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Lighting affects mood through pathways to the brain's clock center.

Bluish light increases alertness, while warm yellow-reddish light calms and relaxes.

Bright light improves mood and decreases depression, and dimmer light decreases energy and alertness.

It is estimated that Americans spend over 90 percent of their days indoors. Therefore, when thinking about easily modifiable interventions to improve mood, we should consider the features of indoor environments. The most important of these is light.

Research shows that lighting brightness, "color temperature," timing, rhythm, and locations of indoor lighting can all improve mood.

The first four—brightness, "color temperature," timing, rhythm—all affect mood through the brain’s non-visual (non-image forming) pathways, starting when light hits special receptors at the back of the eye, which send signals directly to the brain’s clock center. The fifth (location) affects mood through the brain’s visual pathways.

Brightness and Color Temperature

Color temperatures of light, measured in Kelvin (K), are not actually blue or red, but are at the blue and red ends of the color spectrum. Think of the bright blue sky in the early morning, shifting to a reddish sky in the evening at sunset. At the lowest end, 2200K lighting is equivalent to candlelight, while the high end, 4000K, is equivalent to bright full-spectrum morning sunlight. You can find examples on the web of rooms lit with different temperatures of light to see the difference.

Many studies have shown that bright white (bluish) light, either delivered through full-spectrum light boxes or sun exposure, can help prevent and reduce depressive symptoms in people with seasonal affect disorder (SAD). Recent studies also indicate that it reduces depressive symptoms and enhances positive emotions and alertness in people without depression.

A recent study in older adults comparing all-day exposure over 18 days to different intensities and color temperatures of light found that lighting that shifted from bright light in the early morning to dimmer light in the evening, with color temperature staying in the mid-range (warm white or yellowish, like incandescent lighting), significantly reduced depressive symptoms both in those with and without elevated depression scores. However, when both the intensity and color temperature of the light shifted from bright to dim and from bluish to reddish through the day, the impact on reducing depression scores was even greater in both depressed and non-depressed individuals. This pattern of light exposure also improved positive mood scores. Another study in elderly patients with dementia found that a similar 25-week lighting intervention improved sleep and reduced depression and agitation, and that these effects were cumulative over time.

This indicates that the rhythm and timing of exposure to lighting is important. Studies show that 30 minutes of exposure to bright bluish light in the morning between 8 a.m. and 12 noon improves mood and reduces depressive symptoms by improving sleep quality. People exposed to bright bluish morning light fall asleep faster, have better quality sleep, and wake up in a better mood and feeling less fatigued the next day.

But exposure to bright bluish light at any time of day reduces depressive symptoms and enhances alertness even without affecting sleep. Thus, 15-30 minutes’ exposure to bright bluish light can increase alertness as much as a cup of coffee. This is a good thing if you take your dose of light during the day—it is energizing. But if timed poorly, it can impair mood. Exposure to bluish light in the evening, like from a computer or cell phone screen, can result in poor sleep quality and worsened mood the next morning. Light that is too bright with glare is also stressful and should be avoided at all times of day.

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The best kind of indoor light exposure to enhance mood, improve sleep, and reduce depressive symptoms is lighting that varies throughout the day, as does the sun. Such circadian lighting would typically start in the morning with bright bluish light and gradually shift to dimmer, redder light in the evening before bedtime. While this can be achieved through light pouring into indoor spaces through glass walls or lots of windows, smart LED lighting can also provide such nuanced indoor lighting rhythms. Other technologies, like wearing glasses that block blue light in the evening, and using red LED lights for reading at night, can also help set your circadian clock for healthy sleep and a positive mood.

Placement of lighting in indoor spaces also matters because visual inputs of features of the space and items in it can affect mood through the brain's memory pathways. Design professionals have developed ways of enhancing relaxation and creating intimate spaces for connection by softening indoor lighting, indirect lighting, and layering lighting in rooms. Similarly, lighting can be used to focus attention on desired objects and spaces.

So, if you’re feeling down when you wake up in the morning, consider taking time out in the morning to be bathed in bright bluish, full-spectrum light for 30 minutes—either with smart indoor lighting or outdoors in the sun. If you’re feeling down and fatigued in the afternoon, consider a dose of bright bluish light instead of that cup of coffee to improve your mood and alertness. But don’t take that lighting dose too close to bedtime, or your sleep will be impaired.

Aryani, S. M., Kusumawanto, A., Suryabrata, J. A., & Wijaya, D. D. (2024). The correlation of lighting and mood in the workplace: digital image-based research. Journal of Graphic Engineering and Design, 15(1), 23-31.

Figueiro, M. G. (2020). Future directions for lighting environments. In Circadian rhythm sleep-wake disorders: An evidence-based guide for clinicians and investigators (pp. 221-240). Cham: Springer International Publishing.

Figueiro, M. G., Sahin, L., Kalsher, M., Plitnick, B., & Rea, M. S. (2020). Long-term, all-day exposure to circadian-effective light improves sleep, mood, and behavior in persons with dementia. Journal of Alzheimer's disease reports, 4(1), 297-312.

Figueiro, M. G., Steverson, B., Heerwagen, J., Kampschroer, K., Hunter, C. M., Gonzales, K., ... & Rea, M. S. (2017). The impact of daytime light exposures on sleep and mood in office workers. Sleep health, 3(3), 204-215.

Kong, Z., Liu, Q., Li, X., Hou, K., & Xing, Q. (2022). Indoor lighting effects on subjective impressions and mood states: A critical review. Building and Environment, 224, 109591.

Nussbaumer‐Streit, B., Forneris, C. A., Morgan, L. C., Van Noord, M. G., Gaynes, B. N., Greenblatt, A., ... & Gartlehner, G. (2019). Light therapy for preventing seasonal affective disorder. Cochrane Database of Systematic Reviews, (3).

Philips HealWell White Paper Backgrounds on Light and Health and Descriptions of the HealWell System. https://www.assets.signify.com/is/content/PhilipsConsumer/PDFDownloads/…

Shishegar, N., & Boubekri, M. (2022). Lighting up living spaces to improve mood and cognitive performance in older adults. Journal of Environmental Psychology, 82, 101845.

Sternberg, E.M. (2023) Well at Work: Creating Wellbeing in Any Workspace (Little, Brown Spark Sept. 2023)

Sternberg, E. M. (2009). Healing spaces: The science of place and well-being. Harvard University Press.

Zhou, B., Zhou, Y., Ren, Q., Peng, L., Guan, Y., & He, H. (2025). Research on the Impact of Lighting Illuminance and Color on Creative Performance and Mood. Buildings, 15(10), 1738.

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