It starts the moment my phone’s alarm app buzzes in the morning — the urge to check messages and scroll through notifications even as my conscious brain is barely awake. 

The same device that jolts me awake in the morning is often the last thing I see before drifting off to sleep at night. Whether it’s to watch one last video, finish a late-night study session or reply to a friend’s texts, I am one of millions of teens who have integrated screens into my bedtime routine. 

But at what cost?

As comforting as our nightly screen habits may seem, it is a daunting, yet undeniable truth that using screens before bed disrupts the body’s natural sleep-wake cycle. By keeping us engaged with the array of apps on the screen, phones during late night hours are one of the main reasons most teens fail to get a fully restful night’s sleep. 

According to the CDC, the recommended amount of sleep for high school students is at least 8 hours each day. However, its annual Youth Risk Behavior Survey reveals that during 2023, a striking 77% of high school students got less than 8 hours of sleep on an average school night. 

 
The sleep-wake cycle is regulated by your biological clock

All humans have a circadian rhythm — a biological clock that follows a 24-hour sleep-wake cycle dictating when you feel drowsy or alert. It encompasses not only physical feelings, but also mental and behavioral changes experienced throughout the day. This biological rhythm also affects several systems in the body, including digestion and temperature regulation. But while your brain dictates circadian rhythms, external factors can easily influence them. 

Because every tissue and organ in the body has its own circadian rhythm, this biological clock becomes particularly sensitive to outside factors — a disruption in one area can easily affect the entire system. 

Although circadian rhythms influence various integral functions in the human body, one of the most significant is their role in stimulating sleep-related hormones. When the sun rises, the body produces cortisol, a hormone that makes you feel awake and alert. Conversely, as daylight fades, the body releases melatonin, a hormone that produces a sense of sleepiness. This is where screens can be a complicating factor.

 
Electronic devices emit “blue light,” which affects hormone release

Electronic devices such as cell phones, tablets and computers emit short-wavelength enriched light, also known as blue light. Fluorescent and LED lights, which illuminate billions of houses across the globe, also emit blue light; all of these sources have been shown to reduce or delay the natural production of melatonin in the evening and decrease feelings of sleepiness. 

According to Eye Care Center West, blue light can also reduce the amount of time the body spends in slow-wave and rapid-eye movement (REM) sleep, two stages of the sleep cycle that are vital for cognitive functioning.

While exposure to blue light is important for maintaining well-being, alertness and cognitive performance during the day, constant exposure directly before bedtime may have serious implications on the circadian phase and cycle durations. In fact, exposing the eyes to blue light during the sensitive periods of the rhythm, such as in the morning and evening, triggers photoreceptors in the retina to signal the suppression of melatonin and to shift your internal clock — according to the National Institute for Occupational Safety and Health.

With a disrupted rhythm, people commonly experience trouble falling asleep, difficulty staying asleep, sleepiness during the day and headaches.

One of the most prominent examples of a shifted circadian rhythm is the well-known phenomenon of jet lag — the disorienting feeling after a long flight where your body may insist it’s the middle of the night even though it’s midday. In the same way that jet lag is a circadian rhythm disorder, so is a shifted rhythm, caused by use of electronics before sleep.

A study researching the relationship between screen media habits and sleep published in the National Library of Medicine has established a trend between screen time before bed and an increase in sleep latency, or the amount of time it takes to fall asleep. In one example, people using an ebook before sleep took, on average, nearly 10 minutes longer to fall asleep than those reading physical books. This increased sleep latency is associated with disturbed sleep, manifesting in night awakenings and decreased sleep depth — in other words, your sleep quality goes down.

Blue light also impacts sleep in areas besides minimizing melatonin production. In 2021, Yamagata College found that blue-light exposure affects sleep quality by reducing the ratio between time in deep sleep to total sleep length. Playing a vital role in various bodily functions, deep sleep is one of the most crucial stages of a night’s rest. During this phase, the body makes physical repairs, strengthens the immune system, consolidates memories and clears metabolic waste. Deep sleep also helps regulate hormones while allowing the heart and mind to experience a period of reduced activity.

Not only does blue light exposure make it even more difficult to fall asleep and wake up the next day, studies conducted by the Vision Council have also shown that exposure to blue light can cause damage to your retinas. Staring at screens can lead to computer vision syndrome, a condition causing eye fatigue, dry eyes and blurred vision, which affects 75% of people who work on computers.

One main cause of computer vision syndrome is the tendency for people to have a decreased blinking rate when they are concentrating. Specifically, when using a computer, research has found that people blink 66% less often than they typically would. Glare and reflection off your monitor — whether it be from overhead lights, task lamps or even the sun shining through the window — can also make the muscles in the eyes tired.

Moreover, blue light exposure can also put the eyes at risk of age-related macular degeneration (AMD). The risk of AMD, an eye disease that causes vision loss, is increased by blue light when it triggers the release of toxic molecules in photoreceptor cells, inflicting damage on your eyes. Symptoms of this disease include blurry vision and potentially loss of central vision, which is necessary for everyday activities such as driving, reading, recognizing faces and performing close-up work.

Computer monitors, separate from laptop screens, pose yet another harmful side effect on your eyes. Since the refresh rate of many monitors is only 60 Hz, the speed can cause a visible flicker that makes the screen appear to roll. The flicker stimulates the eye to refocus repeatedly, tiring the visual system.

 
Electronic devices can harm sleep in ways beyond blue light exposure

Even before bedtime, using devices for longer periods of time during the day can also reduce sleep quality and length. A large population-based study by researchers at University of Bergen, measuring the amount of sleep and length of screen use of nearly 10,000 adolescents in Norway concluded that increased time spent using electronic devices decreased sleep duration and increased long sleep onset latency and sleep deficiency. 

Blue light in device screens isn’t the only cause for people’s sleep struggles at night — looking at phones during this time increases brain alertness and activity, which are the opposite factors for what you need for sleep. A habit that became famous during the pandemic, Doomscrolling, or consumption of social media for extended hours, can distract you for long periods of time, keeping you awake and delaying REM sleep. 

Even just a quick phone check can engage your brain and delay sleep. As a result, your mind can stay active and engaged, long after you’ve scrolled through social media or responded to a few emails. Moreover, it’s not just the alertness you get from late-night social media sessions either. It’s thinking about or feeling your phone going off under your pillow and the subconscious habit of expecting messages that makes it harder to fully relax and fall asleep.

This can be explained with the psychological effect called phantom vibration syndrome (PVS). Also known colloquially as “ringxiety,” PVS causes people to think their phone is ringing or vibrating from a text message when it actually is not. A study remarkably found that nearly 89% of its participants experienced this at least once every two weeks. 

According to a study in Computers in Human Behavior, trouble falling asleep is connected to PVS through the idea that our general relationships with devices lead to significant levels of anxiety. The author, Robert Rosenberger, also suggests that we get “anxious as we wait in high anticipation for the next email, social media post, phone call or text message.” Suppressed melatonin, in conjunction with this lingering sense of anxiety and anticipation, invokes restlessness, delaying the onset of sleep.

While using social media late at night media, it’s also possible that people encounter content that causes intense emotions. Running into emotion-evoking content can cause stress and anxiety, which are two major reasons for disrupted sleep, according to Sleep Foundation. Even seeing something right before bed that makes you happy can trigger a response that prolongs falling asleep. 

Following this, a cycle may occur when excess worry and stress make it harder to fall asleep and stay asleep through the night; sleep deprivation worsens anxiety, spurring a negative cycle involving insomnia and anxiety disorders.

Finally, your device itself may entice you to stay awake for longer. Phones and tablets by Apple, Google and other companies are built to keep you drawn in — algorithms are designed to captivate your attention and keep you using apps longer. So that “one last video” often becomes 10 or 15, pushing your bedtime later and later. 
 
What are some healthy habits to increase sleep quality?

One useful technique to prevent digital eye strain anytime during the day is to follow the 20-20-20 rule — taking a 20-second break to view something 20 feet away every 20 minutes to alleviate stress on the eyes. It takes about 20 seconds for your eyes to completely relax, which is a healthy practice to reduce eye strain. While you’re resting your eyes, it’s also a good idea to get up and grab a drink of water to keep yourself hydrated, as keeping your body hydrated will allow your eyes to be as well.

Tucking your devices away for the night an hour or two before bed is also a good rule, creating a more conducive environment for restful sleep. However, this may not be an option for many teens as they study late into the night. In such cases, decreasing your daytime electronics use in general is always good to stand by.

Additionally, a regular bedtime routine that ensures an adequate amount of rest is essential for healthy sleep. The hour before bed should consist of activities that not only relax your body before sleep, but also distract you from your devices — ones like reading a physical book or taking a hot bath or listening to music.

Another good practice if you must use your phone at night is to use the Night Mode function. This setting reduces blue light emissions and decreases the display’s brightness setting. On the same note, some phones also have blue light filters, which adjust the color temperature of the screen to warmer tones.

Investing in blue light blocking glasses, which have been proven to be effective, is another option. These glasses filter out the blue light and are able to protect your retinas. 

The bottom line is that excessive screen use can upset the body’s natural sleep-wake rhythm. When you repeatedly sleep less hours than your body needs, you risk accumulating sleep debt which, over time, can have negative mental and physical impacts.

 So, the next time you find yourself scrolling through an endless feed of memes, cat videos or just the never-ending abyss of social media reels, remember that your phone is not just keeping you entertained — it’s keeping you awake. It’s a good idea to put the phone down a bit earlier, allowing your mind to unwind and get some rest before the next day ahead. After all, your brain and body will thank you in the morning.