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Light flash therapy in the wild

Nature Reviews Psychology volume 1, page 437 (2022)Cite this article

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Phototherapy (controlled application of artificial or natural light) is the first-line treatment for circadian and seasonal affective disorders. Like a drug, light can elicit physiological responses (besides vision) when received by receptors in the human eye. For example, as early as the 1980s, it was discovered that bright light can reduce and alter the timing of melatonin production in humans. These findings suggested that light exposure in the morning or evening can shift circadian rhythms earlier or later, respectively.

The critical neural mediators that underlie these phenomena (intrinsically photosensitive retinal ganglion cells) were identified 20 years later. These cells are maximally sensitive to short-wavelength light and project directly to the ‘circadian master clock’ in the suprachiasmatic nucleus. Primarily guided by light–dark cues, this clock synchronizes circadian rhythms to the external environment and influences sleep–wake timing by promoting wakefulness or sleepiness. In 2016, a ‘loophole’ in the light processing circuitry was discovered: short intermittent light flashes — unlikely to occur naturally — evoke more substantial circadian shifts than continuous light in the laboratory.

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References

Original article

  • Kaplan, K. A. et al. Effect of light flashes vs sham therapy during sleep with adjunct cognitive behavioral therapy on sleep quality among adolescents: a randomized clinical trial. JAMA Netw. Open 2, e1911944 (2019)

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  • Provencio, I. et al. A novel human opsin in the inner retina. J. Neurosci. 20, 600–605 (2000)

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  • Najjar, R. P. & Zeitzer, J. M. Temporal integration of light flashes by the human circadian system. J. Clin. Invest. 126, 938–947 (2016)

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Authors and Affiliations

  1. Centre for Chronobiology, Psychiatric Hospital of the University of Basel, Basel, Switzerland

    Rafael Lazar

  2. Transfaculty Research Platform Molecular and Cognitive Neurosciences, University of Basel, Basel, Switzerland

    Rafael Lazar

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  1. Rafael Lazar
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Correspondence to Rafael Lazar.

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The author declares no competing interests.

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Lazar, R. Light flash therapy in the wild. Nat Rev Psychol 1, 437 (2022). https://doi.org/10.1038/s44159-022-00084-6

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  • DOI: https://doi.org/10.1038/s44159-022-00084-6

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