Two weeks without mobile internet: what 90.7 percent really means
In a randomized waitlist crossover study, 90.7 percent improved in at least one of three outcomes after their two-week intervention period: subjective wellbeing, mental health or objectively measured sustained attention. That does not mean 90.7 percent improved in all three. Here is what the researchers actually tested.
What exactly happened
Castelo and colleagues recruited iPhone users in the United States and Canada and randomly assigned when they would complete the intervention. Internet access on the phone was blocked over Wi-Fi and cellular data for two weeks. Calls and texts still worked, and participants could go online on other devices. The researchers measured wellbeing, mental health and sustained attention, the latter with an objective test.
The study started with 467 unique participants at baseline; 327 took part in the relevant follow-up waves and 119 were fully compliant with the block. That gap matters because completely cutting off mobile internet was difficult even inside a study.
The controlled comparison
During the first study period, a greater share improved in the intervention group than on the waitlist: 75 versus 47 percent for wellbeing, 68 versus 52 percent for mental health and 59 versus 46 percent for sustained attention. The attention difference narrowly missed the conventional statistical threshold in this comparison (p = .062).
What 90.7 percent actually means
In the pooled before-and-after responder analysis, 90.7 percent improved in at least one outcome. The corresponding shares were 73.3 percent for subjective wellbeing, 70.5 percent for mental health and 58.5 percent for sustained attention. The 90.7 percent figure is not a between-group causal effect and does not mean all three outcomes improved for each person.
Do you need to go offline for two weeks now?
No. The study tested a much more radical intervention than BACK TO CTRL. A practical interpretation is to protect selected windows instead of treating your whole phone as the enemy: a focused morning, an evening without the feed, a bedroom without automatic access. That is our product philosophy, not a product effect demonstrated by the study.
All numbers with source and year are in our research library.
Sources
- Castelo et al., Blocking mobile internet on smartphones improves sustained attention, mental health, and subjective well-being, 2025. doi.org