Circadian Lighting: Illuminating Solutions for Seasonal Depression

As the rhythm of daylight shifts with the seasons, our mood and energy levels often follow suit. In this article we look into circadian lighting, a forward-thinking solution designed to counteract the adverse effects of reduced natural light, particularly during shorter days, by aligning indoor lighting with our body’s inherent rhythms to support mental and physical well-being.

Table of Contents:

1. Introduction to Circadian Lighting
2. The Science Behind Circadian Lighting
3. Circadian Lighting and Seasonal Depression
4. Implementing Circadian Lighting at Home and Work
5. Case Studies and Success Stories
6. Challenges and Considerations
7. Future of Circadian Lighting
8. Conclusion

Experience the harmony of circadian lighting in a modern hallway, where smart lighting solutions bring the benefits of natural daylight indoors. Image courtesy of Hang Niu

1. Introduction to Circadian Lighting

Circadian lighting, an innovative approach that harmonizes indoor lighting with our body’s natural rhythms, is transforming how we light our spaces. Central to this concept are circadian rhythms, internal clocks that govern our sleep-wake cycle, influenced significantly by light. Properly timed light exposure can energize us during the day and promote rest at night. Circadian lighting systems, therefore, aim to replicate the pattern of natural light, adjusting in color and intensity throughout the day to support our psychological and physiological well-being. This integration of light with our biological needs not only enhances mood and productivity but also holds the potential to alleviate symptoms of seasonal depression, making it a vital consideration in modern lighting design.

2. The Science Behind Circadian Lighting

Circadian lighting systems mimic the natural light cycle, playing a crucial role in synchronizing our internal biological clocks. These systems capitalize on our knowledge of the eye’s light-sensitive cells, known as intrinsically photosensitive retinal ganglion cells (ipRGCs). These cells are key in regulating our circadian rhythms, even in the absence of vision (blind people who still have the eyeballs). It turns out that this is the only way by which circadian rhythm is set on daily basis. This includes the regulation of sleep patterns and hormone production, which are vital for both our physical and mental well-being.

The concept of circadian lighting underscores our inherent biological link to sunlight, essential for the regulation of our internal clocks. These specialized receptors in our eyes can detect daylight and signal our brains to synchronize with the natural day-night cycle, influencing crucial aspects like sleep and alertness. By mimicking natural daylight indoors, circadian lighting systems aim to preserve the natural rhythm our bodies are designed to follow, thus supporting our mental and physical health.

For those interested in further exploring the neurobiology behind resetting our internal clock daily, the Huberman Lab offers an insightful video. It presents a comprehensive toolkit of behavioral and supplement-based strategies tailored to improve sleep quality, duration, and its overall impact on health. This approach significantly benefits our daytime functionality, brain health, hormonal balance, and immune system.

3. Circadian Lighting and Seasonal Depression

The interplay between light exposure, mood, and mental well-being is significant, particularly highlighted by research during the pandemic era. Access to natural sunlight, a critical source of Vitamin D, has been emphasized for its health benefits. Vitamin D absorption through the skin is essential for preventing bone loss and reducing the risk of certain cancers and heart diseases.

Seasonal Affective Disorder (SAD), often termed seasonal depression, is recognized as a major depressive disorder with a seasonal pattern, predominantly occurring in winter. This condition is more prevalent in higher latitude regions where natural light is limited due to extended nights. Research points to two primary theories explaining SAD. The first theory suggests that reduced natural light alters sleep patterns and hormonal balances, contributing to depressive symptoms. The second theory posits that individuals with SAD have brain chemistry that’s particularly sensitive to light changes, exacerbating the disorder.

Studies underscore the critical role of natural light in mitigating SAD symptoms and enhancing overall mental health. Effective light exposure, particularly during morning hours, has been shown to synchronize the body’s internal clock, improve mood, and increase alertness. As such, integrating structured natural light exposure into daily routines is recommended for combating seasonal depression and promoting mental well-being.

This research-backed insight underscores the necessity of natural light for mental health, especially in combating conditions like SAD. It highlights the importance of outdoor activities and structured light exposure as vital components of mental health strategies, particularly in regions with limited daylight during certain seasons.

4. Implementing Circadian Lighting at Home and Work

Implementing circadian lighting in both home and workplace environments can significantly enhance daily well-being and productivity. Here are practical tips and examples to effectively integrate circadian lighting:

1. Evaluate Natural Light Sources: Start by assessing the natural light in your spaces. Maximize sunlight exposure through windows and consider room orientation to plan lighting accordingly.
2. Choose Adjustable Lighting: Invest in lighting solutions that allow control over both brightness and color temperature. LED lights with dimming capabilities and color temperature adjustments ranging from warm (2,700K) to cool (6,500K) are ideal.
3. Use Smart Lighting Systems: Smart bulbs and lighting systems can be programmed to mimic the natural progression of sunlight throughout the day. Set them to emit cooler, brighter light during the morning and warmer, dimmer light as the evening approaches.
4. Incorporate Task Lighting: For workspaces, use task lighting with adjustable brightness and color temperature to match the task at hand and the time of day, enhancing focus and reducing eye strain.
5. Opt for Circadian Lighting Products: Explore products specifically designed for circadian rhythm support, such as circadian ceiling panels, biodynamic light fixtures, and wearable light therapy devices.
6. Consider Timing and Placement: Position lights to complement natural circadian rhythms, with brighter lights in living and work areas during the day and softer lighting in relaxation and sleep areas in the evening.
7. Regular Adjustments: Regularly adjust your lighting setup based on the season and personal schedule to align with natural light variations and individual needs.

By strategically integrating circadian lighting, you can create environments that support natural sleep-wake cycles, improve mood, and enhance overall health and productivity.

5. Case Studies and Success Stories

In this section, we explore real-world applications and the impactful benefits of circadian lighting through two distinct case studies: the implementation of “Smart” Lighting in Swedish classrooms and innovative lighting solutions in the Stockholm Metro System. These examples highlight the tangible improvements in sleep patterns, mood, alertness, and productivity resulting from strategic lighting adjustments that align with the human circadian rhythm.

5.1. “Smart” Lighting In Swedish Classrooms

As we discussed, the circadian clock is the biological cycle that makes humans feel natural occurrences, such as sleep and hunger. During winter, the circadian clock changes, and therefore changes the body’s usual functions. The most popular theory about why the circadian clock is altered in the winter is the “phase shift hypothesis.” The colder, shorter days leave the body thinking it is a different time of day than it actually is, which leads to melatonin release at incorrect times. Melatonin is a hormone which causes sleep and therefore controls the sleep cycle. This means that during winter, people may get less sleep, causing lower mood levels.

BrainLit is a Swedish company that develops lights to mimic the circadian clock. BioCentric Lighting is their lighting solution which changes the intensity, wavelength, direction, timing, and duration of their LED lights to best align with human’s biological clocks. The system is a smart system, controlled by a light controller, it gets information from sensors to control the different lights. Higher alertness, better sleep, and increased productivity are some of the reviews that people have experienced. BioCentric Lighting are present in public areas such as schools and offices, places where people spend a majority of their day inside. 

5.2. Solutions in the Subway

Researchers at the KTH Royal Institute of Technology in Sweden looked into the effects that subway lighting has on the circadian rhythms of the body, since humans are not being exposed to as much natural light during the long winter night. The paper is titled, “Lighting Evaluation and Design for the Stockholm Metro System Based on Current Models for Nonvisual Responses”. About a million people ride the subway system in Sweden each week, which is a significant amount considering only about 10 million people live there.

As we have discussed in a previous article on blue light effects, high energy, shorter wave length light has a greater impact on melatonin suppression. This paper studied the “non-visual” effects of subway light, which quantifies sleepiness versus alertness. The Circadian Light (CL) and Circadian Stimulus (CS) models were utilized to turn these non-visual effects into measurable numbers. The CL model is a non-linear equation that looks at how much illuminance effects the body’s circadian rhythm, by looking at melatonin levels. The CS model includes the circadian light model, but directly calculates the amount of melatonin suppression. Melatonin level is how “sleepiness” is being measured. 

The average travel subway travel time in Sweden is about 20 minutes. This paper researched if this amount of time spent under light is enough to counteract the negative effects of limited daylight, which on the shortest day only lasts 6 hours. Many of the passengers aboard take the metro in the morning and evening, or the crucial parts on the circadian clock where humans wake up or sleep.

An image of the specific train car researched is shown below. 60 spots around the car were examined for its spectral power distribution and illuminance. A spectral power distribution contains all the physical properties of light, such as color. Values were also recorded for the Circadian Stimulus model for the 60 points. The spectral power distribution was graphed for all points, and it was found that all areas had nearly identical values, pointing to illuminance being the main factor for impacts on circadian rhythm. 

The Light in the Train Cars in the Swedish Metro. Photo courtesy of KTH Royal Institute of Technology.

After analyzing the illuminance data, it was found the standing areas had the highest circadian stimulus values, being the closest to the lights. The window seats have the lowest stimulus effects from the lights, being the furthest. The Lighting Research Center recommends indoor lighting has Circadian Stimulus values of at least 0.3 during the day time, and 0.1 at night, in order to have the least impact on the body’s inner workings. The window seats had an average values of 0.13, while standing areas had 0.29.

The light intensity and properties do not change throughout the day. These metro lights are not stimulating enough in the morning, while too harsh in the evening. Using LEDs that change illuminance and spectral power distributions throughout the day is the solution proposed by the Swedish researchers. These lights should emit shorter wavelengths during the morning, which increase stimulating effects, and decrease it during the night. 

6. Challenges and Considerations

Adopting circadian lighting presents a multifaceted challenge, intertwining considerations of technological sophistication, economic feasibility, and scientific understanding. Here’s an in-depth exploration of potential obstacles and considerations for a science and technology-oriented audience:

1. Economic and Technological Viability: The initial financial outlay for state-of-the-art circadian lighting systems can be significant, with costs varying widely based on the complexity and scale of the implementation. This economic barrier is compounded by the rapid pace of technological advancements in lighting, which can render systems obsolete and necessitate further investment. Ensuring a balance between cutting-edge technology and cost-effectiveness is paramount.
2. Complexity in Implementation and Operation: The intricacies involved in the installation, calibration, and operation of circadian lighting systems require a certain level of technical expertise. The systems often integrate with broader building management systems, necessitating a multidisciplinary approach to design and maintenance. Simplification and user-friendly interfaces, coupled with comprehensive training, can mitigate these challenges.
3. Scientific Literacy and Public Perception: Despite a growing body of research underscoring the benefits of aligning artificial lighting with natural circadian rhythms, there remains a significant gap in public awareness and understanding. Misconceptions, particularly around the use of blue light, persist due to its vilification in the context of screen time. Educational initiatives aimed at disseminating research findings and clarifying these misconceptions are crucial.
4. Regulatory Landscape and Standardization: The nascent field of circadian lighting is yet to see the establishment of universally accepted standards and regulations, akin to those that exist for traditional lighting in terms of safety and efficiency. The development of such standards, informed by the latest scientific research, will be critical in ensuring the efficacy and safety of circadian lighting solutions.
5. Interindividual Variability in Circadian Rhythms: Human circadian rhythms exhibit a significant degree of variability, influenced by genetic, environmental, and lifestyle factors. This heterogeneity poses a challenge to the design of universally effective circadian lighting solutions. Emerging research suggests that personalized lighting schemes, tailored to the individual’s circadian phenotype, may hold the key to maximizing the benefits of circadian lighting.

Addressing these challenges requires a concerted effort from scientists, technologists, policymakers, and educators. It involves not only advancing the technological and economic feasibility of circadian lighting solutions but also expanding the scientific understanding and public awareness of the profound impact of light on human health and well-being.

7. Future of Circadian Lighting

The future of circadian lighting is poised at an exciting confluence of technological innovation, scientific discovery, and increasing awareness of human health and well-being. Here’s an exploration of emerging trends and research directions in circadian lighting technology:

1. Personalized Circadian Lighting: Advances in wearable technology and biometrics are paving the way for personalized circadian lighting systems that adjust in real-time to an individual’s physiological needs. Research is focusing on integrating data from devices that monitor sleep patterns, activity levels, and even hormonal cycles to dynamically tailor lighting environments.
2. Integration with Smart Home and Building Systems: Circadian lighting is increasingly being integrated into broader smart building ecosystems, leveraging Internet of Things (IoT) connectivity. This allows for sophisticated control systems that can adapt not only to time of day but also to occupancy patterns, weather conditions, and even the specific activities being performed in a space.
3. Advancements in Light Source Technology: The development of new light-emitting materials and technologies promises more efficient and versatile light sources. Organic LEDs (OLEDs) and tunable LEDs, which offer a broader spectrum of light wavelengths and finer control over intensity and color temperature, are at the forefront of this trend.
4. Cross-disciplinary Research: The field of circadian lighting benefits from cross-pollination with neuroscience, chronobiology, and environmental psychology. Ongoing research is deepening our understanding of how light influences cognitive function, mood, and biological processes, leading to more effective and health-centric lighting designs.

The trajectory of circadian lighting technology is marked by a holistic approach that considers not just the visual aspects of light but its profound impact on human biology and well-being. As research continues to unfold, the integration of circadian lighting into our daily environments promises to enhance not only our physical and mental health but also our overall quality of life.

8. Conclusion

In conclusion, circadian lighting stands at the forefront of innovative solutions designed to harmonize our built environments with the natural rhythms of the human body. This technology not only holds promise in mitigating the effects of seasonal depression, particularly prevalent in arctic regions with limited daylight during winter months, but also in enhancing overall well-being through improved sleep patterns, mood regulation, and productivity.

Key Points Recap:

• Circadian lighting systems mimic the natural light cycle, supporting the synchronization of our internal biological clocks.
• These systems leverage advanced technologies and insights from fields like neuroscience and chronobiology to offer personalized and dynamic lighting environments.
• The integration of circadian lighting in settings such as workplaces, educational institutions, and public transportation systems like the Swedish Metro has demonstrated significant benefits, including heightened alertness and better sleep quality.
• Emerging trends in circadian lighting point towards a future where lighting is not only energy-efficient and smart but also attuned to individual health and wellness needs.

The adoption of circadian lighting, particularly in regions subjected to extended periods of darkness, offers a beacon of hope for alleviating the winter blues and enhancing daily life. As we continue to uncover the profound impact of light on human health, circadian lighting emerges as a pivotal element in designing spaces that nurture rather than negate our natural biological rhythms. Whether in the dimly lit corridors of a subway system or the confines of an office space, the strategic implementation of circadian lighting can transform our interaction with light, from a mere utility to a vital component of health and well-being.