In the world of modern wellness, we often spend hundreds on supplements, health related subscriptions, and expensive technology to optimize our physical and mental well-being. Although those items can be useful, we tend to forget about simpler tools that are foundational to how we feel, and how productive we are. One of those simple tools is light! More specifically our relationship with its presence and absence.
Light exposure is heavily interconnected with our physiology. Almost every cell and organ in our body functions based on a natural 24-hr clock, this is known as our circadian rhythm. One example of how the circadian rhythm works is our sleep and wake schedule. We have specific cells in the back of our eyes called the photosensitive retinal ganglion cells. These cells absorb the photons of light that is in our environment, and through other neural pathways communicate with a structure in our brain called the Suprachiasmatic Nucleus (SCN). SCN has direct pathways to areas in our body that cause the release of hormones such as melatonin and cortisol, which are responsible for many things including our feelings of sleepiness and alertness (Rahman SA, 2019). That is why our relationship with light is so foundational for mental and physical well-being.
Effects on Sleep Timing and Sleep Quality
Our circadian rhythm gets cues from the environment such as light exposure, physical activity, and mealtimes. These cues are known as zeitgebers (literally translates to “Time-Giver), and they regulate when we naturally fall asleep and wake up. The dominant zeitgeber in humans is light (Facer-Childs, 2019).
Researchers from the University of Birmingham, experimented with people considered night owls who were struggling with sleep deprivation, and poor cognitive performance. The experimental group was instructed to view natural light during a walk outside for a minimum of 10 mins on sunny days, and 20 mins on forecast days, within the first hour of awakening. They were also given fixed times for meals, exercise, and sleep. By the end of the experiment (which was around five weeks) the participants were able to naturally wake up and go to bed two hours earlier than their usual time, without impacting their quality of sleep (Facer-Childs, 2019).
Thus, if you’re suffering from a chaotic sleep schedule, or jet lag, to get yourself back on track consider waking up at the desired time and within the first hour of waking up going on a 10-to-20-minute walk outside where you are exposed to natural light. It’s also worth mentioning that the researchers also examined the participants cognitive and physical performance 8 hours after getting up. They found that participants were the least alert 8 hours after waking up. After the interventions the experimental group showed significant improvement in their cognitive and physical performance in the tests given after that 8-hour mark. It is unlikely that viewing bright light is the sole causal reason for this improvement, however it is likely to be a significant contributing factor (Facer-Childs, 2019).
Impacts of light on hormone fluctuations (Melatonin, and Cortisol) and sleep quality
Hormones are chemicals that are produced by our body and released into the bloodstream, they act as messengers, telling tissues and organs what to do. These messengers help our body control important things. For example, melatonin is a hormone that is associated with us feeling sleepy, and cortisol is associated with feelings of alertness. This matters because levels of melatonin in our body help us sleep better.
As mentioned earlier our relationship to both presence and absence of light is very important. In an analysis where researchers were interested in determining how bright light exposure at night impacts the levels of melatonin in participants. They randomly assigned and exposed participants to three different conditions of light at night. One being Continuous Bright Light, in which participants were exposed to ambient bright light for 6.5 hours through the night. The other condition was Intermittent Bright light in which participants were exposed to 15 mins of ambient bright light followed by an hour of dim light. And lastly the control group which was exposed to dim light for the entire night (Rahman SA, 2019).
Participants in Continuous Bright Light experienced continuous suppression of their melatonin levels throughout the entire time of the light exposure. And even more surprisingly, in the Intermittent Bright light condition the researchers found that only 15 mins of bright light exposure suppressed melatonin levels by around 40% compared to baseline, and after an hour of low dim light the melatonin levels recovered only by 50% (Rahman SA, 2019). This paper shows that even short periods of light exposure at nighttime can have detrimental effects on our melatonin levels, and therefore quality of sleep. So, if you’d like to sleep better at night and feel more refreshed in the morning try to avoid light exposure during sleeping. Keep your room as dark as possible when you sleep: turn off the light on your monitors and clocks.
The Role of Light and Mental Well Being
It’s no surprise that consistent and higher quality sleep will positively impact our mental well-being, but did you know that light therapy is also clinically used as a source of non-pharmacological treatment for treating a variety of mental health disorders!
In a review done by the American Journal of Psychiatry, a group of psychiatrists and psychologists reviewed the efficacy of light therapy in treatment of mood disorder for adult patients. After following a very strict inclusion criteria for the reviews they discussed, they found that the majority of studies showed significant relationships between the treatment and reduction in symptoms of the disorders (Golden RN, 2005).
Conclusion
It’s clear that our relationship with light is crucial to our overall well-being. All the way from sleep quality to cognitive and physical performance, and finally our mental well-being. So, if you’re after a zero-cost method to boost your health and mood, try soaking up some bright natural light in the mornings by going outside for a minimum of 15 mins on sunny days, and 30 mins on forecast days, and try your best to dial it way down an hour before bed. However, please be warned that too much exposure to bright light can lead to eye strain, headaches, damage to your skin, and other health consequences. So please do not overdo it by standing in the sun for hours at a time (Yale Psychiatry, 2024). Embrace the brightness, but don’t overexpose yourself.
Written by Alireza Taeb and edited by Aldrin V. Gomes, Ph.D.
References
1) Facer-Childs ER, Middleton B, Skene DJ, Bagshaw AP. Resetting the late timing of 'night owls' has a positive impact on mental health and performance. Sleep Med. 2019 Aug;60:236-247. doi: 10.1016/j.sleep.2019.05.001. PMID: 31202686.
2) Rahman SA, Wright KP Jr, Lockley SW, Czeisler CA, Gronfier C. Characterizing the temporal Dynamics of Melatonin and Cortisol Changes in Response to Nocturnal Light Exposure. Sci Rep. 2019 Dec 23;9(1):19720. doi: 10.1038/s41598-019-54806-7. PMID: 31873098.
3) Golden RN, Gaynes BN, Ekstrom RD, Hamer RM, Jacobsen FM, Suppes T, Wisner KL, Nemeroff CB. The efficacy of light therapy in the treatment of mood disorders: a review and meta-analysis of the evidence. Am J Psychiatry. 2005 Apr;162(4):656-62. doi: 10.1176/appi.ajp.162.4.656. PMID: 15800134.
4) Leproult R, Colecchia EF, L'Hermite-Balériaux M, Van Cauter E. Transition from dim to bright light in the morning induces an immediate elevation of cortisol levels. J Clin Endocrinol Metab. 2001 Jan;86(1):151-7. doi: 10.1210/jcem.86.1.7102. PMID: 11231993.
5) Department of Psychiatry. “What Are the Risks of Light Treatment?” Psychiatry, 2024, medicine.yale.edu/psychiatry/research/programs/clinical-people/winter/risks/.
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