A Sham-Controlled Trial of HBOT for Veterans With Combat-Related PTSD
A randomized, sham-controlled trial in male veterans reports reductions in PTSD and depression scores after HBOT. How the sham design works, and where the limits lie.
- A randomised, sham-controlled trial in the Journal of Clinical Psychiatry tested HBOT in male veterans with combat-associated PTSD at Israel's Shamir Medical Center.
- Both arms did 60 daily 90-minute sessions; the active group breathed 100 percent oxygen at 2 ATA while the sham group breathed ordinary air at a token 1.02 ATA.
- The trial reported significant reductions in PTSD severity on the CAPS-5, alongside reductions in depression measured with the BDI-II and DASS-21.
The trial
The Journal of Clinical Psychiatry published a randomised, sham-controlled clinical trial of hyperbaric oxygen therapy for veterans with combat-associated PTSD. The study was run at the Sagol Center for Hyperbaric Medicine and Research at Shamir Medical Center in Israel, with recruitment reported between February 2020 and July 2023.
Participants were male veterans, aged roughly 25 to 60, who met criteria for combat-associated PTSD with a Clinician-Administered PTSD Scale for DSM-5 (CAPS-5) score above 20. That entry threshold matters: it means the cohort started with clinically meaningful symptom levels rather than mild or borderline cases. Combat-associated PTSD is often long-standing and can respond only partly to standard psychotherapy and medication, which is part of why alternative approaches are studied at all.
How a sham-controlled HBOT trial is built
Blinding hyperbaric oxygen is difficult, because patients can often sense that they are being pressurised. To address this, both arms entered a chamber for 60 daily sessions of 90 minutes. The active arm breathed 100 percent oxygen at 2 atmospheres absolute (ATA); the sham arm breathed 21 percent oxygen - ordinary air - at 1.02 ATA, a token pressurisation, with 5-minute air breaks. The aim is that participants experience a comparable ritual while only one group receives a meaningful oxygen dose.
This design is the study's main strength. A sham comparator helps separate the physiological effect of oxygen from the powerful expectation effects that accompany an intensive, high-touch treatment. No sham is perfect, but a low-pressure air exposure is a serious attempt to keep both participants and assessors genuinely blinded.
What the authors reported
The trial reported significant reductions in PTSD symptom severity on the CAPS-5, alongside reductions in depression symptoms measured with the Beck Depression Inventory (BDI-II) and the DASS-21. In other words, the signal was not limited to core PTSD symptoms but extended to mood measures collected at the same time.
The results should be read within the trial's boundaries. The cohort was male veterans with combat-associated PTSD, so the findings do not automatically transfer to women, to civilians, or to PTSD arising from other causes. A single trial, however carefully controlled, is a contribution to the evidence base rather than the last word. It also does not, on its own, establish how long any improvement lasts, since durability depends on follow-up beyond the treatment window.
Reading this in context
Independent replication by other groups, in other populations, is what turns a promising controlled trial into a reliable finding. HBOT for PTSD sits in an active but still-developing research area, and results have been mixed across studies with different designs and populations. The pressures used here - 2 ATA in a sealed chamber - are a clinical-grade exposure, not something reproduced by low-pressure consumer equipment; our overview of low-pressure devices at soft-sided chambers explains why that distinction matters when reading trial protocols.
Trauma-related conditions require individualised, professional care. If HBOT is of interest as part of that care, the appropriate next step is a conversation with a physician or mental-health clinician rather than self-directed treatment.
Frequently asked questions
+How does a sham-controlled HBOT trial keep patients blinded?
Blinding is hard because patients can often sense pressurisation. In this trial both groups entered a chamber for 60 daily 90-minute sessions, but only the active arm breathed 100 percent oxygen at 2 ATA; the sham arm breathed ordinary air at a token 1.02 ATA. The aim is that everyone experiences a comparable ritual while only one group receives a meaningful oxygen dose - no sham is perfect, but this is a serious attempt at genuine blinding.
+Do these PTSD results apply to everyone?
No. The cohort was male veterans with combat-associated PTSD (CAPS-5 above 20), so the findings do not automatically transfer to women, civilians, or PTSD from other causes. A single controlled trial is a contribution to the evidence rather than the last word, and it does not by itself establish how long any improvement lasts. Trauma-related conditions call for individualised care, best explored with a physician or mental-health clinician.
+What did the trial find beyond PTSD symptoms?
Alongside significant reductions in PTSD severity on the CAPS-5, the trial reported reductions in depression symptoms measured with the Beck Depression Inventory (BDI-II) and the DASS-21. In other words, the signal extended to mood measures collected at the same time, not just core PTSD symptoms. The study does not, on its own, show how durable these changes are, since that depends on follow-up beyond the treatment window.