This article is part of the HBOT Radar series, where we summarize the latest published hyperbaric oxygen therapy research.
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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.
📌 After a Stroke, Depression Hits Hard. This Sham-Controlled Trial Tested Whether Oxygen Could Help
🔍 What this study explored
Here's a statistic that doesn't get enough attention: somewhere between 29% and 52% of stroke survivors develop depression afterward. Not just feeling low — clinical, measurable depression that impairs recovery, damages quality of life, and increases the risk of dying by a staggering 35-fold compared to non-depressed stroke survivors.
Post-stroke depression (PSD) isn't just "being sad about having a stroke." It has a biological basis. When a stroke damages brain tissue, it disrupts the signaling of critical neurotrophic factors — brain chemicals like BDNF (brain-derived neurotrophic factor) and β-NGF (beta-nerve growth factor) that are essential for keeping neurons alive, maintaining connections between brain cells, and regulating mood. When these chemical messengers drop, the neural circuitry that supports emotional wellbeing starts to malfunction.
Current treatments — mainly antidepressant medications — help some patients, but response rates are inconsistent, and many stroke survivors are already on multiple medications with complex interactions. There's a real clinical need for alternatives.
This is where a Chinese research team asked a bold question: if HBOT can boost neurotrophic factor levels in the brain, could it directly address the biological roots of post-stroke depression? And — crucially — they designed a proper randomized, double-blind, sham-controlled trial to test it. The researchers themselves note that this is the first RCT of its kind: the first to combine rigorous sham control with simultaneous measurement of both depression symptoms and the underlying neurotrophic mechanisms.
🌬️ HBOT protocol used in this study
The study design was rigorous — and the sham protocol deserves special attention, because this is where many HBOT trials stumble.
- HBOT group (n=29): 100% oxygen via mask at 2.0 ATA for 90 minutes, with 5-minute air breaks every 20 minutes. 20 sessions total, five days per week over four weeks. Conducted in a multi-place hyperbaric chamber.
- Sham group (n=32): 21% oxygen (normal room air) at 1.03 ATA for 90 minutes. To make the blinding believable, the chamber pressure was briefly raised to 1.2 ATA during the first five minutes — just enough for participants to feel the ear-clearing sensation — then gradually reduced to 1.03 ATA over the next five minutes.
Why this sham design matters: A common criticism in HBOT research (notably raised by Dr. Paul Harch and others) is that many trials use 1.3 ATA with 100% oxygen as their "sham" — which isn't truly inert, because it's actually a low-dose HBOT treatment. This study avoided that trap. The sham group breathed normal air at essentially sea-level pressure. The brief 1.2 ATA bump was purely for blinding purposes and lasted only five minutes — not long enough to deliver any therapeutic oxygen dose. This is about as close to a true placebo as you can get in HBOT research.
Did the blinding work? Yes. When asked to guess their group, participants were at coin-flip accuracy: 51.7% correct in the HBOT group, 53.1% in the sham group. They genuinely couldn't tell.
- Duration: 4 weeks (20 sessions)
- Assessments: Baseline, week 2, and week 4
- Outcome measures: Hamilton Depression Rating Scale (HAMD-17), serum BDNF and β-NGF levels, NIHSS (neurological deficit score), and Modified Barthel Index (functional independence)
- Analysis: Modified intention-to-treat, with multiple imputation for the small amount of missing data (7.6%)
66 patients were initially randomized; 61 completed the trial (5 withdrew — 4 from the HBOT group, 1 from sham).
Important: This study used clinical-grade HBOT at 2.0 ATA with 100% medical oxygen in a hospital setting. These conditions are not comparable to consumer or wellness-grade chambers.
📊 Key findings
Depression scores dropped — and the difference was real
This is the headline: depression scores on the HAMD-17 scale decreased significantly more in the HBOT group compared to the sham group. The difference was already detectable at week 2 (p = 0.017) and became even stronger by week 4 (p < 0.001).
That's not a trend. That's not "approaching significance." That's a statistically robust finding from a properly blinded trial where even the patients couldn't tell whether they were getting real treatment.
The biological mechanism showed up in the blood
Here's what elevates this study above a simple "did patients feel better" finding: the researchers measured the neurotrophic factors that theory predicts should change if HBOT is actually affecting the brain's repair machinery.
Serum BDNF levels were significantly higher in the HBOT group compared to sham (p < 0.01), with a large effect size (Cliff's d = 0.54). The between-group difference in adjusted BDNF was 966 pg/mL.
β-NGF levels were also significantly elevated in the HBOT group (p < 0.01), with a medium effect size.
These aren't just incidental lab findings. They directly connect to the mechanism.
The smoking gun: depression improvement correlated with neurotrophic factor increases
This is the most scientifically compelling part. The reduction in depression scores wasn't just happening alongside the neurotrophic factor increases — they were mathematically correlated:
- BDNF increase correlated with HAMD reduction: r = 0.66 (p < 0.05) — a strong correlation
- β-NGF increase correlated with HAMD reduction: r = 0.47 (p = 0.01) — a moderate correlation
In other words: the patients whose neurotrophic factors increased the most were the same patients whose depression improved the most. That's exactly what you'd predict if HBOT is working through neurotrophic mechanisms rather than just a placebo effect.
The effect held across subgroups
Exploratory analyses showed that the HBOT benefit was consistent regardless of stroke type (ischemic vs hemorrhagic) and age group (above or below 65). No significant interactions were found, suggesting the effect isn't limited to a specific subset of patients.
No adverse events
No significant adverse reactions were reported in either group during the 4-week treatment period.
🧠 Why this study matters
Let's put this in context. A 2020 meta-analysis of 27 RCTs involving 2,250 patients had already found that HBOT was associated with higher response rates (69.4% vs 51.2%), reduced depression severity, and fewer adverse events compared to controls in PSD. But most of those trials had methodological weaknesses — poor sham controls, lack of blinding, no investigation of biological mechanisms.
This new trial addresses those gaps directly. It's double-blind. The sham was effective (participants genuinely couldn't tell which group they were in). And it measures the biological pathway, not just the clinical outcome.
That said — the honest caveats:
- 61 patients is still relatively small. The researchers themselves call this a "preliminary trial" and explicitly state that larger trials with extended follow-up are needed.
- 4 weeks is short. Depression is a chronic condition. We don't know if the benefits persist after treatment stops, or how long they last.
- Single center. All patients came from hospitals in Ningbo, China. Replication in other populations and settings would strengthen the findings considerably.
- The specific HBOT protocol details (exact ATA pressure) aren't fully available from the abstract and search results — future readers should consult the full publication for protocol specifics.
- Correlation isn't causation. The correlation between BDNF/β-NGF increases and depression improvement is highly suggestive of a causal mechanism, but it doesn't definitively prove one. Other unmeasured factors could play a role.
Despite these caveats, this is one of the strongest pieces of evidence to date connecting HBOT to a specific neurobiological mechanism in a psychiatric condition. For a field that has long been criticised for lacking rigorous trial design, this study raises the bar considerably.
📌 Takeaway for the community
- In the first double-blind, sham-controlled RCT of its kind, 4 weeks of HBOT was associated with significantly greater reduction in post-stroke depression symptoms compared to sham treatment — detectable by week 2 and robust by week 4
- Serum levels of two key brain-repair chemicals (BDNF and β-NGF) were significantly elevated in the HBOT group, and their increases correlated with the degree of depression improvement
- The sham blinding worked — participants couldn't tell whether they were receiving real or sham HBOT, strengthening confidence that the results aren't driven by placebo effects
- With 61 patients, a single center, and only 4 weeks of follow-up, larger and longer trials are needed to confirm the findings and establish long-term benefit
- This study used clinical-grade HBOT in a hospital setting — not comparable to consumer wellness chambers
Tang M, Gong S, He J, Wu X, Shi M, Yang M, Shi L, Huang L, Li L, Zhou D, Zhao Y. Hyperbaric Oxygen Therapy Upregulates Neurotrophic Factors to Ameliorate Post-Stroke Depression: A Randomized Sham-Controlled Trial. Neuropsychiatr Dis Treat. 2026;22:573494. doi: 10.2147/NDT.S573494.
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.
