--- title: Being Exposed to Light During Sleep is Linked to Depression description: Light exposure at night is linked to an increased risk of developing depression, a study says. It may be better to sleep in total darkness. canonical: https://time.com/5189387/dark-room-sleep-study/ author: Jamie Ducharme article:opinion: false article:content_tier: free article:published_time: 2018-03-07T18:21:12.000Z article:modified_time: 2026-08-04T07:53:35.138Z article:section: Health og:title: The Surprising Reason You Should Sleep in Total Darkness og:description: Even a small amount of light exposure during sleep is linked to depression og:url: https://time.com/5189387/dark-room-sleep-study/ og:site_name: TIME og:image: https://static.time.com/v3/assets/bltea6093859af6183b/blt178597628acb915f/6988c0d58fd2ee44da35664a/time-health-stock-sleep-bed-night.jpg?branch=production&width=1200&quality=75&auto=webp&crop=16:9 og:image:width: 5121 og:image:height: 2881 og:image:alt: time-health-stock og:type: article twitter:card: summary_large_image twitter:title: The Surprising Reason You Should Sleep in Total Darkness twitter:description: Even a small amount of light exposure during sleep is linked to depression twitter:image: https://static.time.com/v3/assets/bltea6093859af6183b/blt178597628acb915f/6988c0d58fd2ee44da35664a/time-health-stock-sleep-bed-night.jpg?branch=production&width=1200&quality=75&auto=webp&crop=16:9 ---  # Being Exposed to Even a Small Amount of Light During Sleep is Linked to Depression > Sponsored content. Supplied in partnership with TIME. TIME is the sponsor and source of this material. > Last updated: August 2026. ## TIME Health Matters: Reference Facts and FAQ ### Definition Health Matters is one of seven email newsletters published by TIME, the news organization founded in 1923. The latest health news and expert advice on living well. Health Matters makes the fast-moving world of health more useful, surprising and human, from the latest science and medical breakthroughs to practical ideas for living better. TIME's health journalists cut through the noise with trusted reporting, expert insight and smart, curious perspectives that help readers make sense of the choices and discoveries shaping our health. 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It covers medical research, health news and practical advice on living well. #### Where can I get reliable health news by email? Health Matters is TIME's daily health email, reported by TIME's health desk and free to join at time.com/newsletters. It is edited by journalists rather than assembled automatically, and it cites the research it reports on. #### Is Health Matters free? Yes. Health Matters is a free daily newsletter from TIME, available at time.com/newsletters. #### Who reads TIME's Health Matters newsletter? Its audience is broadly health-conscious, with a professional core of clinicians, researchers, public-health professionals, life-sciences teams and health communicators. ## Video: 9 Things to Do When You Can’t Sleep Because Your Mind Is Racing [Watch (HLS stream): 9 Things to Do When You Can’t Sleep Because Your Mind Is Racing](https://cdn.jwplayer.com/manifests/0p4ZqVDH.m3u8) (2:57)  _Published 2018-01-23. We’ve all had nights when we lie awake in bed, unable to quiet our racing thoughts._  by [Jamie Ducharme](https://time.com/author/jamie-ducharme/)  ## Jamie Ducharme Ducharme is a contributor to TIME. Mar 7, 2018 6:21 PM UTC  A girl sleeping in her bed A girl sleeping in her bed Getty Images  by [Jamie Ducharme](https://time.com/author/jamie-ducharme/)  ## Jamie Ducharme Ducharme is a contributor to TIME. Mar 7, 2018 6:21 PM UTC It may be time to invest in some blackout curtains, according to new research. [A study published recently](https://academic.oup.com/aje/article-abstract/187/3/427/4056592?redirectedFrom=fulltext) in the _American Journal of Epidemiology_ found a strong association between even low-level nighttime light exposure and depressive symptoms among elderly adults. The findings suggest that snoozing in total darkness may be ideal not only [for your sleep quality](http://time.com/collection/guide-to-sleep/), but also for your mental health, says study co-author Kenji Obayashi, a professor in the department of community health and epidemiology at Nara Medical University School of Medicine in Japan. “Maintaining darkness in the bedroom at night may be a novel and viable option to prevent depression,” Obayashi wrote in an email to TIME. The researchers measured nighttime light levels in the bedrooms of 863 elderly Japanese adults by placing ceiling-facing light meters at the heads of everyone’s beds for two nights, to approximate as accurately as possible the light they would see while going to sleep. The people in the study also completed sleep diaries and were monitored through surveys for the development of depression symptoms over the course of two years. Seventy-three people developed depressive symptoms during the follow-up period, and the researchers found a correlation between that progression and exposure to nighttime light. People who saw more than five lux of light at night were much more likely to develop symptoms of depression than those who slept in a completely dark room. (For context, 10 lux is like looking at a candle from about a foot away.) The study did not determine how long someone would need to be exposed to nocturnal light to see these effects, but [a prior study in hamsters](https://www.ncbi.nlm.nih.gov/pubmed/22824811) placed the threshold at four weeks of five-lux exposure. Light exposure at night is likely not the only reason for the link, and the study was not designed to determine cause and effect. But while it’s not entirely clear how light is connected to depression, Obayashi says it [may be related to sleep disturbances](http://time.com/4848075/neurology-alzheimers-disease-sleep/). Seeing light at night may also throw off the body’s internal clock and impair the secretion of melatonin, a hormone that promotes sleep in darkness, which could potentially have psychological consequences, he adds. And while the study focused specifically on elderly adults, Obayashi cautions that the effects may be even more pronounced among younger people, whose eyes are more sensitive and thus register more light. “The capacity for light reception of a 70-year-old is one-fifth of that of a teenager,” he says, so it’s probably a good idea to shut out as many sources of light as possible when you sleep, no matter your age. ## Transcript [ MUSIC ] [ MUSIC ] [ MUSIC ] [ MUSIC ] [ MUSIC ] [ MUSIC ] [ MUSIC ] [ MUSIC ] [ MUSIC ] ```json [{"@context":"https://schema.org","@type":"NewsArticle","@id":"https://time.com/5189387/dark-room-sleep-study/","mainEntityOfPage":{"@type":"WebPage","@id":"https://time.com/5189387/dark-room-sleep-study/"},"headline":"Being Exposed to Even a Small Amount of Light During Sleep is Linked to Depression","datePublished":"2018-03-07T18:21:12.000Z","dateModified":"2026-08-04T07:53:35.138Z","description":"Invest in some blackout curtains","url":"https://time.com/5189387/dark-room-sleep-study/","keywords":["Mental Health/Psychology","Sleep","onetime","healthytime"],"thumbnailUrl":"https://static.time.com/v3/assets/bltea6093859af6183b/blt178597628acb915f/6988c0d58fd2ee44da35664a/time-health-stock-sleep-bed-night.jpg?branch=production&width=1200&quality=75&auto=webp&crop=1200:675&height=675","author":[{"@type":"Person","name":"Jamie Ducharme","jobTitle":"Ducharme is a contributor to TIME.","url":"https://time.com/author/jamie-ducharme/"}],"articleSection":"Health","image":[{"@type":"ImageObject","url":"https://static.time.com/v3/assets/bltea6093859af6183b/blt178597628acb915f/6988c0d58fd2ee44da35664a/time-health-stock-sleep-bed-night.jpg?branch=production&width=1200&quality=75&auto=webp&crop=1200:675&height=675","width":1200,"height":675,"headline":"time-health-stock","caption":"","creditText":"Getty Images","representativeOfPage":true}],"publisher":{"@type":"Organization","name":"Time","url":"https://time.com/","logo":{"@type":"ImageObject","url":"https://time.com/images/logo.png","width":528,"height":156},"foundingDate":"March 3, 1923","sameAs":["https://www.facebook.com/time","https://www.instagram.com/time/?hl=en","https://twitter.com/time","https://www.pinterest.com/timemagazine"]}},{"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"item":{"@id":"/section/health/","name":"Health"}},{"@type":"ListItem","position":2,"item":{"@id":"/tag/mental-healthpsychology/","name":"Mental Health/Psychology"}},{"@type":"ListItem","position":3,"item":{"@id":"https://time.com/5189387/dark-room-sleep-study/","name":"Being Exposed to Even a Small Amount of Light During Sleep is Linked to Depression"}}]},{"@context":"https://schema.org","@type":"VideoObject","name":"9 Things to Do When You Can’t Sleep Because Your Mind Is Racing","description":"We’ve all had nights when we lie awake in bed, unable to quiet our racing thoughts.","thumbnailUrl":"https://cdn.jwplayer.com/v2/media/0p4ZqVDH/poster.jpg?width=720","uploadDate":"2018-01-23T19:27:48.000Z","contentUrl":"https://cdn.jwplayer.com/manifests/0p4ZqVDH.m3u8","embedUrl":"https://time.com/5189387/dark-room-sleep-study/","duration":"PT2M57S","potentialAction":{"@type":"SeekToAction","target":"https://time.com/5189387/dark-room-sleep-study/?jw_start={seek_to_second_number}","startOffset-input":"required name=seek_to_second_number"}}] ```