Introduction

Blue light from computers, smartphones, and TV screens is often thought to be harmful to people. However, according to research from the University of Arizona done in 2020, early morning blue light exposure therapy can aid the healing process of people impacted by mild traumatic brain injury. "When it comes to light, timing is critical. Light is not necessarily good or bad in-and-of-itself," said William D. "Scott" Killgore, psychiatry professor in the College of Medicine -- Tucson.

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Benefits of exposure to blue light

Daily exposure to blue light each morning helps retain the circadian rhythm and thus improve sleep quality. However, it has also been proved to help people to recover from mild traumatic brain injury (mTBI), or concussion. "That improvement in sleep was translated into improvements in cognitive function, reduced daytime sleepiness and actual brain repair," said Killgore.

 

The study

In this study, a placebo-controlled trial of 32 adults with a recent mTBI was performed. Participants were treated with 6-weeks of daily 30-min pulses of blue light or amber placebo light each morning. The scientists compared the neurocognitive and neuroimaging outcomes, including gray matter volume (GMV), resting-state functional connectivity, directed connectivity using Granger causality, and white matter integrity using diffusion tensor imaging (DTI) of the participants with different treatments.

 

Results

Relative to placebo*, the participants treated with blue light fell asleep and woke an average of one hour earlier than before the trial and were less sleepy during the daytime. They also showed improvement in their speed and efficiency in brain processing as well as cognition. 

 

In general, morning blue light led to phase-advanced sleep timing, reduced daytime sleepiness, and improved executive functioning, and was associated with increased volume of the posterior thalamus, greater thalamo-cortical functional connectivity, and increased axonal integrity of these pathways.  

 

Their findings provide insight into the contributions of the circadian and sleep systems in brain repair and lay the groundwork for interventions targeting the retinohypothalamic system to facilitate injury recovery.

 

The science behind the phenomenon presented in the clinical trial is that "blue light suppresses brain production of a chemical called melatonin," Killgore said. "You don't want melatonin in the morning because it makes you drowsy and prepares the brain to sleep. When you are exposed to blue light in the morning, it shifts your brain's biological clock so that in the evening, your melatonin will kick in earlier and help you to fall asleep and stay asleep."

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*Placebo: a fake medical treatment that does not contain an active substance meant to affect health. It is often used in clinical trials so that the group that receives a placebo thinks it is the real drug.

 

References:

Killgore, William D. S., et al. “A Randomized, Double-Blind, Placebo-Controlled Trial of Blue Wavelength Light Exposure on Sleep and Recovery of Brain Structure, Function, and Cognition Following Mild Traumatic Brain Injury.” Neurobiology of Disease, vol. 134, 2020, p. 104679. Crossref, doi:10.1016/j.nbd.2019.104679.

 

“Blue Light Can Help Heal Mild Traumatic Brain Injury.” ScienceDaily, 15 Jan. 2020, www.sciencedaily.com/releases/2020/01/200115164017.htm.

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Image: “Blue Light and Your Brain.” Spektrum Glasses, 14 Oct. 2016, www.spektrumglasses.com/blogs/news/blue-light-and-your-brain.

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Resources by Judy Zhu