Screen time

Screen time is the amount of time spent using an electronic device with a display screen such as a smartphone, computer, television, video game console, or 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 on a particular individual are influenced by levels and content of exposure. To prevent harmful excesses of screen time, some governments have placed regulations on usage.

The first electronic screen was the cathode ray tube (CRT), which was invented in 1922. CRTs were the most popular choice for display screens until the rise of liquid crystal displays (LCDs) in the early 2000s. Screens are now an essential part of entertainment, advertising, and information technologies.

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's 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's total daily screen time, and mobile media devices jumped up to 35%.

Research has shown that race and socioeconomic class are associated with overall screen time. Younger demographics and individuals who self-identified as Black and "Other" were associated with above average screen use. Additionally, Black and Latino Americans had longer screen times because of less access to desktop computers, which thus leads to more time on phones. In children, the divide is much larger. On average in 2011, White children spent 8.5 hours a day with digital media, and Black and Latino children spent about 13 hours a day on screens. Black and Latino children were also more likely to have TVs in their rooms, which contributed to their increased use of screen time.

The discrepancy in the amount of screen time can also be attributed to a difference in income. In more affluent private schools, there has been a larger push to remove screens from education in order to limit the negative impacts that have been found from screen time. However, in public schools there is more push for the use of technology with some public schools advertising free iPads and laptops to students. Additionally, affluent families are able to afford nannies and extracurriculars that can limit the need for entertainment from screens.

The COVID-19 pandemic in 2020 increased screen time as people stayed indoors, adding to concerns about the effects of excessive screen time. Specialists called for limiting screen time and for living a more active lifestyle. Studies have shown that even after children returned to school following a period of online schooling, which significantly increased daily screen time, their level of physical activity has remained low, while screen time has increased. Due to the increase of screen time, many children gained weight during this time.

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's natural melatonin hormone production. Melatonin is produced by the brain's pineal gland and controls the body's internal clock. This clock is what is referred to as the body's 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's 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's production of natural bedtime hormones which can trick the brain to believe it is still daytime making it harder to fall asleep.

Increased use of screens in children has also been shown to have an association with adverse effects on the quality of sleep in children. A 2010 review concluded that "the use of electronic media by children and adolescents does have a negative impact on their sleep, although the precise effects and mechanisms remain unclear", with the most consistent results associating excessive media use with shorter sleep duration and delayed bed times. A 2016 meta-analysis found that "Bedtime access and use of media devices was significantly associated with inadequate sleep quantity; poor sleep quality; and excessive daytime sleepiness". This relationship is because much of the time spent on screens for children is at night, which can cause them to go to sleep later in addition to the blue light from the screens making it more difficult to sleep.