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Sleeping With the Lights On? Sleep MD Explains Why It's Bad

Sleeping with the lights on may be a temporary help for anxiety, but light at night can damage your ability to sleep and cause health issues. Darkness is best.
Published
2021-11-11
Updated
2024-02-10
13 MINS
Written by
Jeff Kahn, M.S., Rise Science Co-Founder
Reviewed by
Chester Wu, MD, Rise Science Medical Reviewer
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We bring sleep research out of the lab and into your life. Every post begins with peer-reviewed studies — not third-party sources — to make sure we only share advice that can be defended to a room full of sleep scientists.
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Updated Regularly
We regularly update our articles to explain the latest research and shifts in scientific consensus in a simple and actionable way.
Woman unable to sleep when sleeping with the lights on

Sleeping With the Lights On? Try a Dark Bedroom Instead

  • Sleeping with the lights on can suppress the sleep hormone melatonin and disrupt your body clock.  
  • Light can make it harder to fall and stay asleep, disrupt your sleep stages, and lead to health issues like weight gain, type 2 diabetes, and depression.
  • The RISE app can tell you when you should be getting and avoiding light, and help you improve your sleep habits to make it easier to fall asleep — with (and eventually without) the lights on.

It might feel like sleeping with the lights on helps you drift off. But light can disrupt your body clock and lead to a long list of sleep and health problems.

But if you have anxiety — or no control over your environment — sleeping in darkness might not be an option either. 

Below, we’ll cover the effects of sleeping with the lights on, how to reduce how impactful sleeping with the lights on is, and how the RISE app can help you get better sleep with and without the lights.

Advice From a Sleep Doctor

Advice From a Sleep Doctor

“I recommend sleeping in a pitch black room. Sleeping with the lights on can lead to more nighttime awakenings and health issues like obesity, type 2 diabetes, and even depression. And your body can detect light, even when you’re sleeping,” says Dr. Chester Wu, Rise Science sleep advisor and medical reviewer, who’s double board certified in psychiatry and sleep medicine.

“If you feel like you can’t drift off without some light, make your bedroom as dim as possible. You could swap overhead lighting for a dim red light night light, for example.”

Is Sleeping With the Lights on Bad? 

Sleeping with the lights on is bad because light can disrupt your sleep and circadian rhythm (your internal clock). This can lead to sleep deprivation and circadian misalignment, both of which can lead to low energy, impaired mental performance, and mental and physical health problems like weight gain, depression, and type 2 diabetes — just to name a few.

Expert recommendations published in 2022 in PLOS Biology state “the sleep environment should be as dark as possible.” The maximum recommended amount of nighttime light is 1 lux. That’s pretty dark! For reference, twilight is 11 lux.  

We’ve covered more on the best color light for sleep, and other times of day, here.

Light intensity of different times and places
The light intensity of different times and places. Daylight is not direct sun.

What Are the Effects of Sleeping With the Lights On? 

The effects of sleeping with the lights on include trouble sleeping, circadian misalignment, disrupted sleep stages, and health issues like weight gain, obesity, changes in heart health, type 2 diabetes, mental health conditions, and Alzheimer’s Disease.

Here’s what we know about the potential side effects of sleeping with the lights on.

Trouble Falling and Staying Asleep 

Light exposure suppresses and delays melatonin production, your body’s natural sleep hormone. If you crawl into bed with the lights on, you may find it harder to fall asleep, especially if you’ve been exposed to bright light in the run-up to bedtime. 

The problems don’t end when you’re asleep, though. One small study found sleeping with the lights on was linked to an increased arousal index, a measure of how often you wake up during the night. Once you’re awake, having the lights on may make it harder to fall back asleep.

Not getting enough sleep can lead to sleep debt, which is how much sleep you owe your body. The more sleep debt you have, the more your energy, concentration, mood, and health will be impacted. Plus, you’ll be upping your odds of injuries and accidents as you’ll be more at risk of falling asleep while driving or while at work

You can learn more about sleep debt here.

RISE can work out how much sleep debt you have. This is compared against how much sleep you need — known as your sleep need. 

Sleep needs vary from person to person. When we looked at the sleep needs of 1.95 million RISE users 24 and up, we found it ranged from five hours to 11 hours 30 minutes. Almost half needed eight hours or more.

The RISE app can tell you how much sleep you need.
RISE users' sleep needs.

RISE users on iOS 1.202 and above can click view their sleep need here and view their sleep debt here.

Circadian Misalignment 

Your circadian rhythm is your roughly 24-hour biological clock. It takes cues from the light-dark cycle of the outside world. Light signals to your brain that it’s time to be awake, whereas darkness signals it’s time to be sleepy. 

Getting light at the wrong time can disrupt your circadian rhythm. For example, evening light can push back your circadian rhythm, making it harder to fall asleep on time. If you’re sleeping with the lights on, you’re probably spending your evenings with the lights on, too.  

This can cause circadian misalignment, which has been linked to impaired cognition and many health issues including cardiovascular disease, diabetes, and cancer.

Disrupted Sleep Stages 

Research from 2022 found light exposure during sleep affected participants’ sleep stages. They spent more time in light sleep and less time in deep sleep and rapid-eye-movement (REM) sleep. Another small study had similar findings.

During deep sleep, our muscles are repaired and immune systems strengthened, and REM is needed for creativity, memory consolidation, and emotional regulation. 

Weight Gain and Obesity

A 2019 study on almost 44,000 women found artificial light at night was linked to higher odds of obesity. That included sleeping with a small night light in the room, light outside the room, and a light or television on in the room.  

Compared to sleeping with no light, sleeping with the TV or a light on in the room was associated with gaining 11 pounds or more.

Changes in Heart Health 

Research from 2022 found just one night of sleeping in moderate light — defined here as 100 lux, which is darker than theater lighting — increased nighttime heart rate and decreased heart rate variability (a measure of heart health) compared to sleeping in a very small amount of light of less than 3 lux. 

This light wasn’t bright enough to suppress melatonin, but it may have activated the sympathetic nervous system — our fight-or-flight response — causing the adverse effects.

Type 2 Diabetes 

The same 2022 research found those sleeping with the lights on for one night experienced increased insulin resistance the next morning. Insulin resistance can lead to a whole host of health issues, including weight gain (especially belly fat), obesity, high blood pressure, and type 2 diabetes. 

Sleep research from 2023 on older adults found habitual exposure to light at night is linked to obesity, high blood pressure, and diabetes.  

Light from outside your bedroom may have this effect, too. A 2022 study found exposure to artificial outdoor light at night was associated with insulin resistance and diabetes. 

Mental Health Conditions 

A new study from 2023 found greater nighttime light exposure was linked to an increased risk of: 

  • Major depressive disorder
  • Generalized anxiety disorder 
  • PTSD 
  • Psychosis
  • Bipolar disorder
  • Self-harm behavior 
  • Poorer mood and well-being 

The brighter your light is, the higher your risk may be. Those who got the brightest nighttime light exposure had an about 30% increased risk for major depressive disorder and an about 20% increased risk for generalized anxiety disorder.

Any sleep loss you experience from light may also worsen mental health issues. 

But mental health issues, like feelings of anxiety and depression, may trigger sleeping with the light on in the first place, so more research is needed. 

Alzheimer’s Disease 

Research from 2023 highlights the many ways nighttime light exposure could be linked to Alzheimer’s disease. This included disrupting your sleep-wake cycle, gut microbiota, and brain’s electricity.

The researchers added these changes, among others, “may contribute to neurodegeneration and consequently Alzheimer’s disease.” 

And it’s not just bright light. Dim light at night “seems to be the most important type of light pollution that may contribute to neurodegeneration.” 

So even if you feel like you sleep fine, light could be messing with your sleep, and health, without you knowing it. 

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Does Sleeping With the Lights On Have Benefits?

Sleeping with the lights on may come with a few benefits. If you have anxiety or a fear of the dark, sleeping with the lights on may help you stay calm enough to drift off. 

It may also have benefits for older adults, helping to prevent falls and injuries if they get up in the middle of the night. 

However, research shows there are many health risks linked to sleeping with the lights on. 

If you need lighting at night, make it as dim as possible and consider a red light night light, which may be less disruptive to your sleep and circadian rhythm. We’ve covered more tips below. 

Expert tip: Taking a nap? You still want darkness. Napping with the lights on may make it harder to drift off. If you’re worried about oversleeping, set an alarm. 

Why Can’t I Sleep Without the Lights On? 

You might not be able to sleep without the lights on due to a fear of the dark — aka nyctophobia. Laying in the dark may cause fear, stress, and anxiety, which can make it hard to drift off. 

Turning out the lights may also worsen existing feelings of stress and anxiety. You might find it easier to relax with the lights on. You’re not alone if stress is keeping you up — RISE users say stress and anxiety are their biggest barriers to sleep!

If you’re used to sleeping with the lights on, you might feel anxious when you try sleeping with them off. This anxiety keeps you up, not the darkness. You may have developed a psychological dependence on having a light on to sleep, or sleep better with them on due to the placebo effect. 

It could also be due to something that has nothing to do with light at all, like poor sleep hygiene (more on that soon), being out of sync with your circadian rhythm, or a sleep disorder or medical condition. 

Although it’s not ideal, if you absolutely need a small night light for anxiety reasons, keep the light as dim as possible and consider putting it on a timer. Avoid bright and blue or cool-toned light in favor of a dim night light with a warm red or orange glow. More tips below.

We’ve covered how to sleep with anxiety here.

What to Do If You Can Only Sleep With the Lights On?

If you can only sleep with the lights on, there are small changes you can make to make light less damaging to your health. Try dimming the lights as much as possible, using a red light, and getting more light during the day, which makes you less sensitive at night.

Here’s what to do:  

  • Dim the lights: About 90 minutes before bed, dim the lights and put on blue-light blocking glasses. Make your bedroom as dim as possible and try gradually making it dimmer each night to get used to sleeping in the dark. 
  • Use red light: If total darkness triggers anxiety or you need light to get around at night, try a red night light night. Red light may disrupt your melatonin levels less than bright overhead lighting or blue light from screens. Although, brightness may make more of a difference — 2023 research found bright yellow light and dim blue light had the same effect on circadian rhythms, melatonin, and sleep. 
  • Use a timer: Research shows one hour of light exposure 30 minutes after bedtime can still push back your circadian rhythm, so aim to have the light on for as short a time as possible. If you need light when moving around at night, consider dim night lights on motion timers. 
  • Get light in the morning and daytime: Get out in natural light for at least 10 minutes as soon as possible after waking up. Then spend as much time in daylight as you can throughout the day. The more daylight you get, the less sensitive you’ll be to light come evening. Research shows bright light in the early evening can also have this effect. And 2023 research shows bright afternoon light until 5 p.m. was linked to an earlier sleep time, perhaps due to reduced light sensitivity in the evening. More research is needed to find out how much daylight you need, but one of our science advisors, Dr. Jamie Zeitzer, Co-Director of the Center for Sleep & Circadian Sciences at Stanford University, says it may be as little as an hour or two. 
  • Speak to a therapist about anxiety or a fear of the dark: Cognitive behavioral therapy or guided exposure therapy may help address the root cause of not being able to relax with the lights off.
  • Do a relaxing bedtime routine: Try reading, meditating, journaling, or taking a warm bath. This can help you unwind and feel calm enough to drift off in darkness. RISE can guide you through breathing and relaxation exercises to help you stay calm. We’ve covered more bedtime routine ideas here.
  • Wear an eye mask: An eye mask can reduce how much light gets into your eyes. This can be useful if you’re nervous about sleeping in a dark room, or if you can’t control your environment — like when bright street lights leak through the blinds (try blackout blinds!), or you’re trying to sleep on a brightly lit plane or in hospital. 
  • Improve your sleep hygiene: Sleep hygiene is the set of daily habits that help you fall asleep faster and wake up less often. Poor sleep hygiene can keep or wake you up, even in darkness. RISE can guide you through 20+ sleep hygiene habits, including when to get and avoid light, when to have your final coffee each day, and when to stop eating before bed.
RISE app screenshot showing sleep hygiene habit reminders
The RISE app can send you 20+ personalized sleep hygiene reminders.

RISE users on iOS 1.202 and above can set up their 20+ in-app habit notifications here

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Lights Off for Better Sleep   

Light is one of the most powerful cues we have to stay awake and fall asleep, and we need darkness to get the sleep our bodies need. Sleeping with the lights on can lead to trouble sleeping and a whole host of health issues. 

The RISE app can help you master your light and sleep. RISE can tell you when to get and avoid light each day, help you relax before bed if you find turning out the lights anxiety-inducing, and guide you through 20+ sleep hygiene habits to make a good night’s sleep possible.

All this can help you feel better each day: 

“This app has been life-changing. I’ve always been irresponsible with sleep but I wanted to see some change…The difference I feel in terms of energy is night and day.” Read the review

And it can happen fast — 80% of RISE users get better sleep within five days.

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