JAMA Pediatrics: Smartphone Use After 10 p.m. Cuts Teenagers’ Sleep by 20 Minutes

The researchers analyzed data from 425 adolescents with an average age of around 15, covering nearly 7,600 nights. They found that on nights when participants spent more time than usual using their smartphones after 10 p.m., they had greater difficulty falling asleep on time and maintaining uninterrupted sleep.

The researchers also identified a relationship between phone use and sleep duration: every additional minute spent on a smartphone after 10 p.m., beyond an individual's usual average, was associated with later sleep onset and a shorter overall sleep duration.

According to Daniel Bigman, a child and adolescent psychiatrist and sleep medicine specialist, smartphone use not only takes up time that teenagers could otherwise spend sleeping but also keeps their brains active. Social media, videos, messaging, notifications, and screen light stimulate the senses and make it harder for the body to prepare for rest. Light can also affect the body's internal clock and the sleep-wake cycle.

The study found that sleep problems were associated not only with smartphone use after 10 p.m. but also with screen exposure in the 5–15 minutes before falling asleep. In these cases, teenagers were more likely to wake up during the night.

Insufficient sleep and frequent sleep disruptions can impair attention and concentration, increase irritability and anxiety, and heighten emotional reactivity. Teenagers may also experience daytime sleepiness, reduced motivation, and difficulty making decisions.

The researchers suggest that limiting smartphone use in the evening, particularly after 10 p.m. and immediately before bedtime, could improve adolescents' sleep quality. Experts advise parents not to threaten to take away their children's phones, but instead to encourage calmer activities before bed, such as reading, listening to music, relaxation exercises, or stretching.

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