In a significant study conducted recently, findings suggest that increased exposure to artificial light at night correlates with a heightened risk of various psychiatric disorders, including anxiety, depression, bipolar disorder, PTSD, and self-harm.

In the early 1980s, I moved from a sunny country to the chilly climate of Germany, where I completed my informatics studies and began a career as an information officer in a multinational company. Despite my youthful enthusiasm and dedication, I faced challenges in both my job and building social connections, which led to fluctuations in my mood. Some attributed these difficulties to homesickness, while others suggested they stemmed from the stress of being a civilian in a demanding military environment.

Fast forward to 2010, while living in Australia during the summer, I unexpectedly found myself on a short-term consultancy project in Copenhagen during the winter. This sudden change in environment, given the opposite seasons, proved to be quite challenging.

Within a week, I noticed a marked shift in my mood, despite maintaining my usual routines for eating, exercise, and sleep. I initially attributed my sleep difficulties to jet lag and managed to cope with it using minimal melatonin supplements and an extended fasting period. However, drawing from my research on light's effects on the brain’s cognitive and emotional systems since the mid-1990s, I quickly identified the underlying issue, which I will elaborate on in the following sections.

Why are my personal experiences relevant? You may question the significance of my personal anecdotes and how they relate to this discussion. The answer is straightforward: they highlight the essential role sunlight plays in our mental health and cognitive performance, a theme I have explored in previous narratives. In this article, I intend to examine a more intricate aspect—both daytime and nighttime light exposure. Often neglected yet profoundly impactful, extensive population studies published in peer-reviewed journals have validated their importance in mental health.

Instead of diving deep into excessive scientific jargon, I will focus on the key mechanisms, effects, and implications to provide insights that empower you to use this knowledge to enhance your mental well-being.

Positive Developments from My Hometown In October 2023, an outstanding study concluded at Monash University in Melbourne, Australia, where I completed my master's degree. This institution is renowned for its global contribution to scientific research.

The research, spearheaded by Associate Professor Sean Cain from the Monash School of Psychological Sciences and the Turner Institute for Brain and Mental Health, was remarkable as it marked the largest population study to date, including 86,772 adults, and was published in Nature, one of the most prestigious peer-reviewed journals.

I will summarize the findings and key insights from this study alongside another relevant, albeit smaller-scale study from Malaysia, which was also published in Nature in August 2023. These two studies build on extensive prior research, eliminating the need for a lengthy citation list. Interested readers can refer to additional literature linked to these publicly accessible papers.

Insights from the October 2023 Paper in Nature The article titled "Day and night light exposure are associated with psychiatric disorders: an objective light study in >85,000 people" was released in Nature in October 2023. The authors indicated that disruptions to our circadian rhythms are prevalent in numerous mental health disorders. Daylight plays a crucial role in maintaining this rhythm, whereas nighttime light exposure can disrupt it.

Consequently, the amount of light we encounter daily might influence our mental health risks. The researchers analyzed data from 86,772 adults with an average age of 62.4 years, of which 57% were women. They discovered that increased light exposure at night was associated with a higher likelihood of experiencing depression, anxiety, PTSD, psychosis, bipolar disorder, and self-harm. Conversely, greater daytime light exposure appeared to reduce the risk of these conditions.

These findings remained consistent even after accounting for age, gender, physical activity, sleep quality, and overall health. Hence, the researchers concluded that avoiding nighttime light and increasing daytime light exposure could be a straightforward and effective strategy for improving mental health without the need for medication.

The complete paper is publicly available on Nature’s website. Monash University also published a report detailing key points from the lead researcher, Dr. Sean Cain. He stated that these findings could significantly impact society. Once individuals comprehend the strong influence their light exposure patterns have on their mental health, they can adopt simple strategies to enhance their well-being—specifically, obtaining bright light during the day and embracing darkness at night.

Dr. Cain expressed concern that modern lifestyles challenge our biological needs, as people spend about 90% of their time indoors under artificial lighting, which is often too dim during the day and excessively bright at night compared to natural light and dark cycles. This misalignment can confuse our bodies and negatively affect our health. The research team’s conclusions were consistent when considering factors such as shift work, sleep patterns, urban versus rural living, and cardiovascular health.

Insights from the 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. The researchers noted that limited studies have explored how various light exposure habits, such as using artificial lights during the day and screen use before bedtime, impact sleep quality and cognitive function.

They examined 301 adults from Malaysia, averaging 28 years old, who provided insights into their light exposure habits, mood, sleep quality, and cognitive abilities. Their analysis indicated that reduced use of blue light filters during the day and increased use before sleep correlated with waking up earlier. Additionally, spending more time outdoors during the day was associated with improved mood and a more consistent sleep schedule.

Conversely, mobile phone use before sleep was linked to later bedtimes, diminished energy in the morning, poorer sleep quality, and challenges with memory and focus. However, utilizing specific types of artificial lights in the morning and daytime was connected to earlier wake-up times and enhanced sleep quality.

These findings shed light on how to cultivate a healthy relationship with light to maintain well-being.

Summary of Lessons from These Two Studies on Light The first study emphasizes how both daytime and nighttime light exposure influence mental health. It suggests that excessive nighttime light may increase the likelihood of mental health issues, including depression, anxiety, and self-harm, while increased daytime light could reduce these risks.

To promote mental well-being without relying on medications, the study proposes simple lifestyle adjustments like minimizing exposure to light at night and maximizing light exposure during the day. Lead researcher Dr. Sean Cain underscores the importance of understanding these patterns and aligning light exposure with natural rhythms to avoid disrupting our biological cycles, which may positively impact mental health.

The second study's findings indicate that light exposure habits significantly influence sleep quality, mood, and cognitive functions. For instance, minimizing blue light filter usage during the day while increasing it before sleep can facilitate earlier wake-ups. Furthermore, spending more time outdoors can enhance positivity and promote a regular sleep schedule.

On the flip side, using mobile devices before bedtime may lead to later sleep times, reduced morning energy, poorer sleep quality, and difficulties with memory and concentration. These insights highlight the importance of fostering healthier relationships with light to support mental health, cognitive function, and sleep quality.

How I Improved My Mood Fluctuations in Copenhagen During the winter months in Denmark, sunlight was scarce. Although the office was brightly lit, I knew that the artificial lighting produced only about 10% of the sunlight's brightness.

Typically, natural sunlight generates about 10,000 lux. Compared to the sun, office lights emit much lower levels of blue light. Lux is a unit used to measure light intensity, which I find fascinating.

One lux is equivalent to one lumen per square meter (lm/m²), indicating the amount of visible light hitting a surface. Lux measurements are crucial in various fields, including lighting design and photography, and for assessing brightness in environments where tasks like reading or working are performed.

I sought assistance from my supervisor to find a store that sold light therapy lamps, also known as SAD lights, in Denmark and other Scandinavian countries. He provided me with the address and arranged a taxi to take me to the shop.

SAD lights are specially designed to emit bright artificial light that simulates sunlight, producing around 10,000 lux. SAD stands for Seasonal Affective Disorder, a type of depression that occurs during winter months when sunlight exposure diminishes. These lamps are utilized to treat SAD and other mood disorders by providing bright light exposure, which can help regulate circadian rhythms and improve mood and energy levels.

I bought one for approximately 50 Euros and placed it next to my computer. I had a more advanced lamp at home that cost me $500 a decade ago.

This SAD light featured two modes: one emitted warmer light, while the other was more blue-toned. I took a photo of both modes side by side to illustrate the differences.

Each morning, I spent five minutes in front of the portable light therapy lamp before starting my day. Throughout the day, I kept the lamp beside my computer in the office until I turned it off at 4 PM.

Afterward, I consciously reduced my electronic device usage, opting for a screensaver on my computer, especially between 6 and 9 PM. A screensaver designed to minimize blue light emission from devices is often termed a "blue light filter" or "night mode." Specific names for these features include "Night Shift" on Apple devices and "Night Light" on Google devices.

Additionally, I wore blue light-blocking glasses when reading from my PC, tablet, or smartphone. Within a few days of implementing these strategies, I observed a notable improvement in my mood stability and better sleep at night.

I also kept sea salt or Himalayan pink salt on my desk. Following a keto diet and intermittent fasting caused my body to lose sodium quickly, leading to mood fluctuations. A pinch of salt in my water or licking it off my finger every hour helped maintain my mood balance.

Conclusions Based on Relevant Literature A 2020 review in the Journal of Sleep Health documents that, under natural conditions, the suprachiasmatic nucleus resets daily with light exposure. However, technological advancements have caused light exposure to become misaligned with natural light-dark cycles.

The review indicates that research on jet lag and shift work shows that this desynchronization negatively impacts sleep and overall well-being.

> I elaborated on the suprachiasmatic nucleus and its role in regulating circadian rhythms in a prior article titled "Sleep Regulation: Neurobiology of the Suprachiasmatic Nucleus."

In a 2021 study titled "Bimodal effects of sunlight on major depressive disorder," researchers concluded that sunlight impacts depression both in the short and long term, but the effects are significant only during limited periods. Their data supports a pattern where short-term daily sunlight increases depression, while consistent exposure over the preceding 30 days reduces it.

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

My understanding from the literature is that a lack of sunlight does not directly cause Major Depressive Disorder; however, it can contribute to the development or worsening of depressive symptoms, particularly in individuals predisposed to Seasonal Affective Disorder (SAD). SAD is a subtype of depression that occurs seasonally, typically in winter when sunlight exposure is reduced.

A 2019 study reveals that many individuals in northern latitudes suffer from seasonal affective disorder (SAD), which arises due to diminished sunlight. The majority of those affected are women. Common symptoms include lethargy, overeating, cravings for carbohydrates, and a depressed mood. For some, SAD escalates to a depression that severely impacts daily functioning. Up to two-thirds experience depressive symptoms every winter.

Takeaways Recognize the importance of light exposure in regulating our sleep-wake cycles and overall health. As modern lifestyles increasingly misalign light exposure with natural cycles, it is vital to remain aware of the potential repercussions on sleep and mental health.

Educate yourself on the suprachiasmatic nucleus and its role in regulating circadian rhythms. Understanding the neurobiology behind sleep regulation can empower informed lifestyle choices that influence sleep patterns.

While limited sunlight exposure may exacerbate depressive symptoms, consistent exposure over the previous month has been shown to alleviate depression. Strive for a balance that meets your needs and consider integrating regular sunlight exposure into your routine.

Be aware that reduced sunlight during winter in northern latitudes can contribute to Seasonal Affective Disorder (SAD). Pay attention to common symptoms such as lethargy, carbohydrate cravings, and depressed mood, particularly in winter. Seek professional guidance 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 through healthcare providers, it's essential to recognize that not all patients respond favorably to these medications.

Consider alternative treatments, such as light therapy, cognitive-behavioral therapy, or other health-promoting lifestyle changes, to alleviate symptoms and enhance well-being.

Prioritize self-care strategies that bolster mental health and well-being, especially during periods of reduced sunlight or when facing depressive symptoms. Engage in activities that bring joy and fulfillment, ensure adequate rest, sleep soundly, practice relaxation techniques like diaphragmatic breathing, meditate, eat nutritious foods, avoid junk food, and maintain a regular exercise routine.

Remember that seeking timely social support and professional assistance is a sign of strength, and resources are available to aid in improving your mental health.

The main takeaway is to expose your eyes to bright morning sunlight to trigger the release of mood-enhancing biochemicals like serotonin, dopamine, and cortisol. Additionally, spend ample time outdoors and minimize blue light exposure at night to raise melatonin levels and safeguard your mental well-being.

Thank you for taking the time to read my insights. I wish you a healthy and fulfilling life.