Insights from a recent rigorous/large-size study indicate that increased exposure to light at night increases the risk for psychiatric disorders (anxiety, depression, bipolar, PTSD, & self-harm).

This story does not include health advice. It is for information, inspiration, and awareness purposes.

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In the early 1980s, I moved from a sun-drenched place to a freezing country to work as a civilian consultant in a military organization. Despite my youthful enthusiasm and dedication to my profession, I grappled with the job's challenges and forging social connections, experiencing mood fluctuations. While some attributed my struggles to homesickness, others pointed to the stress of navigating a military environment as a civilian in a demanding workplace.

Fast-forward three decades, I was unexpectedly assigned to a short-term consultancy project in Copenhagen during winter. Within a week, I noticed a significant change in my mood despite maintaining the same eating, exercise, and rest routines. While I experienced some difficulty with sleep, I attributed it to jet lag and managed to overcome it with minimal melatonin supplementation and an additional extended fasting period.

However, drawing from my studies on the effects of light on the brain’s cognitive and limbic systems since the mid-1990s, I quickly recognized the root cause of the issue, which I will cover in the next sections.

You might be wondering why I have shared these personal experiences and how they tie into the theme of my story. The reason is simple: emphasizing sunlight's crucial role in our mental well-being and cognitive function, as I have explored in previous stories.

However, in this story, I aim to delve into a more nuanced aspect — including both the day and night light. Often overlooked yet profoundly influential, extensive population studies in peer-reviewed journals have substantiated their nuanced significance in mental health.

Rather than delving into excessive scientific and technical intricacies, I will concentrate on the fundamental mechanisms, impacts, and implications to provide insights and empower you to leverage this knowledge to enhance your mental well-being.

In October 2023, an exceptional study was published in Nature. The study was led by Associate Professor Sean Cain, from the Monash School of Psychological Sciences and the Turner Institute for Brain and Mental Health. Dr Cain was also a lecturer at Harvard University in the US and worked as a neuroscientist at Brigham and Women’s Hospital Inc.

This study was unique because it was the first most extensive population study, including 86772 adults, and it was published in Nature, one of the most prestigious and peer-reviewed journals in the science community.

I will consolidate the findings and essential insights from the paper and another pertinent albeit smaller-scale population study conducted in Malaysia, also published in Nature in August 2023.

These two studies build upon extensive prior research, obviating the need for an exhaustive list of citations. Interested readers can access additional literature attached to these publicly available papers.

Insights from October 2023 Paper in Nature

The paper titled “Day and night light exposure are associated with psychiatric disorders: an objective light study in >85,000 people” was published in Nature in October 2023.

Researchers mentioned that disturbances in our circadian rhythm are common in many mental health conditions. Light plays a big role in this rhythm: sunlight during the day helps our body keep a healthy rhythm, while light at night can mess it up.

So, how much light we are exposed to regularly might affect our risk of having mental health problems. They looked at a large group of adults and studied how their exposure to light during the day and at night related to their mental health.

After analyzing data from 86,772 adults with an average age of 62.4 years, ± 7.4 years, 57% were women.

They found that being exposed to more light at night was linked to a higher risk of depression, anxiety, PTSD, psychosis, bipolar disorder, and self-harm. On the other hand, getting more light during the day seemed to lower the risk of these conditions.

These results were consistent even after considering factors like age, gender, physical activity, sleep quality, and overall health. So, they concluded that avoiding light at night and getting more light during the day could be a simple and helpful way to improve mental health without needing medication.

You can read the entire paper, which is publicly available on Nature’s site. Monash University also posted a report to inform the science community, extracting some points from the paper’s lead researcher, Dr Sean Cain.

Dr Cain said that their findings will have a potentially huge societal impact. Once people understand that their light exposure patterns have a powerful influence on their mental health, they can take some simple steps to optimize their well-being. It is about getting bright light in the day and darkness at night.

He thinks humans today challenge this biology, spending around 90% of the day indoors under electric lighting, which is too dim during the day and too bright at night compared to natural light and dark cycles.

As he says, it confuses our bodies and makes us unwell. His team’s findings were consistent when accounting for shiftwork, sleep, urban versus rural living, and cardio-metabolic health.

Insights from August 2023 Paper in Nature

The paper titled Light exposure behaviors predict mood, memory, and sleep quality — Scientific Reports was published in Nature in August 2023

These researchers mentioned that little research has been done on how different habits related to light exposure, like using electric lights during the day and looking at screens before bed, affect sleep quality and thinking ability.

They studied 301 adults from Malaysia, averaging 28 years old, who answered questions about their light exposure habits, mood, sleep quality, and memory and concentration.

Their analysis showed that using blue light filters less during the day and more before sleep was linked to waking up earlier. Spending more time outside during the day was associated with feeling more positive and having an earlier sleep schedule.

Using a mobile phone before sleep was linked to going to bed later, feeling less energetic in the morning, poorer sleep quality, and more trouble with memory and concentration.

On the other hand, using specific types of electric lights in the morning and daytime was linked to waking up earlier and having better sleep quality.

These findings can help us understand how to have a healthy relationship with light to stay healthy and feel good.

Summary of Lessons from These Two Studies on Light

The first story highlights how exposure to light during the day and at night can affect mental health. It suggests that having more light at night might increase the risk of mental health issues like depression, anxiety, and self-harm while getting more light during the day could potentially lower these risks.

To improve mental well-being without relying on medication, it proposes simple lifestyle changes such as reducing nighttime light exposure and increasing daytime light exposure.

Lead researcher Dr. Sean Cain emphasizes the importance of understanding these patterns and suggests aligning light exposure with natural cycles to avoid disrupting the body’s biological rhythm. This could have positive impacts on mental health.

The second paper's findings mean that light exposure habits significantly impact sleep quality, mood, and cognitive functions. For instance, using blue light filters less during the day and more before sleep can lead to waking up earlier. Spending more time outside during the day can enhance positivity and maintain a consistent sleep schedule.

On the other hand, using a mobile phone before bedtime can result in later bedtimes, feeling less energetic in the morning, poorer sleep quality, and difficulties with memory and concentration.

These insights emphasize the importance of cultivating healthier relationships with light to promote well-being and enhance sleep quality, cognitive functions, and mental health.

How did I fix my mood fluctuation in Copenhagen?

Since it was winter in Denmark, there was no sunlight during the day. The office was bright, but I knew that those lights produced perhaps only 10% of the lux from the sun.

Typically, the sun produces 10000 lux. Compared to the bright sun, office lighting emits significantly lower levels of blue light. Lux is a unit of measurement used to quantify the intensity of light. I love studying Illuminance as a hobby.

One lux equals one lumen per square meter (lm/m²). It measures the amount of visible light that falls on a surface. Lux is used in various applications, such as lighting design and photography, and to assess the brightness of environments for tasks like reading or working.

I asked my supervisor for help locating an electronic shop that sells light therapy lamps, also known as SAD lights, in Denmark and other Scandinavian nations. He gave me the address and ordered a taxi to the shop.

SAD lights are specially designed lamps that emit bright artificial light, typically mimicking sunlight, producing 10000 lux. SAD stands for Seasonal Affective Disorder, a type of depression that occurs in the winter months when sunlight exposure is reduced.

These lamps are used as treatments for Seasonal Affective Disorder and other mood disorders. They provide exposure to bright light, which can help regulate circadian rhythms and improve mood and energy levels.

I purchased one for around 50 Euros and put it next to my computer, as shown in the following photo, which has not been turned on yet. I had a better one in lamp format at home, which cost me $500 ten years ago.

This SAD light came in two modes. The first one emitted more warm lights, and the second one was more blue lights.

Upon awakening in my hotel room, I spent five minutes in front of the portable light therapy lamp before proceeding with my morning routine. Throughout the day, I positioned the lamp next to my computer in the office for several hours until turning it off at 4 PM.

After this time, I consciously minimized my electronic device usage, opting for a screen saver on my computer, especially between 6 and 9 PM. A screen saver that reduces the blue light emitted by electronic devices is commonly called a “blue light filter” or “night mode.” Some specific names for such features include “Night Shift” on Apple devices (iOS) and “Night Light” on Google devices (Android).

Additionally, I used blue light-emitting glasses when reading from my PC, tablet, or smartphone. Within a few days of adopting these practices, I noticed a significant improvement in my mood stability and experienced better nighttime sleep.

Conclusions Using Relevant Literature

As documented in this 2020 review paper in the Journal of Sleep Health, under natural conditions, the suprachiasmatic nucleus is reset daily by exposure to light. However, with technological advances, exposure to light has become desynchronized from the natural light-dark cycle.

The review paper informs that research on jet lag and the effects of shift work illustrates that this desynchronization can negatively impact sleep and overall well-being.

I explained the details of the suprachiasmatic nucleus and how the brain regulates circadian rhythms in a recent story titled Sleep Regulation: Neurobiology of the Suprachiasmatic Nucleus.

In a 2021 paper titled “Bimodal effects of sunlight on major depressive disorder,” researchers concluded that “the effect of sunlight on depression appears in both the short and long terms, but the effect is significant only for limited periods. The data examined in this study supports a pattern where short-term daily sunlight increases depression, and daily sunlight for the previous 30 days decreases depression.”

As documented in this paper,

“Major depressive disorder is a common psychiatric disorder associated with marked suffering, morbidity, mortality, and cost. The World Health Organization projects that by 2030, major depression will be the leading cause of disease burden worldwide. While numerous treatments for major depression exist, many patients do not respond adequately to traditional antidepressants.”

My understanding from the overall literature is that the lack of sunlight alone does not directly cause Major Depressive Disorder, but it can contribute to the development or exacerbation of depressive symptoms, particularly in specific people susceptible to Seasonal Affective Disorder (SAD). SAD is a subtype of depression that occurs seasonally, typically during winter when there is less natural sunlight exposure.

As documented in this 2019 paper, “

Many people in northern latitudes suffer from seasonal affective disorder (SAD), which occurs as a reaction to reduced sunlight. Three‐quarters of those affected are women. Lethargy, overeating, craving for carbohydrates, and depressed mood are common symptoms. In some people, SAD becomes a depression that seriously affects their daily lives. Up to two‐thirds experience depressive symptoms every winter.”

Takeaways

Recognize that exposure to light is crucial in regulating our sleep-wake cycle and overall well-being. As modern lifestyles increasingly desynchronize light exposure from natural cycles, it is essential to be mindful of the potential consequences on sleep and mental health.

Educate yourself about the suprachiasmatic nucleus and how the brain regulates circadian rhythms. Understanding the neurobiology behind sleep regulation can empower us to make informed lifestyle choices that may affect our sleep patterns.

While limited daily exposure to sunlight may increase depressive symptoms, consistent exposure over the previous 30 days has been shown to decrease depression. Find a balance that suits your needs, and consider incorporating regular exposure to natural sunlight into your routine.

Understand that reduced sunlight exposure during winter in northern latitudes can contribute to Seasonal Affective Disorder (SAD). Be mindful of common symptoms like lethargy, overeating, carbohydrate cravings, and depressed mood, especially during the winter months. Seek professional help if you suspect you may be experiencing symptoms of SAD or depression.

Explore various treatment options for major depressive disorder and SAD. While traditional antidepressants are available by doctors, it is necessary to recognize that not all patients respond adequately to these medications.

Consider alternative treatments like light therapy, cognitive-behavioral therapy, or other health-inducing lifestyle modifications to eliminate symptoms and improve well-being.

Prioritize self-care practices that support mental health and well-being, particularly during times of reduced sunlight exposure or when experiencing depressive symptoms.

Participate in activities that bring joy and fulfillment, rest, sleep well, practice relaxation techniques like diagrammatic breathing, meditate, eat healthy foods, refrain from junk foods, and exercise regularly.

Remember that seeking timely social support and professional help is a sign of strength, and resources are available to help you improve your mental health.

The key takeaway is exposing our eyes to bright sunlight in the morning to trigger the release of mood-enhancing biochemicals like serotonin, dopamine, and cortisol. Additionally, spending ample time outdoors and minimizing exposure to blue light at night are essential to increase melatonin levels and preserve our mental well-being.

Thank you for reading my perspectives. I wish you a healthy and happy life.

If you found this story helpful, you may also check out my other articles on NewsBreak. As a postdoctoral researcher and executive consultant, I write about important life lessons based on my decades of research and experience in cognitive, metabolic, and mental health.