Too much light at night can prevent you from falling asleep or staying asleep, but not enough light during the day can also be a problem. Researchers at Monash University in Australia found that not getting enough natural sunlight each day has a direct impact on a person’s mood and sleep quality.
Monash researchers looked at data from more than 400,000 participants in the UK Biobank program and determined a lack of daytime light exposure was a risk factor for depressive symptoms, poor mood and insomnia. They found the more time a person spends in outdoor light, the lower the odds they will experience a major depressive disorder during their lifetime.
The results of the cross-sectional and longitudinal study were published in the Journal of Affective Disorders.
Lead researcher Angus Burns said most of the messaging regarding light and health is centered on avoiding light at night because of its ability to affect our internal body clock and disrupt sleep. What he and the team discovered is that it’s just as or more important to get enough daylight each day to ensure our bodies function properly.
"In this study, we observed that the greater time spent in outdoor light during the day was associated with fewer depressive symptoms, lower odds of using antidepressant medication, better sleep and fewer symptoms of insomnia," Burns said. "These results may be explained by the impacts of light on the circadian system and the direct effects of light on mood centers in the brain."
Fellow researcher Sean Cain said even small adjustments to a person’s daily routine that includes more natural daylight could be enough to improve their mood, sleep and energy levels.
"People now spend most waking hours in intermediate, artificial lighting conditions, due to reduced sunlight exposure and relatively bright night-time light exposure," Cain said. "In this study, we observed that greater time spent in outdoor light was associated with better mood outcomes, better quality sleep, and ease of wakening.
"Insufficient exposure to daytime light could be a key factor contributing to poor mood and sleep outcomes in depressive disorders. My general advice for everyone is simple: When the sun is out, get as much light as you can, but after it sets, keep it dark. Your body will thank you."