Screen time is the amount of time spent using a device with a screen such as a smartphone, computer, television, video game console, or a tablet. The concept is under significant research with related concepts in digital media use and mental health. Screen time is correlated with mental and physical harm in child development. The positive or negative health effects of screen time are influenced by levels and content of exposure. To prevent harmful exposure to screen time, some governments have placed regulations on its usage. Since their popularization in 2007, smartphones have become ubiquitous in daily life. In 2023, 85% of American adults reported owning a smartphone. An American survey in 2016 found a median of 3.7 minutes per hour screen use per citizen. All forms of screens are frequently used by children and teens. Nationally representative data of children and teens in the United States show that the daily average of screen time increases with age.TV and video games were once largest contributors to children screen time, but the past decade has seen a shift towards smart phones and tablets. Specifically, a 2011 nationally representative survey of American parents of children from birth to age 8 suggests that TV accounted for 51% of children's total daily screen time, while mobile devices only accounted for 4%. However, in 2017, TV dropped down to 42% of children total daily screen time, and mobile media devices jumped up to 35%.

Effects of Screen Time

1. Sleep

More screen-time has been linked with shorter sleep duration, decreased sleep efficiency, and longer sleep onset delay. When using any screen before bedtime, the blue light emitted disrupts the body natural melatonin hormone production. Melatonin is produced by the brain's pineal gland and controls the body internal clock. This clock is what is referred to as the body circadian rhythm and it naturally is responsive to light. Melatonin levels increase as the sun sets and remain at that increased state for the remainder of the night. As the sun rises, melatonin levels start to drop. This hormone reduction is what helps the body natural rhythm wake up due to the bursts of natural sunlight. The light screens emit are in a similar spectrum of sunlight, but the blue light emission is what human circadian rhythms are most sensitive to. Studies have shown that the blue wavelengths are closely correlated to those from sunlight, which is what helps the body keep in sync with the sunrise and sunset. Therefore, using any screen prior to bedtime disrupts the body production of natural bedtime hormones which can trick the brain to believe it is still daytime making it harder to fall asleep.

2. Brain Development

An increase in screen time has been associated with negative cognitive outcomes for children between 0 and 4. A study on Korean children aged 24–30 months old found that toddlers with 3 hours of TV viewing per day were three times as likely to experience a language delay. Toddlers with higher TV time also scored lower on school readiness tests, which measured vocabulary, number knowledge, and classroom engagement. The same outcomes are not present in children older than 4. Children who watched more TV were found to have less brain connectivity between language, visual and cognitive control regions of the brain than their peers who watched less TV.

3. Behavioral impact

Screen use has been implicated with a slew of behavioral effects, especially in children. The primary effect is an increase in sedentary activity. Approximately 47% of American children spend 2 or more hours per day on screen-based sedentary activities. Research results indicated children who had high amounts of screen time had delayed white matter development, decreased ability to rapidly name objects, and poorer literacy skills. It has been proven that there is a negative relationship between increase screen time and behavioral problems in young children. In these preschool aged children (between the ages of 0-5 years old) with over four hours of screen usages a day was shown to have 1.76 times more likely to have behavioral and conduct problems. This is in contrast with the 25.5% who reported at least 20 minutes of physical activity per day for a week. Additionally, the likelihood of a child participating in physical activity has been shown to decrease with increasing screen use. Screen use can also affect interpersonal skills.

4. Language Development

Children that spend an increased amount of time on screens have less opportunities to interact with adults and caregivers which reduces their language development. Language skills is an essential part of early childhood development, and human interaction is the best way for these children to develop those skills. When children are spending most of their time using tablets and screens there are less chances for them to interact with adults, like their parents, to expand their language skill set. It has been shown that younger, preschool aged children and the amount of screen time they are exposed to has a negative effect on their language development. When these children are spending 2 or more hours on their screens, tablets, TVs it is more likely for them to have a poor vocabulary and shows delays in when they are starting to speak.

5. Academic Performance

Academic performance can be improved by screen time depending on the length and content of exposure. Toddlers after the age of 18 months can be exposed to high-quality programming such as Sesame Street or PBS that provide educational television. The right content can prove beneficial, but too much screen time distracts students from studying. It is important for parents to establish a limit to how much screen time their children can use per day. Limiting and monitoring children screen usage can increase cognitive development, but further research is required to get a better understanding of how screen time positively affects academic performance. On the other hand, increased screen use has been associated with missing school assignments. Students who used screens for more than two hours a day are twice as likely to not turn in homework on a regular basis. It is yet to be proven that screen time can significantly enhance academic performance, but it is known that increased use in screen time distracts students from focusing on class assignments.