Every mood swing, seizure, and intrusive memory shares a common electrical currency: a ratio between the brain’s gas pedal and its brakes.
Neuroscientists call it excitation-inhibition balance, and when it tips too far in either direction, the result can look like epilepsy, autism, depression, or post-traumatic stress. A review published in Neuroscience on September 11, 2026 makes the case that photobiomodulation, the clinical name for red and near-infrared light therapy, may be able to nudge that ratio back toward equilibrium.
What excitation-inhibition balance actually means
Every signal that moves through the brain is either excitatory or inhibitory. Glutamate is the primary excitatory neurotransmitter, pushing neurons to fire, while GABA is the primary inhibitory one, holding that firing in check.
Healthy cognition depends on these two systems staying in a tight, dynamic ratio. Tip it toward excess excitation and the brain becomes prone to seizures, anxiety, and sensory overload, while tipping toward excess inhibition can look like sedation, blunted mood, or cognitive slowing.
Researchers have linked disrupted excitation-inhibition balance to epilepsy, autism spectrum disorder, schizophrenia, major depression, and traumatic brain injury. The new Neuroscience review treats this ratio as a unifying mechanism that connects otherwise unrelated diagnoses, and asks whether a single intervention, light, could act on it directly.
How light reaches into brain chemistry
Photobiomodulation uses red and near-infrared wavelengths, typically in the 600 to 1100 nanometer range, delivered through the scalp or skull. The light does not heat tissue or damage cells the way ultraviolet radiation does.
Instead, it is absorbed by cytochrome c oxidase, an enzyme in the mitochondrial membrane that drives the final step of cellular energy production. Photobiomodulation researcher Michael Hamblin, formerly a principal investigator at Massachusetts General Hospital, has described this absorption as the trigger for a cascade: more ATP, a brief burst of reactive oxygen species, and activation of transcription factors that switch on genes tied to cell survival and antioxidant defense.
The Neuroscience authors extend that mitochondrial story into circuit-level territory. Their argument is that boosting mitochondrial efficiency in inhibitory interneurons, the GABA-releasing cells that keep excitatory signaling in check, could restore the energy supply those cells need to fire reliably and dampen runaway excitation elsewhere in the network.
Why inhibitory neurons may be the real target
Inhibitory interneurons are metabolically expensive to run. They fire at high, sustained rates to keep excitatory pyramidal neurons from spiraling into synchronized, seizure-like activity, and that constant firing burns through mitochondrial energy faster than most other cell types in the brain.
When mitochondrial function declines, whether from aging, injury, or chronic stress, inhibitory neurons are disproportionately affected. The review frames this as a plausible reason why so many neuropsychiatric conditions trace back to insufficient inhibition rather than excess excitation: the brakes wear out before the gas pedal does.
If photobiomodulation preferentially supports these energy-hungry inhibitory cells, restoring their firing capacity could recalibrate the excitation-inhibition ratio from the inhibitory side, rather than by simply suppressing excitatory signaling, which is how most anticonvulsant and anxiolytic drugs work.
Which disorders fit this framework
The excitation-inhibition hypothesis did not originate with photobiomodulation research. Neuroscientists John Rubenstein and Michael Merzenich proposed in 2003 that autism spectrum disorder could stem from a shifted cortical ratio favoring excitation, a model that has since shaped two decades of autism neuroscience.
In schizophrenia, postmortem studies led by psychiatrist David Lewis at the University of Pittsburgh have repeatedly found reduced GABA-synthesizing enzyme activity in the prefrontal cortex, consistent with an inhibitory deficit rather than an excitatory excess. Epilepsy offers the most direct evidence: certain forms, including Dravet syndrome, are caused by mutations in sodium channels expressed almost exclusively on inhibitory interneurons, which explains why the seizures are so severe and so difficult to treat with conventional anticonvulsants.
Post-traumatic stress disorder fits a related but distinct pattern, where an overactive amygdala goes underregulated by prefrontal inhibitory circuits that have lost some of their restraining capacity. The Neuroscience review situates photobiomodulation as a potential lever across all four conditions, not because it targets any single disease process, but because it targets the shared cellular bottleneck, mitochondrial energy in inhibitory neurons, that shows up in each one.
What the clinical evidence shows so far
The translational picture is earlier stage than the mechanism, but it is not empty. Psychiatrist Paolo Cassano, who has run transcranial photobiomodulation trials out of Massachusetts General Hospital and Harvard Medical School, has reported mood improvements in patients with major depressive disorder following repeated near-infrared sessions targeting the prefrontal cortex.
Speech-language researcher Margaret Naeser, at the VA Boston Healthcare System, has published case series suggesting transcranial light improves cognitive function in people with chronic traumatic brain injury, a population in which excitation-inhibition imbalance is well documented. Separately, Francisco Gonzalez-Lima at the University of Texas at Austin has shown that a single session of transcranial infrared light can improve sustained attention and working memory in healthy adults, hinting that the mechanism operates even without an existing disorder to correct.
None of these trials, and none of the animal work the Neuroscience review draws on, prove that photobiomodulation cures or treats any specific diagnosis. What they consistently show is a shift in measurable brain activity and self-reported symptoms that lines up with the excitation-inhibition framework the review proposes.
The gap between mechanism and medicine
A mechanistic review is not a green light for self-treatment. The Neuroscience authors are explicit that dosing parameters, wavelength, session duration, and how deep light actually penetrates the skull remain unresolved variables across the field.
Most published trials use clinical-grade transcranial devices under supervision, not the consumer red light panels marketed for skin and recovery. People curious about the category as a wellness tool, rather than a psychiatric intervention, are more likely to encounter it through panels reviewed for physical recovery, such as the Hooga Pro red light therapy panel or the Joovv Solo 3.0, which are built around skin and muscle tissue exposure rather than transcranial dosing.
The distance between a panel that reddens skin at the surface and a device calibrated to reach cortical interneurons is significant, and the review is careful not to conflate the two.
Where the research goes next
The Neuroscience authors call for standardized dosimetry, larger randomized trials across specific diagnoses, and imaging studies that can directly measure whether GABAergic tone actually shifts after treatment in humans, not just in rodent models. Until that data exists, the excitation-inhibition framework remains a compelling hypothesis rather than a proven mechanism of action.
What makes it notable is the unification it offers. Instead of treating epilepsy, autism, depression, and traumatic brain injury as unrelated problems requiring unrelated drugs, the review points to a single dial, cellular energy in inhibitory neurons, that light might be able to turn.
Whether that dial can be turned precisely enough to matter clinically is still an open question, and the answer will come from trials, not from wellness marketing.
