Mental Health
Red light therapy and depression: what the evidence shows
A 2024 meta-analysis of 11 randomised controlled trials found red light therapy reduces depression symptoms with a moderate effect size. Here is what the research shows - and where it stops.
Depression, mitochondria, and light
If you are reading this, there is a reasonable chance you or someone close to you has been through the loop: trying one antidepressant, then another, adjusting doses, dealing with side effects, wondering if there is something else worth trying. That is not a niche experience. Roughly one in three people with major depressive disorder do not respond adequately to first-line antidepressants - and that gap has driven serious research into non-pharmacological approaches. Photobiomodulation is one of them.
The biological connection between light and mood is not new. What is new is the mechanistic understanding. Research published since 2020 has established that depression is associated with mitochondrial dysfunction, neuroinflammation, and impaired neuroplasticity - three processes that red and near-infrared light directly influences at the cellular level.
The primary target is cytochrome c oxidase - an enzyme inside your cells' mitochondria (the parts that generate energy) that absorbs red and near-infrared light and responds by producing more ATP, the fuel cells run on. In brain tissue, that means neurons have more energy to work with, oxidative stress (a form of cellular wear) reduces, and the inflammatory processes now understood to be central to depression get dialled down.
What the clinical evidence shows
The most comprehensive evaluation to date came from a 2024 systematic review and meta-analysis published in Frontiers in Psychiatry (Ji et al.). Searching ten databases and screening 3,265 studies, the authors identified 11 randomised controlled trials with a total of 407 participants. The pooled result: photobiomodulation produced a statistically reliable reduction in depression symptoms, with a standardised mean difference of -0.55 and a 95% confidence interval of -0.75 to -0.35. In clinical terms, that is a moderate effect size - comparable to the effect of antidepressant medication in some meta-analyses.
The ELATED trial series from Massachusetts General Hospital and Harvard Medical School represents the most rigorous individual trial evidence. ELATED-2 (2018) demonstrated reductions in Hamilton Depression Rating Scale scores using 823nm near-infrared light applied transcranially. ELATED-3 tested whether very low irradiance would still produce antidepressant effects - and found it did not, establishing that dose matters: below a certain threshold of light energy delivered, the brain does not respond. That finding is actually informative - it confirms the effect is real and dose-dependent, not just a placebo response.
A 2025 review in Theranostics (Wang et al., Augusta University and LSU Health Sciences) catalogued the neurobiological evidence across publications from 2014 to 2024. The picture that emerges: photobiomodulation can improve blood flow to the brain, reduce neuroinflammation (chronic low-level brain inflammation that impairs mood and cognition), slow the death of brain cells, encourage the growth of new ones, and increase neurotrophins - proteins the brain uses to maintain and repair neural connections. These are not peripheral effects - they sit at the core of what depression does to the brain and what recovery requires.
Transcranial vs systemic application - and why it matters for panel users
Most of the clinical trial evidence involves transcranial photobiomodulation - light applied directly to the scalp, targeting the prefrontal cortex (the front part of the brain responsible for mood regulation, decision-making, and emotional processing). This is the most studied delivery route, and the one used in the ELATED trials. Near-infrared at 810-850nm penetrates skull tissue, reaching the cortex with sufficient energy to produce measurable effects on brain activity.
However, the Theranostics 2025 review and supporting research make clear that applying light directly to the head is unlikely to be the only pathway. The authors describe an indirect effect - where light delivered to skin and tissue elsewhere in the body triggers systemic changes that subsequently influence brain function. The proposed mechanisms include calming the autonomic nervous system (the system that governs your stress response), supporting serotonin production from peripheral tissues, and reducing the whole-body inflammation that feeds neuroinflammation in the brain.
This matters for anyone using a full-body panel rather than a dedicated head device. A 2024 research protocol examining systemic and abdominal photobiomodulation for major depressive disorder noted that exposure to peripheral tissues can positively influence neurotransmitter production - including serotonin - and that the gut-brain axis may be one of the routes through which remote application affects mood. The systemic anti-inflammatory effects documented across multiple areas of red light therapy research are also relevant here: chronic inflammation is now a recognised driver of depression, and reducing that inflammatory load systemically creates better conditions for mood regulation.
Honest limitation
The systemic pathway evidence is more preliminary than the transcranial evidence. The RCTs with the strongest depression outcomes used targeted near-infrared devices applied to the head, not full-body panels. The indirect mechanisms are biologically plausible and supported by preclinical and mechanistic data - but they have not yet been tested in the same controlled trial designs. Worth keeping that in mind.
The inflammation connection
One reason the photobiomodulation evidence for depression has strengthened is that the model of depression itself has shifted. The serotonin deficit hypothesis - the idea that depression is fundamentally a chemical imbalance corrected by SSRIs - has faced sustained scientific criticism over the past decade. The neuroinflammatory model has taken on more weight: elevated inflammatory markers including CRP, IL-6, and TNF-alpha (proteins the body releases when it is under chronic stress or fighting inflammation) are consistently found in depressed patients, and treatments that reduce that inflammation frequently improve mood as a secondary effect.
Red light therapy's anti-inflammatory effect is among its best-evidenced properties - covered in depth in the longevity blog - and it works by suppressing the molecular switches (including the NF-kB pathway) that trigger inflammatory signalling throughout the body. In the context of depression, reducing that systemic inflammation means less of it reaching the brain - and the brain, under less inflammatory load, functions better.
This also connects to sleep. Poor sleep is both a symptom and a driver of depression, and red light therapy's documented effects on sleep quality may contribute to mood improvements that are difficult to cleanly separate from a direct neurological effect. Better sleep reduces inflammatory markers, supports cortisol regulation, and helps restore the brain's capacity to adapt and recover - something depression steadily erodes. The pathways run together.
Where the evidence stands and what to expect
The honest summary: photobiomodulation has a more credible evidence base for depression than most people expect, and a less conclusive one than the most enthusiastic accounts suggest.
What the evidence supports: red and near-infrared light applied consistently - whether transcranially or systemically - can reduce depression symptom scores via measurable neurobiological mechanisms. The effect size from the best meta-analysis is moderate and statistically reliable. The therapy is well-tolerated with a low side-effect profile, which matters in a population where medication side effects are a frequent reason for treatment discontinuation.
What the evidence does not yet support: a direct comparison with standard pharmacological treatment. Larger, longer trials with standardised protocols are still needed. The optimal wavelength, irradiance, session duration, and delivery site for depression specifically have not been definitively established. The 2025 wearable tPBM RCT published in the Journal of Affective Disorders (Guu et al., 48 participants, 8 weeks) found hypnotic effects but not statistically reliable antidepressant effects with self-administered use - a reminder that delivery method and dose matter.
For people already using red light therapy for other reasons - skin, sleep, recovery, inflammation - noticing some improvement in mood is a reasonable secondary expectation. For people considering it primarily for depression, it is most accurately described as a low-risk, evidence-supported complement to other treatment, not a standalone solution. That framing respects both the evidence and the people in the middle of something genuinely difficult.
What does using it actually look like
Most of the clinical trials that found positive outcomes ran sessions of 10-20 minutes, applied daily or near-daily, over 4-8 weeks. That is the window where measurable changes in depression scores typically showed up - not after a few days, and not from sporadic use. Consistency matters more than session length in most of the protocols.
For full-body panel use, the most relevant targets are the upper body and head-adjacent areas where systemic circulation is richest. You do not need a dedicated head device to access the systemic and anti-inflammatory pathways described above - though if transcranial application is your primary goal, a targeted near-infrared device is the more direct route.
One practical note: several trials specifically found that sleep improvement appeared before mood improvement. If you are tracking effects, sleep quality is often the first signal that something is shifting - and given the relationship between sleep and depression, that is the right place to start paying attention.
What about anxiety
Most people searching this topic are not dealing with depression in isolation. Anxiety and depression overlap significantly - and the photobiomodulation research, while thinner on the anxiety side, points in the same direction.
A 2019 pilot study by Maiello et al. at Massachusetts General Hospital found that transcranial near-infrared light may be a promising approach for generalised anxiety disorder, with participants reporting reduced anxiety scores after treatment. The mechanistic case is plausible for the same reasons it is for depression: less brain inflammation, better cellular energy in the prefrontal cortex (the part of the brain that helps regulate fear and worry), and improved sleep all have downstream effects on how the brain handles anxiety.
The honest caveat: the anxiety evidence is earlier-stage than the depression evidence. The trials are smaller, fewer, and less standardised. It is worth being aware of rather than leaning on. But for someone dealing with both, the overlap in proposed mechanisms means a consistent red light practice is not doing two separate things - it is likely addressing some of the same underlying biology.
Sources
Clinical-grade red and near-infrared. Available now.
NovaThera panels cover the full red and near-infrared spectrum with published irradiance data. Consistent daily use is where the evidence is built.