Sleeping with even a little bit of light in your bedroom at night can heighten depression, says a new study from the American Journal of Epidemiology. 

Even when other factors were taken into consideration — like whether the patients smoked, ate poorly, etc — this increase in light in the bedroom accounted for a big jump in depression. 900 elderly Japanese patients were studied over the course of 2 years and it was found that those with over 5 lux had a higher chance of developing depression by 60-65%. Out of the 900 people in the study, just 150 of those slept in rooms with more than 5 lux. 

A 'lux' is roughly the amount of light emitted from a candle 1 meter away. To put things in perspective, ABC News reports that a bedroom at night with the lights on is roughly 50 lux, while being outside in bright sunlight can reach anywhere from 10,000 to 25,000 lux. 

The study appears to show a correlation between circadian rhythms and light exposure and depression. With more and more people using their phones, tablets, and computers in the bedroom well into the night hours, this appears to lead to a higher risk of developing depression. Lack of sleep can a wide array of other health problems, including depression, weight gain, and even cancer.

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