Natural light may be key to improving mood and reducing insomnia

A new study led by Monash University has revealed that getting enough natural sunlight each day can impact a person’s mood and sleep quality.

Monash University Turner Institute for Brain and Mental Health PhD student Angus Burns and Associate Professor Sean Cain led an international research team that has had their work published in the upcoming December issue of the Journal of Affective Disorders.

The cross-sectional and longitudinal study of more than 400,000 participants in the UK Biobank program found that a lack of daytime light exposure was a risk factor for depressive symptoms, poor mood, and insomnia.

Mr Burns said that most messaging around light and health is focused on avoiding light at night, as it disrupts our body clocks, but this study highlights the importance of getting enough daylight to ensure our bodies function optimally.

“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,” Mr Burns said.

“These results may be explained by the impacts of light on the circadian system and the direct effects of light on mood centres in the brain.”

Associate Professor Cain said making minor adjustments to a person’s daily routine could help 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,” he 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.”

Read the full paper in the Journal of Affective Disorders tilted: Time spent in outdoor light is associated with mood, sleep, and circadian rhythm – related outcomes.  A cross-sectional and longitudinal study in over 400,000 UK biobank participants.
DOI: 10.1016/j.jad.2021.08.056