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Research on Light Therapy and Depression

Depression is a mental health condition that affects the mental, physical and emotional health of an estimated 280 million people worldwide (Institute for Health Metrics and Evaluation, 2021). Photobiomodulation (PBM) shows promising results in helping symptoms of this condition.

Depression is a mental health condition that affects the mental, physical and emotional health of an estimated 280 million people worldwide (Institute for Health Metrics and Evaluation, 2021). Photobiomodulation (PBM) shows promising results in helping symptoms of this condition.

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Signs and Symptoms of Depression

While depression may look different for everyone, some common symptoms include (Mayo Clinic, 2022):

  • Persistent feelings of sadness, emptiness, or hopelessness
  • Frequent irritability, anger, or frustration, even over minor issues
  • Loss of enjoyment or interest in activities once found pleasurable, including hobbies, sports, or sex
  • Disturbed sleep patterns, such as insomnia or excessive sleeping
  • Fatigue and low energy, making everyday tasks feel exhausting
  • Heightened anxiety, restlessness, or a sense of agitation
  • Noticeably slowed thinking, speech, or physical movements
  • Overwhelming feelings of guilt or worthlessness, often with self-blame or dwelling on past failures
  • Difficulty with focus, memory, decision-making, or clear thinking
  • Recurring thoughts of death, suicidal ideation, or attempts at suicide

Biomarkers of Depression

  • Glowing neural cells connected by illuminated pathways, with blue and golden light against a soft background

    Neuroanatomical Differences

    People with depression are seen to have changes in cerebral blood flow and/or metabolism in the frontal-temporal cortex and caudate nucleus that lead to symptoms such as dysphoria, anhedonia, negative affect and helplessness (Cummings, 1993).

  • Neuron with glowing center and branching dendrites, connected to a cluster of mitochondria illustrated in blue

    Imbalance of Neurotransmitters

    Neuroimaging shows people with depression have reductions in gamma-aminobutyric acid (GABA) concentrations in the prefrontal and occipital cortex. Additionally, people with depression have decreased serotonin levels and dysfunctional serotonin receptors (Hasler, 2010).

  • Abstract flowing wave pattern with orange and blue curved lines on light background

    Genetic Predispositions

    Various twin and family studies have linked major depressive disorder to specific genes, including Val66Met, which controls brain derived neurotrophic factors (Lohoff, 2011).

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What Causes Symptoms of Depression?

Oftentimes there is not one cause of depression but can be the result of many sources. Some common causes of depression include (National Health Services, 2023):

  • Stressful events - Many people need time to process major life challenges, such as the loss of a loved one or the end of a relationship. The risk of depression can increase if you withdraw from family and friends and try to cope alone.
  • Personality - Certain personality traits, like low self-esteem or being highly self-critical, may make you more prone to depression. These tendencies can stem from genetics, early life experiences, or a mix of both.
  • Hormonal changes - hormonal changes, whether due to pregnancy, menstruation or menopause, can trigger the onset of depression.
  • Family history - Having a parent, sibling, or other close relative with depression raises the likelihood of developing it yourself. Severe depression, in particular, may be partly genetic, though life events also play a major role. A family history of depression does not guarantee you will experience it.
  • Other health conditions - pre-existing health conditions can contribute to depression, such as cancer, heart disease, or any conditions that cause long term pain.

Scientific Insights - PBMโ€™s Applications for Depression

  • PBM Combined with CBT Shows Improvements in Depression Scores

    One 2025 study tested whether adding transcranial infrared laser stimulation (TILS) could enhance internet-based cognitive behavioral therapy (iCBT) for major depressive disorder (Barrett, Beevers & Gonzalez-Lima). By week 12, the sham group showed a 43% reduction in depression scores, while the TILS group achieved a 56% reduction, reflecting about 30% greater improvement. The findings suggest that TILS can significantly boost the effectiveness of iCBT without adverse effects.

    See the study

  • PBM Alleviates Anxiety and Depression in Mice

    One study by Eshaghi et al. (2019) found that transcranial photobiomodulation (tPBM) with near-infrared light alleviated anxiety- and depression-like behaviors in mice subjected to chronic restraint stress, while also lowering elevated cortisol levels. Treatment increased serotonin and decreased nitric oxide concentrations in the prefrontal cortex and hippocampus, suggesting a neurochemical mechanism for its effects. Importantly, the antidepressant and anxiolytic benefits were dose-dependent. These findings support tPBM as a promising non-invasive intervention for mood regulation.

    See the study

  • Single Session PBM Reduces Depression and Anxiety Symptoms

    A pilot trial by Schiffer et al. (2009) found a single session of near-infrared photobiomodulation to the forehead significantly reduced symptoms of depression and anxiety in 10 patients, with 6 of 10 reaching remission on the Hamilton Depression Rating Scale and 7 of 10 on the Hamilton Anxiety Rating Scale at two weeks post-treatment. Immediate mood improvement, measured by the Positive and Negative Affect Scale occurred preferentially when the NIR was applied to the hemisphere with a more positive emotional valence.

    See the study

FAQs

What results can be expected and when?

Types of results and their timelines vary depending on the individuals. However, a combination of research and anecdotal evidence from providers suggests some expected results to be the following: improved language capabilities, improvements in emotional regulation, decreased repetitive behaviours, and improved social skills/engagement. While some clients may see results very quickly, others may take a few months.

What is mitochondrial dysfunction?

Mitochondrial dysfunction is a term that encapsulates dysfunction in various operations of the mitochondria. With mitochondria being the main energy producers of the cell, dysfunction can lead to reduced ATP (energy) production, increased oxidative stress, and difficulty maintaining healthy cell function. When mitochondria canโ€™t keep up with the bodyโ€™s energy demands or fail to remove damaged components, it can affect brain function, muscle strength, immune response, and overall vitality. Mitochondrial dysfunction is linked to many conditions, including fatigue, neurodegeneration, and metabolic disorders (Zong et al., 2024).

How many PBM sessions will I need?

Benefits can often be noticed within a few sessions, especially related to sleep and mental clarity. For cognitive improvements, consistent use over several weeks or months is typically recommended. As AD is often referred to as a neurodegenerative disease with genetic components, incorporating light therapy as a regular lifestyle habit can support overall brain health and give your brain the best chance to stay at its most performing level over time.

Is PBM safe?

Yes. PBM is FDA-cleared for various applications and has a strong safety profile. Itโ€™s non-invasive, painless, and has no known serious side effects when used as directed.

Learn More About PBM & Brain Health

References

Anxiety and Depression Association of America. (2021, April 27). Co-occurring disorders: Anxiety and related conditions. Retrieved September 2, 2025, from https://adaa.org/understanding-anxiety/co-occurring-disorders

leveland Clinic. (2024, July 3). Anxiety disorders: Causes, symptoms, treatment & types. Retrieved [your retrieval date], from Cleveland Clinic Health Library website: https://my.clevelandclinic.org/health/diseases/9536-anxiety-disorders#symptoms-and-causes

Eshaghi, E., Sadigh-Eteghad, S., Mohaddes, G., & Rasta, S. H. (2019). Transcranial photobiomodulation prevents anxiety and depression via changing serotonin and nitric oxide levels in brain of depression model mice: A study of three different doses of 810 nm laser. Lasers in Surgery and Medicine, 51(7), 634โ€“642. https://doi.org/10.1002/lsm.23082

Etkin, A., & Wager, T. D. (2007). Functional neuroimaging of anxiety: A meta-analysis of emotional processing in PTSD, social anxiety disorder, and specific phobia. American Journal of Psychiatry, 164(10), 1476โ€“1488. Helali, H., Samani, N., Tabeie, F., Eiliaei, S., & Kheradmand, A. (2025). The effectiveness of transcranial photobiomodulation therapy (tPBM) on reducing anxiety, depression, and opioid craving in patients undergoing methadone maintenance treatment: A double-blind, randomized, controlled trial. BMC Psychiatry, 25(1), Article 94. https://doi.org/10.1186/s12888-025-06555-3

Kerppers, F. K., Gonรงalves Dos Santos, K. M. M., Ribeiro Cordeiro, M. E., da Silva Pereira, M. C., Barbosa, D., Pezzini, A. A., Cunha, L. F., Fonseca, M., Bragnholo, K., Inoue Salgado, A. S., & Kerppers, I. I. (2020, March 7). Study of transcranial photobiomodulation at 945-nm wavelength: Anxiety and depression. Lasers in Medical Science, 35(9), 1945โ€“1954. https://doi.org/10.1007/s10103-020-02983-7

Martin, E. I., Ressler, K. J., Binder, E., & Nemeroff, C. B. (2009). The neurobiology of anxiety disorders: Brain imaging, genetics, and psychoneuroendocrinology. Psychiatric Clinics of North America, 32(3), 549โ€“575. https://doi.org/10.1016/j.psc.2009.05.004

Persaud, N. S., & Cates, H. M. (2023). The epigenetics of anxiety pathophysiology: A DNA methylation and histone modification focused review. eNeuro, 10(4), ENEURO.0109-21.2021. https://doi.org/10.1523/ENEURO.0109-21.2021

Zhao, A.-R. (2023). Stress can affect mitochondrial energy metabolism and AMPK/SIRT1 signaling pathway in rats. Brain Research Bulletin, 194, 110770. https://doi.org/10.1016/j.brainresbull.2023.110770

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