Artificial light at night and risk of mental disorders

Artificial lights can also be dangerous for human beings, even with regard to mental partologies

by Lorenzo Ciotti
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Artificial light at night and risk of mental disorders

Among the environmental damages caused by light pollution, there is difficulty or loss of orientation in various animal species, alteration of the photoperiod in some plants, alteration of the circadian rhythms in plants, animals and microorganisms, stunted growth of the periphyton.

In 2001, a new retinal photoreceptor was discovered in the eye which does not contribute to the mechanism of vision, but regulates our biological clock. The peak sensitivity of this sensor is in the blue part of the visible spectrum and for this reason, lamps with a strong blue cast are the ones that can most alter our circadian rhythms.

While the lamps that cause less damage, from this point of view, since they have a dominant red color of the visible spectrum, are the high pressure sodium ones, and even less harmful, the low pressure ones. Artificial lights can also be dangerous for human beings, even with regard to mental partologies.

The study Artificial light at night and risk of mental disorders: A systematic review, published on the The Science of the total environment, said us: "Emerging evidence suggests a possible association between artificial light at night (LAN) exposure and physiological and behavioral changes, with implications on mood and mental health.

Due to the increased amount of individuals' LAN exposure, concerns have been raised regarding harmful impact of light pollution on mental health at the population level. To perform a systematic review of observational studies to investigate if light at night, assessed both indoor and outdoor, may be associated with an increased risk of mental diseases in humans.
We reviewed the epidemiological evidence on the association between LAN exposure, assessed either via satellite photometry or via measurements of bedroom brightness, and mental disorders.

We systematically searched the PubMed, Embase and Web of Science databases up to April 1, 2022. Studies were included if they assessed the link between indoor or outdoor artificial light at night and one or more mental disorders in human populations.

Nine eligible studies were included in this review: six studies had a cross-sectional design, two had a longitudinal design with a median follow-up of 24 months, and one was a case-cohort study. Overall, we found moderate evidence of a positive association between LAN exposure and depressive symptoms and to a lesser extent other mental disorders, though the number of studies was limited and potential residual confounding such as socioeconomic factors, noise, or air pollution may have influenced the results.

Although more robust evidence is needed, the epidemiological evidence produced so far seems to support an association between LAN and risk of depressive disorders."