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Michael Cleary-Gaffney: The Dark Side Of Light

Everyday when the night-time falls we illuminate our rooms with artificial light in order to carry out our work and our street become illuminated to allow us safely navigate our streets. Although, our ability to manipulate and prolong the longevity of our light-time period has significant advantages it comes with possible health consequences. Significant amount of research has found that this manipulation of our light/dark cycle  interferes with our internal timing system which was typically aligned to natural day/night. As I discussed in my previous blog when interference to the circadian clock occurs this has a knock-on effect to the timing of other cells in the body.

The negative effects of lighting come from shift workers. Shift workers are individuals who are exposed to large amounts of artificial light when natural darkness has fallen. Evidence from nurses who work night shifts report feeling of hopelessness (symptom of depression) within three months of working night-shifts. Those that have worked over 20 years in nursing have a significantly higher chance of being diagnosed with clinical depression. This illustrates the negative consequences of artificial light during periods of natural darkness.

However, what about the effects of dim light-at-night? Each night before we go to sleep our rooms our illuminated with LED emitting alarm clocks, our bedrooms are illuminated from outside urban lighting and some of us sleep with the television on. My work questions can this dim-light which the vast majority of us are exposed to interfere with our circadian clock and induce depressive behaviours. Some other labs have investigated this topic and have found that indeed dim light-at-night has the power to interfere with our circadian rhythms and in induce depressive-like behaviours along with causing molecular changes within the brain. This would suggest that paradoxically there is a dark side to light.

For those interested on reading more on this topic see: Bedrosian, T. A., & Nelson, R. J. (2013). Influence of the modern light environment. Molecular Psychiatry, 18, 751-757.

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