While it may have felt freeing for some people to forego their usually hectic schedules at the start of the COVID-19 pandemic, the lockdowns and stay-at-home orders may have contributed to the phenomenon of “coronasomnia,” or sleep problems — particularly insomnia.
One possible explanation: Prolonged lockdowns are associated with insufficient sunlight, or limited exposure to any natural light. Although coronasomnia was often attributed to stress and anxiety, the disruption of light-based cues due to home confinement also played a role in shifting people’s circadian rhythms. UCLA’s Sleep Disorders Center reported a 20 to 30 percent rise in complaints of insomnia in the early stretch of the pandemic, aligning with data from China and France. Insomnia can in turn impair productivity, mood and physical health. But getting enough natural light can improve both sleep quality and a wide range of health outcomes.
For one, sunlight is important in regulating mood. A 2021 Journal of Affective Disorders study analyzed the connection between exposure to outdoor light and the risk of depression by assessing the outcomes of over 400,000 participants from the U.K. Biobank Study.
“These people reported the typical amount of time they [spent] in outdoor light and we found that the more light people got, the less risk they had for developing major depressive disorder and [using] antidepressants,” says study author Sean W. Cain, who leads the Sleep Program at Australia’s Turner Institute for Brain and Mental Health. “We think that the light strengthened the internal clock.”
More broadly, light exposure is absolutely critical in regulating the body’s circadian rhythms, which the NIH defines as physical, behavioral and mental changes that run on a 24-hour cycle. The central brain clock in the hypothalamus receives light input through the eyes, which drives and coordinates rhythms throughout the body, says Ilia Karatsoreos, associate professor of psychological and brain sciences at the University of Massachusetts Amherst.
It also sends information to the various clocks found in nearly every cell, including those found in the areas of the brain that are critical for mood, sleep regulation and cognition, along with various tissues that drive different day and night functions.
“By changing the quantity, quality, and timing of light, the function of this clock can be degraded or augmented,” says Karatsoreos. “If we change how the clock works, then it can have significant effects throughout this complex web of ‘biological timing’ organization.” . . . (read more)