In a study following 9,398 young people aged 11–12, bedroom devices and leaving a phone ringer on overnight were associated with shorter sleep a year later. The study measured specific bedtime behaviours, rather than treating every hour of use as equivalent.
What this means
Timing and interruptions may matter more than a daily total alone. This prospective study supports concern, but does not prove that the phone caused the sleep outcome.
Where the evidence stops
Phone behaviours and sleep duration were self-reported; sleep disturbance was caregiver-reported. Other influences may remain despite statistical adjustment.
02 / Attention & learning
Smartphone use in the classroom
Experimental · context-specific
Two randomized experiments at a vocational school in China compared banned, unrestricted and teacher-guided smartphone use. Unrestricted access reduced learning gains; using phones for a specific teaching task improved them.
What this means
Purpose and setting matter. This is stronger evidence for those classroom conditions, not proof that every phone ban improves every school outcome.
Where the evidence stops
The experiments used particular language lessons and a dictionary app, with students aged 14–23. They did not establish long-term effects across all subjects or age groups.
03 / Mood & wellbeing
Social media use and wellbeing
Association · causal limits
A review of 143 studies examined social-media use alongside anxiety and depressive symptoms in adolescents. It reported associations, with limited evidence from clinical populations. Observational studies cannot settle whether use leads to distress, distress changes use, or other factors influence both.
What this means
Notice the experience as well as the minutes: the content, interactions and circumstances of use. Evidence about social media should not be treated as evidence about every smartphone activity.
Where the evidence stops
A 2026 correction addresses an effect-size error in the review. The correction is linked beside the paper; numerical effect estimates are omitted from this edition.
04 / Online safety
Support for online bullying
Child-safety guidance
Repeated threats, humiliation or harassment online can affect wellbeing and make people feel unsafe. UNICEF advises involving a trusted adult, using reporting and blocking tools, and keeping a record of what has happened where it is safe to do so.
What this means
Treat the specific harmful behaviour seriously. Reducing total phone time alone does not resolve harassment.
Where the evidence stops
Reporting routes and platform tools vary. This is general guidance, not an assessment of an individual situation.
05 / Hearing & sound
Sound exposure and hearing
Established risk · sound exposure
Loud sound can damage hearing. Risk depends on sound level, duration and how often exposure occurs. The World Health Organization recommends lower volume, listening breaks and using sound-exposure monitoring where available.
What this means
Time and volume belong together. A phone is one way to deliver sound; these risks also apply to other listening devices.
Where the evidence stops
A volume percentage is not an exact sound dose across all devices and headphones. Individual settings and environments differ.
06 / Road safety
Phone use and driver distraction
Established road-safety concern
The World Health Organization identifies phone use as a source of driver distraction. It slows reactions and interferes with keeping position and distance. Hands-free calling does not remove the cognitive distraction.
What this means
The concern is the driving situation and divided attention, not a daily screen-time threshold.
Where the evidence stops
This evidence concerns driving. It should not be used as a numerical estimate for every activity involving a phone.
07 / Data privacy
App permissions and personal data
Data-protection guidance
Apps can request access to location, photos, contacts, camera and microphone. CNIL explains that permissions control technical access; they do not, by themselves, explain every purpose for using the data or always constitute valid consent.
What this means
Consider what a feature needs, what data it requests and who receives them. Contact lists and shared photos can also expose other people’s information.
Where the evidence stops
Permissions do not cover every data flow. Platform controls differ, and restricting access does not necessarily delete information already collected.
Brain studies help examine responses to social feedback and phone-related cues. In a laboratory Instagram task, adolescents responded more strongly to popular photos in regions involved in reward and attention. This does not measure a dopamine surge or diagnose addiction.
What this means
A three-year study of 169 adolescents associated habitual social-media checking with different changes in brain responses to anticipated social feedback. It does not establish that checking caused harm or brain damage. A 2023 figure correction is linked with the study.
Where the evidence stops
These studies examine specific tasks and groups. Brain-activity patterns are not a diagnosis, and findings about social media should not be applied to every smartphone activity.
Dopamine and serotonin: what was measured?
Dopamine and serotonin are chemical messengers with several functions. Dopamine contributes to learning, movement and emotions; serotonin influences mood, sleep and digestion. A brain scan showing activity is not a direct reading of their levels.
The 72-hour restriction study
In a 2025 study, 25 young adults were scanned before and after 72 hours of smartphone restriction. Changes in responses to phone images were associated with reference maps for dopamine and serotonin receptors. The study did not directly measure either chemical in participants.
Limits of this study
The sample was small, there was no unrestricted comparison group, and adherence was not independently verified. Receptor-map correlations do not establish chemical depletion, a brain reset or a treatment effect.
When does a habit become a concern?
Frequent use alone does not establish addiction. WHO’s gaming-disorder criteria concern impaired control, priority over other activities and continued gaming despite negative consequences, with significant impairment. Those criteria describe gaming, not every use of a phone.
Topic sources checked · 28 October 2026
Safety guidance
Online abuse and phone use while driving
Threats or online abuse
Involve someone you trust. Use reporting tools and seek immediate help if you are in danger.
A randomized adult trial found improvements in sustained attention and reported wellbeing after a two-week mobile-internet block. Participants were mostly motivated to reduce use, and adherence was difficult. It does not establish the same benefit in teenagers or from every lighter-touch change.
Tristan Harris examines how digital products compete for attention. A design-ethics perspective—not a clinical study or proof of every claim about health.
TED · 16 min 51 sec · English; transcript and language options on TED.
The explorer currently contains 4 sources, 15 attributed statements and 12 measurements. It is a separate, dated sample—not the full source set used in these briefs.
The collective behind this initiative
noeo collective
νοέω· noéō
Greek: to perceive, understand and think.
Bringing knowledge, perspectives and people together.
Privacy, consent & age
What does “I agree” mean?
Terms of service
Accepting terms creates an agreement about using a service. Check account rules, content licences, payments and termination. A privacy notice explains data practices; accepting terms is not blanket consent to every use of your data.
Phone permissions
Allowing camera, contacts or location grants technical access. Ask whether the feature needs it, whether access continues in the background, and what happens to data already uploaded when permission is removed.
Consent to data use
Under the GDPR, consent must be freely given, specific, informed and unambiguous. Optional purposes need meaningful choices, and withdrawing consent must be as easy as giving it. Some processing uses other legal bases, such as a contract or legal obligation.
Before agreeing, check five things
What data? For which purposes? Shared with whom? Kept for how long? How can I refuse, withdraw, access or delete it? Look for advertising, profiling, contact uploads, location history and AI-related uses where the notice describes them.
Seven social, messaging and video apps to explore. Select an app for privacy links and age rules; this is a selected catalogue, not a popularity ranking.
Age rules are not a safety rating. The optional check compares an age with the selected app’s rules; it never hides apps from the list.
Check age rules for a person (optional)
Select an age only if you want to compare it with these rules. No date of birth or identity document is needed.
Why these limits?
Providers set account and feature rules to support age-appropriate experiences and meet legal obligations. These thresholds are not proof that an app becomes safe at a birthday.
An app-store age rating describes content suitability. It is separate from account eligibility, consent law and feature restrictions.
Android trackers and permissions. Reports apply to a specific version; detected code does not prove active tracking or cover every tracker. They do not assess iOS.
Privacy-policy evaluations with a focus on children and education. Ratings are not legal eligibility decisions.
Who can help?
noyb works on enforcing European privacy rights. A national data-protection authority can explain rights and receive complaints. These roles differ from an app-rating database.
Choices stay in this page’s memory and are not sent to a database. External sites are contacted only when you open their links. Rules checked: 28 October 2026; they may change.
About this project
About Smartphone Awareness
Smartphone Awareness brings research and practical guidance together to support informed choices about technology. This edition focuses on young people, families and schools.
Smartphones, social media, gaming and general screen use involve different activities and experiences. Each summary identifies who was studied and distinguishes associations, experimental findings and professional guidance.
An initiative of noeo collective, grounded in care, human dignity and respect for nature. The Knowledge Mapping Framework (KMF) supports the evidence methods. Sources and methods guide the conclusions.