Can Light Influence Mood?
Mood is often treated as something that happens entirely inside the brain. But our emotional health is connected to a much larger network of biological systems. Sleep, chronic pain, inflammation, physical health, stress, and cellular energy can all influence how we feel.
That makes a new study on photobiomodulation and depressive symptoms particularly interesting.
Researchers conducted a systematic review and meta-analysis of 18 photobiomodulation studies involving 918 participants. Overall, photobiomodulation was associated with a moderate, statistically significant reduction in depressive symptoms compared with control groups.¹
Most of the studies were randomized controlled trials. Participants included people diagnosed with major depressive disorder as well as people experiencing depressive symptoms alongside chronic pain, fibromyalgia, insomnia, post-concussion symptoms, and other conditions.
The Connection Between Cellular Energy and Mood
One possible explanation begins with the mitochondria. Mitochondria produce ATP, the energy our cells use to carry out their work. Researchers studying depression have identified associations with mitochondrial dysfunction, altered cerebral energy metabolism, oxidative stress, and inflammation.
Photobiomodulation influences many of these same biological systems.
Red and near-infrared light can affect mitochondrial activity and ATP production while also influencing oxidative stress, inflammatory signalling, and cerebral blood flow.¹
This does not mean low cellular energy is a single cause of depression. Mood is far more complex than that.
But it does help explain why researchers are interested in photobiomodulation as a possible complement to established approaches to mental-health care.
Mood May Be About More Than the Brain
One of the most interesting findings in the meta-analysis was that benefits were not limited to treatments directed at the head. Studies that applied photobiomodulation to areas of the body showed a larger pooled effect on depressive symptoms than studies using brain-targeted treatment. The authors propose that these approaches may influence mood through different routes.
Brain-targeted photobiomodulation may act more directly on cortical cells through mitochondrial activity, cerebral blood flow, and neuroplasticity.
Systemic photobiomodulation may instead influence broader processes such as inflammation, oxidative stress, mitochondrial function, and physical symptoms elsewhere in the body.
The two groups of studies differed substantially, so the finding should not be interpreted to mean that whole-body treatment has been proven superior. The larger idea is more interesting anyway: Mood may not be only a “brain problem.” The systems involved in energy, inflammation, pain, sleep, and physical health may all be part of the picture.
Does Treatment Duration Matter?
The researchers also looked at which treatment characteristics appeared to influence the results. Longer overall treatment duration was associated with larger reductions in depressive symptoms. By contrast, simply increasing treatment frequency or light intensity was not associated with greater benefits.¹
Photobiomodulation has what researchers call a biphasic dose response. In simple terms, more light is not necessarily better.
This reinforces why wavelength, dose, treatment location, duration, and the individual receiving treatment all matter.
How Strong Is the Evidence?
The overall result was statistically significant, and the authors found little evidence that publication bias was responsible for the effect. Even after adjusting for potentially missing studies, the effect remained statistically significant.
There are still important limitations.
The included studies used different wavelengths, doses, treatment sites, clinical populations, and protocols. Three of the 18 studies were not randomized, and individual studies were generally small.
Photobiomodulation is therefore not a replacement for psychotherapy, medication, or care from a qualified mental-health professional.
What this study does provide is a stronger signal that deserves continued research.
Across 18 studies, photobiomodulation was associated with reduced depressive symptoms. Just as interestingly, the research suggests that the relationship between light and mood may involve not only the brain, but the broader biological environment in which the brain operates.
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We’ll continue following this research as scientists learn more about photobiomodulation, cellular energy, inflammation, and mood.
If you’re curious about how photobiomodulation may complement your broader care plan, connect with the RegenClinic team. We’re always happy to answer your questions.
Call or text us at 250-208-4218
Email: hello@regenclinic.ca