person on phone
© Paul Hanaoka/ Unsplash
A month-long randomized control trial confirms that reducing the time spent on smartphones to access the internet makes people happier and more focused.

On average, Americans spend almost five hours a day using their smartphones, and half of Americans who use smartphones worry they use their devices too much. Noah Castelo and colleagues sought to determine whether constant access to the Internet through smartphones harms cognitive functioning and mental health. Their results are published in PNAS Nexus.

The authors recruited 467 participants from Prolific.co, an online labor pool, to install an app on their iPhones that blocked all internet access on their phones. Half the participants had their phones blocked for the first two weeks, during which time the other half of participants functioned as a control. The groups switched treatments for the second two-week period.

mobile phone study
Attention, mental health, and SWB improve after 2 weeks of blocking mobile internet. In the Intervention group, participants blocked mobile internet access from T1 to T2. In the Delayed Intervention group, participants blocked mobile internet access from T2 to T3. Credit: PNAS Nexus (2025). DOI: 10.1093/pnasnexus/pgaf017. https://academic.oup.com/pnasnexus/article/4/2/pgaf017/8016017
Participants found the experiment difficult. Of the 467 who agreed to install the app, just 266 did so and just 119 had the block active for at least 10 days. Blocking the internet reduced screen time from an average of 314 minutes a day to 161 minutes a day and created significant improvements in subjective well-being, mental health, and objectively measured sustained attention ability.

The change in sustained attention ability was equivalent to erasing 10 years of age-related decline and the improvement in symptoms of depression was larger than the average effect of pharmaceutical antidepressants. Notably, for the group who blocked the internet for the first two weeks, subjective well-being and mental health remained significantly higher at the four-week mark, even after two weeks of being back online.

The authors attribute the positive effects of disconnection to increased time spent in the offline world, decreased time spent consuming media, increased social connectedness, improved feelings of self-control, and increased sleep. According to the authors, spending less time with a connected device may benefit many people.

More information: Noah Castelo et al, Blocking mobile internet on smartphones improves sustained attention, mental health, and subjective well-being, PNAS Nexus (2025). DOI: 10.1093/pnasnexus/pgaf017. academic.oup.com/pnasnexus/art ... /4/2/pgaf017/8016017

Journal information: PNAS Nexus