Want better mental health? Make sure you're sleeping in a pitch black vault

Your eyes drift open, you inhale sharply and wipe the drool from your chin while you slowly register that your TV is asking if you're still watching whatever show seduced you into bingeing yourself to sleep on your sofa. Again. Your brain chirps up with "No TV, I am not — in fact, I should be in bed". And your brain is right, you should be. Aside from doing your spinal column precious few favours on that couch, recent science suggests you may also be doing your mental health a serious disservice when you fall asleep bathed in even the smallest amount of light.

Strong findings from a study published in the American Journal of Epidemiology have correlated even very low levels of nighttime light with depressive symptoms in the elderly. It's worth appreciating that the low light here really is quite minimal: around 5 lux – which, give or take a lux, is comparable to the brightness of a candle flame at 2 feet. Researchers note they opted for older subjects, most of whom were retired and over 60 years of age in order to "minimize the effect of office environments and current work" on study data. That data was yielded over two years from 863 participants, at an average age of 71.5, who all kept a regular sleep journal and showed a willingness to having various lights installed on their bedroom ceilings for science.  

Compellingly, while none of the subjects reported depression of any kind at the outset, upon follow-up 2 years later, 73 participants had developed measurable depressive symptoms. Most crucially, participants who were exposed to more than 5 lux of light at night "exhibited a significantly higher depression risk" than the "dark" group (who were subject to less than 5 lux). Relevant aside: Light At Night is now enough of a health concern to warrant its own scientific shorthand: LAN. Kenji Obayashi, study co-author and professor in the department of community health and epidemiology at Nara Medical University School of Medicine in Japan says his research makes a strong case for bedding down in a pitch black room LAN-free. It may be time to enforce harsher household rules aimed at banishing electronics in the bedroom — and/or incorporating some very opaque blinds into your window dressing design scheme.

Blue light is everywhere in our homes (mostly glowing out of screen devices and from energy-efficient lighting) and it confounds the evolutionary mechanism that makes our bodies produce sleep-inducing melatonin come nightfall. Or as the study puts it "circadian timing system in humans has adapted to the natural environment based on daytime light and nighttime dark." This study makes the observation that rates of depression have risen in recent decades and offers that "exposure to light at night (LAN) is the strongest disruptor of circadian physiology and behavior."

Still, if you're resting easy, boldly bathed in blue light because you aren't part of the septuagenarian set, consider that younger people may actually be even more sensitive to disruptive nighttime light. The fresher your eyeballs, the higher your risk of shoddy sleep cycles should a light source be visible from your bed. Obayashi explains that "the capacity for light reception of a 70-year-old is one-fifth of that of a teenager." Unsurprisingly, screen devices are not helping teens get more Zzzzzs.   

This isn't the first study to examine the effects of nighttime light and depressive symptoms. One study demonstrated that nightly light exposure significantly increased depression-like behavior in hamsters. Again here, confidence that there are no hamsters in your bloodline provides little justification to light it up at night. The study is careful to point out that human "prevalence of major depression has increased in recent decades" and that "exposure to artificial light at night (LAN) has surged in prevalence during the past 50 years, coinciding with rising rates of depression." Managing nighttime brightness may be particularly relevant for women. The same study also explains that they're "twice as likely as men to develop the disorder". Happily, the study also showed that all hamsters enjoyed an up-spike in mood when LAN was traded for darker sleeping quarters.   

Should a more human example serve, still another study showed an observable link between  working the night-shift and greater risks for depression, anxiety and fatigue — all due to persistent disruptions of circadian rhythms when exposure to LAN was high. Obayashi's study echoes those findings. He told media that "maintaining darkness in the bedroom at night may be a novel and viable option to prevent depression." As an aside, one wonders if basement apartments devoid of natural light will enjoy a jump in popularity?       

The scientific case for pitch black cocooning has been made. If managing your moods is high on your priority list, the solution could be to get pretty precious with the darkness of your sleeping quarters. Eye masks, full body sleeping bags, no electronics anywhere near the bedroom, blackout curtains. Do what you gotta do, because science seems to be offering us an elegant equation: dark bedroom = bright mood.

Marc Beaulieu is a Montreal writer, producer, performer, professional host and mental health advocate whose one true love is weird news.