The Impact of Daily Light Exposure on Mental Wellbeing

Exposure to light after dark could heighten the likelihood of mental health disorders, recent findings indicate.

In an objective study involving over 85,000 individuals, published in “Nature Mental Health,” researchers have linked nighttime light consumption with an increased risk of conditions like anxiety, bipolar disorder, and PTSD, as well as a heightened likelihood of self-harm.

Conversely, the study also highlights the benefits of absorbing more light during the day, suggesting it can serve as a natural therapeutic option to diminish the risk of psychosis and enhance mental health overall.

Sean Cain, PhD, an associate professor at Monash University and contributor to the study, emphasizes the significance of adhering to the innate lighting pattern of bright days and dark nights — a regime that aligns with the human body’s evolutionary conditioning.

Understanding how light timings affect mental health and how to harness light exposure to benefit circadian rhythms are pivotal discussions stemming from this research.

Exploring Day and Night Light Exposure’s Mental Health Impact

A comprehensive study involving 87,000 participants set out to examine the connection between light exposure, the body’s internal clock, and mental health outcomes. Over a week, participants’ exposure to light and sleep patterns were meticulously recorded to establish the relationship between their circadian rhythm and mental health.

The research process included tracking the participants’ light exposure both day and night and assessing their mental health through a detailed questionnaire following the exposure period.

The findings revealed a notable pattern: high levels of light at night increased depression risk by 30%, while ample daylight exposure was associated with a 20% decrease in depression risk. These trends were consistent across other mental health issues, including PTSD, anxiety, self-harm, bipolar disorder, and psychosis.

Cain, a contributor to the study, noted the paradox that while light exposure can provide immediate relief, it may be detrimental in the long run, disrupting natural rhythms and potentially exacerbating mental health issues.

Understanding Circadian Rhythms and Light Exposure

Daylight plays a crucial role in regulating the body’s circadian rhythm, which is the internal clock that orchestrates the body’s functions. Exposure to daylight helps align our physiology, while nocturnal light disrupts the rhythm, weakening the body’s natural timing mechanisms.

Our body’s various tissues operate on daily cycles governed by a master clock in the brain, which is tuned to expect light during the day and darkness at night. Deviations from this expected pattern, such as dim daytime environments or bright nighttime settings, can disturb this cycle, leading to a host of health issues including sleep disturbances, cardiovascular problems, obesity, and more.

However, Cain points out that not all light affects the body equally. Natural light, which is typically much brighter than we perceive due to our visual system’s adjustments, plays a beneficial role in regulating our rhythm. Artificial light, if it includes more blue wavelengths, can be optimized to emulate the positive effects of natural light on our circadian clocks. This can be particularly beneficial for those who spend significant amounts of time indoors.

Cain also addresses a common misunderstanding regarding blue light. While detrimental at night, blue light can be beneficial during the day, playing a positive role in maintaining our circadian rhythm.

Optimizing Light for Circadian Health

To foster a well-regulated circadian rhythm, it’s beneficial to absorb as much bright daylight as you can, which bolsters both physiological rhythms and mood. However, completely avoiding light at night might not be practical.

Cain advises utilizing intelligent lighting systems that can automatically transition to a softer, warmer glow, reminiscent of candlelight, as night falls. This gentler light is less disruptive to our circadian clocks. By dimming lights a few hours before bedtime, one can encourage the body’s natural rhythm to synchronize with sleep time more effortlessly.

Another supportive strategy for circadian health is red light therapy. A 2019 study demonstrated that a mix of red and white light used in the afternoon can enhance circadian rhythms and alertness. This approach can be particularly advantageous for those dealing with seasonal affective disorder (SAD), which often sets in with the reduced daylight of winter months and can alter serotonin and melatonin production, thus affecting circadian rhythms.

Rivera Cruz, a licensed therapist, suggests that in addition to regular exercise, sleep hygiene, and a nutritious diet, therapies like red light treatment or SAD-specific lamps can offer significant benefits. For maximum impact, she recommends engaging in light therapy for 20 to 30 minutes upon waking and potentially adding sessions later in the day. Evening light therapy should cease at least an hour before bedtime to prevent interference with sleep.

Using light therapy throughout the winter, especially before and after daytime light exposure, can enhance its effects. Such therapies not only aid mental health but also support wound healing and pain management, according to Cruz.


  1. Day and night light exposure are associated with psychiatric disorders: an objective light study in >85,000 people
  2. The Neurobiology of Circadian Rhythms
  3. Effects of light on human circadian rhythms, sleep and mood
  4. The Neurobiology of Circadian Rhythms
  5. Sleep Dysfunction and Gastrointestinal Diseases
  6. Light, entrainment and alertness: A case study in offices

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