Getting enough sleep belies mental and physical health—one bad night of shut-eye can attest to that fact. So it comes as no surprise that anything that instrumentally disrupts your sleep schedule on a regular basis can lead to mental health issues over time.
It's common knowledge that watching Netflix or checking your phone before bed (or when you wake up in the middle of the night) is bad for your eyes, sleep schedule, and overall health. But as My Body+Soul reports, a new study published in the Nara Medical University journal has found that even a small hint of light—whether it's natural light peeking through your blinds, a small stream of light from the hallway, or the blue light from your smartphone—can disrupt your body clock and increase the risk of depression over time.
Between 2010 and 2014, lead study author Kenji Obayashi, MD, PhD, and team oversaw 863 elderly Japanese participants split into two groups with differing light exposure levels during sleep. They asked participants to keep a diary and complete regular surveys throughout the study to track the potential development of depressive symptoms. While none of the participants had depressive symptoms at the beginning of the study, those who were exposed to more than five lumens of light at night (the measurement for the total amount of light emitted by a light source over a period of time) had a higher risk of developing depression, as compared to those who slept in complete darkness.
For reference, a standard 75-watt light bulb emits 1100 lumens of light.
As always, these findings should be taken with a grain of salt, especially considering the limited sample size, lack of geographic diversity, and the limited age range involved in the study as well as the countless other factors that can also contribute to depression. Nevertheless, there's a baseline connection between quality of sleep and both mental and physical health, and we could all stand to be mindful about the number of hours we're clocking as well as whether or not our environments are conducive to good, quality sleep.
Head over to the American Journal of Epidemiology for more.