One method to help with sleep and uplift mood involves adding bright light to your morning routine. Below, I explain how bright light helps with sleep and some simple ways to get bright light exposure during the day.
Our bodies are designed to wake up in response to brightly-lit environments and to sleep in dark ones. For example, bright light that enters our eyes through the retina transmits cues to our internal clock, a brain structure called the suprachiasmatic nuclei. Our internal clock regulates endogenous melatonin production, or melatonin that we naturally produce over the duration of the day. Melatonin is a hormone that facilitates sleep at high levels. It is suppressed with exposure to bright light1.
Importantly, light exposure during the day is linked with how quickly we fall asleep and how well we sleep during the night. In this article, I explain how light during the day helps with sleep at night and practical tips for lighting to help with sleep.
Bright light during the day helps with achieving high quality sleep at night
Sleep and light expert Dr. Mariana Figueiro often says, “brighter days, better nights.” Several studies led by Dr. Figueiro have shown that light exposure is related to sleep at night2.
A key research study on light exposure and sleep was a natural experiment in office workers. The researchers compared sleep quality in people who worked in offices with high exposure to natural light (e.g., windows) as compared to those who did not. They measured morning light exposure at eye level using a device called The Daysimeter.
Interestingly, people who had higher morning light exposure reported falling asleep more quickly at night and experiencing better sleep quality. Specifically, high morning light exposure was linked with falling asleep in under 18 minutes, but low morning light exposure was linked with taking nearly 45 minutes to fall asleep. The sleep quality differences between the two groups reflect global or general sleep quality, measured using the Pittsburg Sleep Quality Index. Better global sleep quality involves sleeping continuously throughout the night (i.e., without interruption), no use of sleep medications, and feeling alert throughout the day.
Bright light, better mood, and better sleep are intertwined
In addition to facilitating high quality sleep at night, the same study in office workers showed that morning bright light exposure during the day is related to lower depressive symptoms. Given research on treating seasonal affective disorder (i.e., SAD) with bright light exposure, this is expected. Morning bright light exposure is linked with remission of clinical depression.
Sleep quality and mental health are intertwined. For example, depressive symptomology and poor sleep have a reciprocal relationship. In some cases, poor sleep can precede depression, and in others, depression precedes poor sleep. The research suggests that intervening on environmental light may improve other outcomes. One experimental study has shown that patients with Alzheimer’s disease in an intervention condition exposed to morning bright light reported reduced depression symptoms and better sleep quality as compared to a baseline condition before they were exposed to bright light.
Taken together, poor sleep and depressive symptoms are interlinked. But, bright light exposure, especially in the morning hours, may help improve sleep quality and uplift mood.
Limit bright light exposure during the nighttime
Bright light exposure is helpful for sleep during the day, but it is disruptive to sleep at night. One recent academic review recommends that the sleep environment at night should be “as dark as possible”3. Several research studies have shown that light exposure close to bedtime is associated with poor sleep. One experimental study in young adults demonstrated that people who did not use their phones for 30 minutes before bedtime reported falling asleep quicker and better quality sleep than people who did use their phones before bed. This study provides evidence for the common sleep recommendation for removing backlit electronic devices from the sleeping environment.
Interestingly, a study found that using “night shift” mode before bed does not provide any meaningful benefit over using the default light settings. There are several mechanisms that could explain sleep disruption from backlit electronic devices in the sleeping environment. One is that light from the phone may suppress melatonin and delay sleep onset. Another is that mobile devices can be used to engage with apps that are linked with greater pre-sleep arousal (e.g., Tik-Tok). When we feel high levels of cognitive engagement, excitement, or worry, it takes longer to calm down and fall asleep. Both the light and the context in which we experience it matter for sleep.
Tips to take away
Above, we’ve gone through several research findings about light during the day and night that may affect the way that we sleep. Based on these studies, I summarize some tips on how to control the light in your environment to help with achieving optimal sleep health.
- Have a “bright” day. Light exposure during the daytime is helpful for sleeping at night. Consider spending time outdoors with natural sunlight, or sitting near a window during the day. Also, use bright ambient light indoors when available (e.g., turn on a room light instead of only lighting your workspace during the day). Importantly, aim for direct exposure to the light during the daytime, especially in the morning (illustration below).
- Sleep in a dark room. We all know that it’s easier to sleep in a dark room instead of a bright one. If you tend to be a late riser, you may benefit from blocking outdoor light before you wake up. Try using blackout curtains to block artificial light sources during the night, or use something to cover your eyes (e.g., eye mask, scarf) if you need to.
- Limit time with (light-emitting) electronic devices near bedtime. Limiting time with electronic devices before bed is helpful for sleep. At a minimum, I suggest putting away electronic devices at least 30 minutes before bedtime.
- Find calmness before bed. Some researchers have suggested that device use before bed may be linked with pre-sleep arousal, or high levels of cognitive agitation. Prioritize activities that help you feel peaceful before bedtime. Some calming activities could include gentle yoga stretches, meditation, or taking a warm shower or bath.
The two most important points made in this article are 1) bright light during the day at eye level and 2) limiting bright light during the night both help us to have nights of high quality sleep. I wish you bright days, dark nights, and restful sleep.
The ideas presented here are my own and do not substitute individualized medical advice. If you are having consistent trouble with your sleep, I recommend seeking help from a trusted medical profession.
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- For a detailed discussion on the neuroscience of light and sleep/wake cycles, see this academic review article. ↩
- An academic review on the effects of light exposure on sleep, see Dr. Figuerio’s article here. ↩
- To be sure, the authors also note that it is important to have a light source for navigating during the night if you have to get up to go to the bathroom, for example. It may be helpful to have a dim flashlight near the bed or a red night light in other rooms for easy navigation that is not disruptive to sleep. ↩