The study, published Tuesday in Frontiers in Psychiatry, looked at smartphone use among 1,043 students between the ages of 18 and 30 at King’s College London. Researchers asked the students to complete two questionnaires on their sleep quality and smartphone usage, in person and online.

Using a 10-question validated scale that was developed to assess smartphone addiction in children, nearly 40% of the university students qualified as “addicted” to smartphones, the study found.

“Our estimated prevalence is consistent with other reported studies in young adult populations globally, which are in the range of 30–45%,” lead author and King’s College medical student Sei Yon Sohn and her coauthors wrote in the study.
“Later time of use was also significantly associated with smartphone addiction, with use after 1 a.m. conferring a 3-fold increased risk,” the authors wrote.
Students who reported high use of cellphones also reported poor sleep quality, the study found. That falls in line with prior studies that have found overuse of smartphones at night to be associated with trouble falling asleep, reduced sleep duration and daytime tiredness. That’s likely because use of smartphones close to bedtime has been shown to delay circadian rhythm, the body’s normal sleep-and-wake clock.

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