If you’ve searched for light therapy and long COVID, you’ve probably seen a headline about a new trial showing cognitive gains. There is a real trial behind those headlines. It’s worth reading properly, because what it found is more interesting — and more useful to you — than the headline version.
The study
Lim and colleagues published a randomized, double-blind, sham-controlled pilot trial in eClinicalMedicine in 2026. Forty-three people with post-COVID cognitive dysfunction were randomly assigned to either an active device or an identical-looking sham, and neither participants nor assessors knew which was which. The device delivered 810 nm near-infrared light through intranasal and transcranial LEDs, 20 minutes a day, six days a week, for eight weeks.
That design is the right design. Sham-controlled and double-blind is what separates a real signal from expectation, practice effects and natural recovery — all of which are substantial in cognitive testing and in long COVID.
What it found
The primary endpoint was not met. The composite cognitive score difference between active and sham at Day 56 was 0.043, with a 95% confidence interval of −0.007 to 0.092, and a p-value of 0.088. By the standard the researchers set before they started, the trial did not demonstrate a benefit.
Three further findings deserve to be reported alongside that:
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Participants under 45 did show a statistically significant improvement (p=0.028). But this is a subgroup of a trial that missed its primary endpoint, with 43 people in total. Subgroup findings in that situation generate hypotheses. They don’t establish effects.
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One attention task (Feature Match) improved significantly at two timepoints.
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The Fatigue Assessment Scale favored the sham group (p=0.038).
That last one matters most, and it’s the one you won’t see in the marketing. Fatigue is the defining symptom of long COVID for most people who have it. The only rigorous fatigue measurement in the only randomized trial of this therapy pointed the other way.
What the trial does not tell you
The device used was intranasal and transcranial — light delivered non-invasively to the head. It was not intravenous laser, and it was not whole-body.
This distinction gets erased constantly in clinic marketing, and it shouldn’t be. Different delivery routes mean different wavelengths, different doses reaching different tissues, and different risk profiles. A trial of an intranasal LED device is not evidence about an intravenous procedure. If a clinic cites this trial to sell you intravenous laser, that tells you something about the clinic.
For intravenous laser specifically in long COVID, the published human evidence is one open-label study of six patients with no control group (Chang et al., QJM, 2025).
Why we’re telling you this
We offer photodynamic and laser therapy at Venturis, and we’re running a case study series in post-COVID presentations. We’re doing that precisely because the evidence is as thin as this article describes.
If someone tells you this therapy is proven for long COVID, they either haven’t read the trial or are hoping you won’t. The honest position is that it’s an open question worth investigating carefully, in people who understand that’s what they’re signing up for.
References
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Lim L, Hosseinkhah N, Van Buskirk M, et al. Photobiomodulation for cognitive dysfunction (brain fog) in post-COVID-19 condition: a randomized double-blind sham-controlled pilot trial. eClinicalMedicine. 2026;92:103730. doi:10.1016/j.eclinm.2025.103730
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Chang CC, Li YH, Chang ST, Chen HH. Impact of intravenous laser irradiation of blood on cognitive function and molecular pathways in long COVID patients: a pilot study. QJM. 2025;118(7):481–488. doi:10.1093/qjmed/hcaf050. PMID: 39960888
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Bowen R, Arany PR. Use of either transcranial or whole-body photobiomodulation treatments improves COVID-19 brain fog. J Biophotonics. 2023;16(8):e202200391. doi:10.1002/jbio.202200391. PMID: 37018063
Reviewed by Dr. Alvin Philipose, B.S., B.S., DC, ICCP, Venturis Clinic, Oklahoma City, Oklahoma. Last reviewed: August 2026.
Important information: Photobiomodulation, photodynamic therapy and intravenous laser therapy are investigational for post-COVID conditions and are not approved by the U.S. Food and Drug Administration for the treatment, cure, mitigation or prevention of any disease. Nothing in this article is a claim of efficacy, and no outcome is promised or implied. Individual results vary. This article is educational and does not constitute medical advice, diagnosis or treatment.