The light that can bring back your spark — where does the science stand today?
As the autumn–winter days grow shorter, many people feel as if their “battery” is slowly draining. Early darkness, persistent overcast skies, and a lack of natural light can combine into a low mood that goes beyond ordinary winter blues. Seasonal affective disorder (SAD) is a mood disorder specifically linked to light deprivation, and it can cause fatigue, sleep problems, increased appetite, low mood, and social withdrawal.
Classic light therapy (10,000-lux white light), psychotherapy, and—in some cases—medication can work well for many people, but not for everyone. That’s why there’s growing interest in complementary approaches that may support mood naturally during the darker months.
One such option is the use of red and near-infrared light. While large, well-controlled clinical trials have not yet definitively confirmed its effect specifically for seasonal depression, several small studies and plausible biological mechanisms suggest it’s a promising direction.
What is seasonal affective disorder (SAD)?
SAD (Seasonal Affective Disorder) is a mood disorder that most commonly begins in autumn, peaks in winter, and eases in spring. Its key trigger is a steep drop in natural daylight.
Light deprivation can:
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disrupt circadian rhythm
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interfere with melatonin production (sleep)
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lower serotonin levels (mood)
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affect signaling between nerve cells
The most common SAD symptoms include:
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persistent low mood and loss of motivation
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unusual fatigue and low energy
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sleeping too much or too little
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carb cravings and weight gain
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withdrawing socially
In other words, this “bad mood” has a biological basis.
How can red light help?
Red (630–670 nm) and near-infrared light (810–850 nm) can penetrate deeper through the skin and influence cellular-level processes that matter for mood, energy, and recovery.
Based on the current state of research, red and near-infrared light may support winter well-being in the following ways:
1. Supporting cellular energy production
Red and NIR light can stimulate mitochondria—the “power plants” of our cells.
As a result:
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ATP production (energy) may increase
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nerve cell function may improve
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oxidative stress may decrease
All of these are relevant to the biological drivers behind low mood and fatigue.
2. Fine-tuning mood-related hormones
Small studies suggest that red light may:
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increase serotonin levels
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stabilize melatonin production
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reduce cortisol levels (the stress hormone)
This isn’t an instant “mood-boosting light” effect—rather, a gentle, gradual rebalancing of physiology.
3. Sleep quality and easier mornings
Some studies suggest red light may:
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improve total sleep time
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reduce morning grogginess
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support stabilization of circadian rhythm
Sleep disruption is a major part of SAD, so these indirect effects may matter, too.
4. Nervous system recovery
Research on transcranial photobiomodulation (tPBM)—typically using a dedicated helmet—suggests that:
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attention and concentration may improve
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some depressive symptoms may decrease
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with no reported side effects
These are mostly small, early-phase studies, but the findings align with the proposed biological mechanisms.
What does the science say today? Promising—but not yet definitive
Here’s a fair summary of the current evidence:
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In depression more broadly, photobiomodulation has shown symptom improvements in multiple studies.
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For SAD specifically, there are still very few large, randomized studies designed directly for seasonal depression.
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Given the biology and smaller experiments, it’s logical to hypothesize that red light could help ease winter mood issues.
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But the evidence isn’t final yet—more research is needed.
The good news: across published studies so far, red light therapy has generally appeared safe and well-tolerated.
Which red light device might be suitable for winter low mood?
Based on research and practical experience, it’s worth paying attention to:
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Wavelength: 630–670 nm (red) and/or 810–850 nm (NIR)
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Irradiance: strong enough output to stimulate the upper body
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Safety certifications: CE, RoHS
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Session length: 10–20 minutes
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Distance: roughly 20–30 cm
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Timing: ideally in the morning or late morning so it doesn’t shift your sleep rhythm—or use a device setting designed specifically to support falling asleep.
Panels can be especially useful, as they cover a larger area and can stimulate deeper tissues.
Summary: A promising, natural tool for the winter months
Red and near-infrared light may:
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support cellular energy production
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contribute to hormonal and nervous-system balance
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improve sleep quality
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increase perceived energy levels
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be used safely at home
While definitive evidence for SAD is still pending, early studies and the biological rationale suggest that red light may have real potential to ease winter low mood—especially for those looking for natural, at-home options.
References:
1. Photobiomodulation and depression / mood
Ji, Z. et al. (2024).
Photobiomodulation improves depression symptoms: a systematic review and meta-analysis of randomized controlled trials.
https://pubmed.ncbi.nlm.nih.gov/37651208/
Cassano, P. et al. (2018).
Shining Light on Major Depressive Disorder: Transcranial Photobiomodulation—A Novel Treatment for Depression.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6007582/
2. Red light, sleep, and circadian rhythm
Pan, Y. et al. (2023).
Effects of red light on sleep and mood in healthy subjects.
https://www.frontiersin.org/articles/10.3389/fpsyt.2023.1200350/full
Giménez, M. et al. (2023).
Effects of Near-Infrared Light on Well-Being and Health in Human Subjects with Mild Sleep-Related Complaints.
https://research.rug.nl/en/publications/effects-of-near-infrared-light-on-well-being-and-health-in-human-
Jung, J. et al. (2024).
Photobiomodulation and Its Therapeutic Potential in Sleep.
https://sleepmedres.org/journal/view.php?doi=10.17241/smr.2024.02593
3. Light deprivation, mood, and SAD (general light research)
Lam, R. et al. (2018).
Light therapy for seasonal affective disorder: a review of the evidence.
https://pubmed.ncbi.nlm.nih.gov/29319254/
Reeves, G. et al. (2012).
Improvement in Depression Scores After 1 Hour of Light Therapy Treatment in Patients With Seasonal Affective Disorder.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5336550/
Wan, S. et al. (2025).
Effectiveness of visible light for seasonal affective disorder.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12237333/
4. Mechanistic (mitochondria, hormones, immune system)
Hamblin, M. R. (2016).
Mechanisms and applications of the anti-inflammatory effects of photobiomodulation.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5523874/
Barrett, D. & Gonzalez-Lima, F. (2013).
Transcranial Infrared Laser Stimulation Produces Beneficial Cognitive and Emotional Effects.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3759274/
