phone offline window
This identifier was used as an evidence-review target but was never published as a canonical Brali protocol. It is retained as provenance and deliberately does not link to a public route.
Evidence Ledger · Protocol candidate · reviewed 2026-08-27
Blocking mobile internet on smartphones improves sustained attention, mental health, and subjective well-being
The reviewed source can support a conservative practical protocol.
Brali decision: Protocol candidate. This page summarizes a reviewed evidence boundary; it does not reproduce the source and it does not turn one paper into a universal prescription.
What the source supports
For adults who actively want to reduce constant phone connectivity, temporarily removing mobile-internet access from the phone is a defensible attention experiment. In this randomized trial, the intervention produced a small intention-to-treat improvement in objectively measured sustained attention while calls, texts and non-phone internet remained available. Brali can therefore test a bounded phone-offline window or period when the user's goal is fewer digital temptations and more sustained attention.
What it does not establish
- Blocking mobile internet treats depression, anxiety, ADHD or any mental-health condition.
- Two weeks is an optimal or necessary duration.
- Everyone should use a dumb phone or eliminate smartphone internet.
- A fixed daily screen-time threshold is scientifically established by this study.
- The intervention will improve productivity, job performance or learning outcomes.
- The self-reported wellbeing effects are free from expectancy or demand effects.
- The study proves that every notification, app or form of internet access is harmful.
Important limitations
- Only 119 of 467 participants who agreed to the intervention met the preregistered compliance threshold, so the full two-week block was difficult to sustain.
- The sample was strongly motivated to reduce smartphone use, which limits generalizability to people who do not share that goal.
- Only 67 percent completed all three surveys; completers had somewhat better baseline mental health and sustained attention than non-completers.
- The delayed-intervention design did not provide an active placebo control, so expectancy and demand effects may have affected self-report outcomes.
- The sustained-attention task provides a cognitive outcome, not direct evidence of improved work, study, safety or life performance.
- The study tested a broad mobile-internet block, not shorter work windows, app-specific limits, notification batching or other lower-friction variants.
Source context
Blocking mobile internet on smartphones improves sustained attention, mental health, and subjective well-being
- Source type: primary-study
- Design: Preregistered month-long randomized controlled delayed-intervention trial. Participants were randomized to block all mobile internet on their smartphone during the first or second two-week phase. The Freedom app objectively tracked whether the block was active. Main analyses were intention-to-treat.
- Population: 467 unique adult participants in the United States and Canada who agreed to attempt a two-week mobile-internet block. The sample was strongly selected toward people motivated and confident about reducing smartphone use; retention to all three surveys was 67 percent.
- Exposure / intervention: Block all Wi-Fi and mobile-data internet access on the smartphone for two weeks while preserving calls and text messages and allowing internet access from other devices such as computers or tablets.
- Outcomes: Objectively measured sustained attention on the gradCPT; Subjective wellbeing; Self-reported mental-health composite; Smartphone screen time; Time-use mediators
Citation: Castelo N, Kushlev K, Ward AF, Esterman M, Reiner PB. PNAS Nexus. 2025;4(2):pgaf017.
DOI: 10.1093/pnasnexus/pgaf017
What this changes in Brali
Editorial note: Protocol direction: when a user identifies phone connectivity as a recurring attention conflict, preserve essential communication but remove the internet channel from the phone for one bounded, user-chosen period. Measure actual phone use and completion/focus on the intended task. Start with a lower-friction window rather than prescribing the study's two-week block; escalate only if the user wants to test a stronger version. Stop or redesign the experiment if access is needed for safety, care, work authentication, navigation or other essential functions.
Use the boundary, not just the headline
When an AI agent or a person retrieves this decision, preserve both the supported claim and the unsupported or overstated claims. Dropping the boundary would turn a reviewed source into a stronger claim than Brali actually maintains.
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