Spa Hyperbaric products. The hyperbaric chambers offered on this website are non-medical wellness devices and are not intended to diagnose, treat, cure, or prevent any disease. Do not make medical decisions based on this article — consult a qualified healthcare professional.
Title:
Randomized controlled trial shows PTSD patients need at least 35% symptom improvement during HBOT to achieve long-term gains
What this study examined
This 2025 analysis re-evaluated data from a randomized controlled trial of 56 male veterans with treatment-resistant PTSD, comparing:
- Hyperbaric oxygen therapy (HBOT)
vs - Sham treatment
The goal was to understand whether HBOT has a “threshold effect” — meaning:
If patients improve enough during the protocol, their improvements continue growing after treatment ends. If they do not reach that threshold, the benefits may fade.
This is the first PTSD study to formally test this idea.
HBOT protocol used in the RCT
- 2.0 ATA
- 100% oxygen
- Standard neuroplasticity protocol (40+ sessions)
- Compared to sham
This protocol has been used widely in brain injury and neurological HBOT research.
This trial was conducted in a clinical research setting under medical supervision. Results from clinical research cannot be directly applied to other settings or devices — always consult a healthcare professional.
What kind of analysis this is. The original trial was randomised and sham-controlled. This paper is a re-analysis of its data, dividing participants after the fact according to how much they improved. That design cannot establish cause. People who respond well to a treatment tend to keep doing well for reasons that have nothing to do with the treatment — they may have been less severe, better supported, or simply on a different trajectory from the start. The paper also does not report whether the same threshold pattern appeared in the sham group, which would be the obvious check.
Key findings
1. A clear threshold exists: ≥ 35% improvement
Participants who achieved 35% or more reduction in PTSD symptoms by the end of treatment:
- continued improving over the next 3 months
- maintained gains
- in many cases improved even more after HBOT ended
Participants who improved less than 35% tended to slide backward over time.
The 35% figure was found by looking at these same 56 patients, not by testing a threshold decided in advance. Until it is checked in an independent group, it is a pattern in one dataset rather than a target.
2. Intrusive symptoms (flashbacks, nightmares) showed the strongest improvement
Changes in Cluster B symptoms had the strongest correlation with overall recovery:
- r = 0.74 at end of treatment
- r = 0.80 at 3-month follow-up
This means improvements in intrusive symptoms were tightly linked to total PTSD improvement.
3. Avoidance symptoms best predicted long-term success
Improvement in Cluster C symptoms (avoidance behaviors) during HBOT:
- strongly predicted continued recovery
- helped determine who would maintain improvements after HBOT
This is clinically important because avoidance often blocks trauma processing; reducing it early may open the door to long-term healing.
4. The biology supports a threshold model
The authors propose that HBOT’s effects on brain neuroplasticity likely involve “bistable circuit dynamics” — simplified meaning:
- once neural circuits shift into a healthier state, they tend to stay there
- but the shift only happens if improvement crosses a specific biological threshold
The bistable-circuit explanation is the authors' proposal for why a threshold might exist. The analysis does not test it.
Why this matters
What this analysis suggests, with the caveats above:
- PTSD improvements are not linear — they depend on crossing a biological tipping point
- the authors propose that neural circuits may settle into a more stable state once a certain degree of improvement is reached
- the 35% figure gives future trials something specific to test
- improvements continue after treatment if the threshold is reached
Treatment-resistant PTSD is a population with few remaining options, which is why this line of research gets attention — and also why the evidence needs to be unusually solid before anyone relies on it.
Takeaway for the community
Hyperbaric oxygen therapy for PTSD:
- showed a threshold pattern in this one dataset
- the cut-off that separated the two groups was 35% symptom reduction
- changes in intrusive and avoidance symptoms correlated most strongly with overall outcome
- those above the cut-off continued improving over the following three months
- was a post-hoc analysis of 56 patients and needs replication before it means anything clinically
HBOT Radar continues to track the latest science on trauma, neuroplasticity and biologically driven mental health treatments.
Study link: https://pubmed.ncbi.nlm.nih.gov/40847457/
Educational disclaimer
This content summarizes findings from published medical research for educational purposes only.
The hyperbaric chambers sold on this website are non-medical wellness devices and are not intended to diagnose, treat, cure, or prevent any disease.
The studies discussed here were conducted in clinical medical settings using medical-grade interventions. The inclusion of research summaries does not imply that similar outcomes can be achieved using non-medical wellness devices.
