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The Influence of Light Wavelength on Human HPA Axis Rhythms: A Systematic Review
Isabella Robertson-Dixon1, Melanie J Murphy1, Sheila G Crewther1,2
1Department of Psychology, Counselling and Therapy, La Trobe University, Melbourne, VIC 3086, Australia.
Life (Basel, Switzerland)
|October 28, 2023
Summary
Bright light exposure, especially with blue/green wavelengths during late night or early morning, significantly increases cortisol. Light
Area of Science:
- Chronobiology
- Neuroendocrinology
- Vision Science
Background:
- Environmental light synchronizes circadian rhythms, influencing sleep and hormone secretion.
- The suprachiasmatic nucleus (SCN) integrates light information via intrinsically photosensitive retinal ganglion cells.
- While light's effect on melatonin is known, its impact on cortisol rhythms is less understood.
Purpose of the Study:
- To systematically review the effects of light spectral power distribution and intensity on cortisol levels in healthy individuals.
- To clarify how daytime light exposure influences cortisol secretion patterns.
- To assess the sensitivity of cortisol regulation to light characteristics.
Main Methods:
- Systematic literature search across multiple databases (PubMed, Web of Science, etc.) up to June 2023.
- Inclusion criteria focused on studies investigating light parameters and cortisol levels in healthy participants.
- Analysis of 12 selected studies involving 337 participants.
Main Results:
- Bright light exposure, irrespective of color, during late night/early morning significantly elevates cortisol compared to dim light.
- Early morning exposure to bright light with stronger short-wavelength (blue/green) components induced greater cortisol increases than long-wavelength (red) light.
- Cortisol circadian regulation is demonstrably sensitive to light's wavelength composition.
Conclusions:
- Environmental light's spectral characteristics influence cortisol rhythms, similar to melatonin.
- Wavelength optimization and reporting are crucial for light intervention studies on cortisol and HPA axis function.
- Careful consideration of short-wavelength light exposure is needed in artificial environments during sensitive circadian phases.
Keywords:
HPA axiscircadian rhythmcortisolhypothalamic pituitary adrenal axisspectrumstresswavelengthMore Related Videos
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