Is Artificial Light at Night (ALAN) Affecting Your Sleep?

Sleep is an important part of your overall health. Sleep keeps your brain at peak performance and helps regulate mood. Getting too little sleep or low-quality sleep raises your risk of developing health conditions like heart disease, dementia, and obesity.¹

People with insomnia have trouble getting enough good sleep. Insomnia makes it hard to fall asleep and stay asleep. Research shows that artificial light at night (ALAN) and insomnia are linked. ALAN may increase episodes of insomnia. It can also impact many other aspects of your health.^1-3

What is artificial light at night?

ALAN is light pollution. For example, ALAN comes from outdoor sources like street lights, headlights, and lights on buildings. It also comes from indoor sources like electronics. Smartphones and other electronics with screens bombard us with ALAN. This is worrisome because ALAN has a lot of blue light. Blue light is a high-energy type of visible light.^4,5

Is insomnia affected by artificial light at night?

Scrolling through your phone before bed, for example, exposes you to a lot of blue light-emitting ALAN. Your brain then thinks it is daytime because that is when it sees the most blue light.^3,5

When your brain thinks it is daytime, your body stops releasing melatonin, a hormone that aids in sleep. In fact, a mere 8 lux of light can upset melatonin release. Lux is the measure of intensity of light, and 8 lux is about the brightness of a dimly lit hallway at night.^3,5

A 2024 study showed that ALAN causes poorer sleep quality and is linked to insomnia. As people were exposed to more ALAN, they had more insomnia. ALAN also has been shown to upset the circadian rhythm.⁶

What is a circadian rhythm?

The body runs on a 24-hour rhythm called the circadian rhythm. It tells your body when it is time to be awake and to sleep. The brain controls the circadian rhythm using light.
When you see bright lights, your body knows it should be alert and awake. When the sun sets and light dims, your body prepares for sleep. It releases melatonin, and important biological processes take place.^4,5

Seeing ALAN, especially blue light from screens, upsets the circadian rhythm. This makes it hard to fall asleep. It also lowers sleep quality and length of sleep. Disrupted sleep is linked to depression, diabetes, heart problems, and many other health problems.^3-5,7

ALAN and mental health

A 2023 study found a strong link not only between ALAN and insomnia, but also between ALAN and depression and anxiety. In the study, lots of exposure to ALAN caused a 20 percent increase in depression and anxiety symptoms. ALAN also raised the risk of:^2,3

• Post-traumatic stress disorder (PTSD)
• Psychosis
• Bipolar disease
• Self-harm

The study found that getting more daytime light exposure lowered the risk for these issues.^2,3

Many other studies have shown similar results. A 2020 study looked at the effects of ALAN on teens and showed that ALAN affected their sleep. Teens exposed to higher levels of ALAN slept 11 minutes less than those exposed to lower levels of ALAN. These teens also went to bed 29 minutes later. More ALAN also raised their risk for mood disorders and anxiety.⁸

Lifestyle changes that can help

Along with mental health problems, ALAN has been linked to problems with hormone secretion, metabolism, higher-weight bodies, and some cancers. But there are ways to lessen the impact of ALAN:^3-6,8

• Do not look at bright screens for 2 to 3 hours before you go to bed.
• Get plenty of sunlight during the day.
• Use dim red lights as night lights. They do not affect circadian rhythm.
• Use blue light-blocking filters on glasses and electronics.
• Use dimmer switches on household lights.