In recent research, it has been discovered that prolonged exposure to artificial light during nighttime can elevate the likelihood of developing psychiatric disorders such as anxiety, depression, bipolar disorder, PTSD, and self-harming behavior.

In the early 1980s, I relocated from a sunny country to Germany, where I pursued my degree in informatics and later became an information officer for a global organization. Despite my enthusiasm, I faced challenges in my career and social life, leading to fluctuations in my mood. While some attributed these changes to homesickness, others suggested that the stress of adapting to a military setting as a civilian played a role.

Fast forward to 2010, while living in Australia, I was assigned to a consultancy project in Copenhagen during winter. This abrupt seasonal transition proved challenging. Within days, I noticed a decline in my mood, although I maintained my usual eating, exercise, and sleeping habits. Initially, I blamed it on jet lag, managing it with minimal melatonin and an extended fasting routine.

Drawing from my studies on light's influence on cognitive and emotional processes, I soon identified the real issue, which I will elaborate on further.

Why is this relevant? You might question why I share these personal anecdotes. The answer lies in underscoring the critical role sunlight plays in our mental and cognitive health, a theme I have addressed in previous articles. This time, I aim to explore a more intricate aspect — the effects of both daytime and nighttime light exposure, which are often overlooked yet hold significant implications for mental health.

Instead of diving into overly technical details, I will focus on the essential mechanisms, impacts, and potential applications of this knowledge to help improve your mental well-being.

Uplifting Research Developments from My Alma Mater In October 2023, a groundbreaking study was completed at Monash University in Melbourne, Australia, where I earned my master's degree. This institution has made substantial contributions to scientific research.

The study, led by Associate Professor Sean Cain from the Monash School of Psychological Sciences and the Turner Institute for Brain and Mental Health, analyzed a substantial sample of 86,772 adults. It was published in Nature, a highly respected peer-reviewed journal in the scientific community.

I will summarize the findings and key insights from this study alongside another smaller-scale research project conducted in Malaysia, published in Nature in August 2023. Together, these studies build on extensive prior research, eliminating the need for an exhaustive citation list. Interested readers can explore additional literature linked to these publicly available articles.

Insights from the October 2023 Nature Study The research paper titled “Day and night light exposure are associated with psychiatric disorders: an objective light study in >85,000 people” highlights the relationship between light exposure and mental health. The study reveals that circadian rhythm disruptions are prevalent in various mental health conditions. Natural light during the day helps maintain a healthy rhythm, while nighttime light exposure can disrupt it.

The researchers investigated how regular exposure to light correlates with mental health outcomes. Their analysis of 86,772 adults, with an average age of 62.4 years (57% female), revealed a concerning link: increased nighttime light exposure correlated with higher risks of depression, anxiety, PTSD, psychosis, bipolar disorder, and self-harming behaviors. Conversely, greater daytime light exposure appeared to decrease the risk of these conditions.

These conclusions remained valid even after controlling for factors like age, gender, physical activity, sleep quality, and overall health. Thus, the researchers suggested that avoiding nighttime light while increasing daytime exposure could be a straightforward yet effective approach to enhancing mental health without medication.

The entire study is accessible on Nature's website, with additional insights provided by Monash University, including comments from lead researcher Dr. Sean Cain. He expressed that understanding the impact of light exposure on mental health could lead to significant societal changes, emphasizing the importance of bright light during the day and darkness at night.

Dr. Cain pointed out that modern lifestyles often conflict with our biological needs, with individuals spending around 90% of their day indoors under artificial lighting that is too dim during the day and overly bright at night. This disruption can lead to health issues. His team found consistent results when accounting for factors like shift work, urban versus rural living, and overall health conditions.

Insights from the August 2023 Nature Study The August 2023 study titled “Light exposure behaviors predict mood, memory, and sleep quality” examined how light exposure habits, such as daytime electric lighting use and screen time before bed, influence sleep quality and cognitive functions.

The researchers surveyed 301 Malaysian adults, averaging 28 years old, who provided insights into their light exposure habits, mood, sleep quality, and cognitive performance. Their findings indicated that reduced blue light filter usage during the day and increased use before sleep led to earlier wake times. More time spent outdoors during the day correlated with improved mood and a more consistent sleep schedule.

Conversely, using mobile devices before bedtime resulted in later sleep times, decreased morning energy, poorer sleep quality, and cognitive difficulties. However, utilizing certain types of electric lighting during the day was linked to earlier wake times and better sleep quality.

These findings contribute to our understanding of how to maintain a healthy relationship with light for overall well-being.

Summary of Key Lessons from Both Studies The first study emphasizes that light exposure, both during the day and at night, significantly impacts mental health. Increased nighttime light exposure is associated with a higher risk of depression, anxiety, and self-harming behaviors, while enhanced daytime light exposure could mitigate these risks.

To improve mental well-being without relying on medication, simple lifestyle adjustments such as reducing nighttime light exposure and increasing daylight exposure are recommended. Dr. Sean Cain stresses the importance of aligning light exposure with natural rhythms to support mental health.

The second study's findings suggest that light exposure habits profoundly influence mood, sleep quality, and cognitive abilities. For example, minimizing blue light filter usage during the day and increasing it before sleep can lead to earlier wake times, while more outdoor time correlates with improved mood and consistent sleep patterns.

Conversely, device use before bedtime can disrupt sleep schedules and impair cognitive functions. These insights highlight the significance of fostering healthier light exposure habits to enhance mental health and overall well-being.

How I Stabilized My Mood in Copenhagen During winter in Denmark, the lack of sunlight posed a significant challenge. Although the office was well-lit, I realized the artificial lights emitted only about 10% of the sunlight's lux levels. Typically, sunlight provides around 10,000 lux.

In my quest for a solution, I sought assistance from my supervisor in finding light therapy lamps, known as SAD lights, which are designed to mimic sunlight and produce 10,000 lux. These lamps are used to treat Seasonal Affective Disorder, a type of depression that occurs during winter months when sunlight exposure is limited.

After purchasing a lamp for approximately 50 Euros, I placed it next to my computer. I also owned a more advanced model at home, which I had bought for $500 a decade earlier.

This SAD light offered two modes: one with warmer light and another with a bluer hue. I documented each mode's appearance side by side.

Every morning, I spent five minutes in front of the light therapy lamp before starting my day. I kept the lamp beside my computer for several hours until turning it off at 4 PM. Afterward, I consciously reduced my electronic device usage, activating a blue light filter on my computer between 6 and 9 PM.

I also wore blue light-blocking glasses while using my devices. Within a few days, I noticed a substantial improvement in my mood and sleep quality.

To support my well-being, I kept sea salt or Himalayan pink salt on my desk, as my keto diet led to rapid sodium loss, causing mood fluctuations. A pinch of salt in my water or on my finger every hour helped maintain my mood stability.

Conclusions from Relevant Literature A 2020 review in the Journal of Sleep Health highlights that, under natural conditions, the suprachiasmatic nucleus resets daily through light exposure. However, modern advancements have caused a desynchronization from natural light-dark cycles.

Research on jet lag and shift work indicates that this desynchronization can adversely affect sleep and overall well-being.

In a 2021 study titled “Bimodal effects of sunlight on major depressive disorder,” researchers concluded that sunlight impacts depression both short and long-term. However, the effects vary by duration, with daily exposure over 30 days significantly reducing depressive symptoms.

The literature suggests that while lack of sunlight does not directly cause Major Depressive Disorder, it can exacerbate symptoms in individuals susceptible to Seasonal Affective Disorder (SAD), which is prevalent in regions with reduced sunlight during winter months.

Takeaways Recognize the importance of light exposure in regulating sleep-wake cycles and overall health. As modern lifestyles often disrupt natural light exposure, it’s crucial to be aware of the potential effects on mental health.

Educate yourself on the suprachiasmatic nucleus and how it regulates circadian rhythms to make informed lifestyle choices. While limited sunlight exposure can increase depressive symptoms, consistent exposure over the previous month has been shown to decrease them.

Be aware that reduced sunlight during winter can contribute to SAD. Recognize common symptoms, and seek professional help if needed. Explore treatment options for major depressive disorder and SAD, including light therapy and lifestyle modifications.

Prioritize self-care practices that enhance mental health, especially during periods of reduced sunlight. Engage in fulfilling activities, maintain healthy eating habits, exercise regularly, and seek social support when necessary.

The key takeaway is to expose your eyes to bright sunlight in the morning to stimulate the release of mood-enhancing biochemicals. Furthermore, spending time outdoors and reducing blue light exposure at night is crucial for preserving mental well-being.

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