Light Therapy Increases Brain Connectivity Following Injury
Low-level light therapy has been studied for years for its wound-healing properties. Researchers at Massachusetts General Hospital (MGH) conducted a study on the effects of low-level light therapy on patients who suffered moderate traumatic brain injury. The study, published in Radiology, a journal of the Radiological Society of North America (RSNA), found that light therapy increases brain connectivity in patients with traumatic brain injury.
How Light Therapy Works
Lights of different wavelengths have been studied for their wound-healing properties. In this study, researchers used a helmet that emits near-infrared light to treat patients. “The skull is quite transparent to near-infrared light,” said study co-lead author Rajiv Gupta, M.D., Ph.D., from the Department of Radiology at MGH. “Once you put the helmet on, your whole brain is bathing in this light.”
The Study
The researchers used functional MRI to gauge the effects of the light therapy. They focused on the brain’s resting-state functional connectivity, the communication between brain regions that occurs when a person is at rest and not engaged in a specific task. The researchers compared MRI results during three recovery phases: the acute phase of within one week after injury, the subacute phase of two to three weeks post-injury, and the late-subacute phase of three months after injury.
Of the 38 patients in the trial, 21 did not receive light therapy while wearing the helmet. This was done to serve as a control to minimize bias due to patient characteristics and to avoid potential placebo effects.
The Results
Patients who received low-level light therapy showed a greater change in resting-state connectivity in seven brain region pairs during the acute-to-subacute recovery phase compared to the control participants. “There was increased connectivity in those receiving light treatment, primarily within the first two weeks,” said study coauthor Nathaniel Mercaldo, Ph.D., a statistician with MGH. “We were unable to detect differences in connectivity between the two treatment groups long term, so although the treatment appears to increase the brain connectivity initially, its long-term effects are still to be determined.”
Brain connectivity increased in patients receiving light therapy
The Mechanism Behind Light Therapy
The precise mechanism of the light therapy’s effects on the brain is still to be determined. Previous research points to the alteration of an enzyme in the cell’s mitochondria, leading to more production of adenosine triphosphate, a molecule that stores and transfers energy in the cells. Light therapy has also been linked with blood vessel dilation and anti-inflammatory effects.
The Future of Light Therapy
While connectivity increased for the light therapy-treated patients during the acute to subacute phases, there was no evidence of a difference in clinical outcomes between the treated and control participants. Additional studies with larger cohorts of patients and correlative imaging beyond three months may help determine the therapeutic role of light in traumatic brain injury.
The researchers expect the role of light therapy to expand as more study results come in. The 810-nanometer-wavelength light used in the study is already employed in various therapeutic applications. It’s safe, easy to administer, and does not require surgery or medications. The helmet’s portability means it can be delivered in settings outside of the hospital. It may have applications in treating many other neurological conditions, according to Dr. Gupta.
“There are lots of disorders of connectivity, mostly in psychiatry, where this intervention may have a role,” he said. “PTSD, depression, autism: these are all promising areas for light therapy.”
