LOCKSTA BLOG

Smartphone Addiction in Teenagers: How to Spot the Signs – and What Schools and Parents Can Do Now

9 min

“Smartphone addiction” – a term science doesn’t actually use

First, an important point of clarification, because it changes how we see the issue: “smartphone addiction” is not a medical diagnosis. The international classification ICD-11 (in force since 2022) recognises only gaming disorder and, more broadly, internet-related disorders. Otherwise, experts speak of problematic, risky or pathological media use.

This is not mere semantics. It means: not every teenager who spends a lot of time on their smartphone is “addicted.” At the same time, the underlying problem is real, measurable – and growing.

How widespread is problematic media use really?

The most robust figures for Germany come from the longitudinal study “Mediensucht” run by DAK-Gesundheit together with the University Medical Center Hamburg-Eppendorf (UKE), which has surveyed around 1,000 families with children aged 10 to 17 every year since 2019.

The results of the most recent survey wave (conducted in autumn 2025):

6.6% of 10- to 17-year-olds show pathological, i.e. addictive, social media use – extrapolated, that is around 350,000 children and adolescents in Germany. Compared with the previous year, that is an increase of 1.9 percentage points.
21.5% use social media in a risky way – more than one million young people.
For video streaming services, around 4% meet the criteria for dependency.

For comparison: the BZgA (German Federal Centre for Health Education) already found in 2019 that 8.4% of 12- to 17-year-olds met the criteria for a gaming- or internet-related disorder – more than double the figure for 2011.

The devices themselves have long been part of everyday life: according to the JIM Study 2025 by the Medienpädagogischer Forschungsverbund Südwest (mpfs), 95% of 12- to 19-year-olds own a smartphone. The average daily time spent online is 231 minutes – almost four hours, and rising again.

Context: The figures vary depending on the type of media (social media, gaming, streaming) and the survey year. A reputable figure always comes with a source and a year. What holds true across all studies: a substantial share of teenagers use smartphones to an extent that experts classify as risky – and that share is rising.

How do I recognise problematic use? The warning signs

Whether intensive use has turned into a problem that needs treatment cannot be read off the sheer number of hours. What matters is the balance with the rest of life. The German S3 guideline “Internet-related disorders” (published by the German Society for Addiction Research and Addiction Therapy, as of November 2024) names these core features, based on ICD-11 and DSM-5:

The three core symptoms (per ICD-11)

Loss of control over when use starts, how long it lasts and when it ends.
Increasing priority given to the smartphone over other interests and everyday responsibilities.
Continued use despite negative consequences – use carries on even though it is demonstrably harmful.

Concrete warning signs in everyday life (per DSM-5)

Strong mental preoccupation – the phone is constantly present, even offline.
Irritability, restlessness or nervousness when the device is unavailable.
Needing ever more time to achieve the same “good feeling.”
Unsuccessful attempts to cut down use.
Neglect of former hobbies, friendships and responsibilities.
Concealing the true extent of use from parents and teachers.
Using the phone as an escape from bad feelings, stress or boredom.

Important: This list is a guide, not a diagnosis. If several points apply over a longer period and cause genuine distress, professional help is the right path – for example through the Fachverband Medienabhängigkeit e. V., a family counselling service, or the BZgA self-test at ins-netz-gehen.de.

Which consequences are proven – and which are not?

This calls for scientific honesty. Most findings are correlations, not proven cause-and-effect relationships: high use goes hand in hand with poorer scores – but whether the smartphone is the cause, or whether already-burdened teenagers reach for the smartphone, often cannot be clearly deduced from this.

With that caveat, the research shows:

Sleep: in the JIM Study 2025, around 30% of teenagers report often being tired in the morning because they reach for their phone too late at night. The blue light of displays also suppresses melatonin release and delays falling asleep.
Concentration: a longitudinal study by the University of Vienna (384 parent-child pairs, children aged 10 to 14) found that night-time smartphone use in particular has a negative effect on perceived cognitive attention.
Mental health: the DAK/UKE study 2025 reveals a worrying new trend: more than 30% of teenagers with depressive symptoms use AI chatbots to cope with loneliness and negative feelings – compared with around 10% on average.

The uncomfortable finding: bans alone are not enough

Precisely because we are a company that enables phone-free learning environments, this point matters to us – honesty beats marketing:

The most extensive study to date on school phone bans (SMART Schools, University of Birmingham, published in The Lancet Regional Health – Europe on 5 February 2025, 1,227 pupils across 30 schools) found no measurable difference between schools with and without a phone ban – neither in wellbeing nor in sleep, physical activity or grades.

The reason is revealing: the ban only reduced use during school hours (around 40 minutes less phone use, 30 minutes less social media), but not total daily use of 4 to 6 hours. At the same time, the same study confirms: high total use is clearly associated with poorer scores.

The researchers’ conclusion: what is needed are approaches that take the whole day and the whole week into account – not the ban alone.

What schools and parents can really do

From the body of research and the recommendations of klicksafe (the EU initiative for greater media literacy) and the BZgA, concrete and effective levers can be derived:

For parents

Clear, jointly agreed rules instead of constant arguments. As a guide, klicksafe recommends a maximum of one to two hours of free screen time per day for 12- to 16-year-olds, ending by 9 p.m. at the latest – more important than the exact number of minutes is a balanced daily routine with time for school, sleep and hobbies.
Use the free media use agreement (Mediennutzungsvertrag) from klicksafe and Internet-ABC – it explicitly includes rules for parents as role models too.
Phone-free zones and times at home: no device at the dinner table, no smartphone in the bedroom overnight.

For schools

Create a consistent, low-friction learning environment. What matters is not the ban on paper, but its reliable, low-conflict implementation in everyday life – without teachers having to act as the “phone police” every day.
Teach media literacy instead of only banning. The two belong together: a protected, distraction-free learning space and the ability to handle media in a healthy way.
Address warning signs early and connect with school social work and counselling services.

Conclusion

“Smartphone addiction” in the strict sense is rare – problematic media use, by contrast, is widespread and on the rise. Effective responses do not rely on a single lever, but combine clear rules, a distraction-free learning environment and genuine media literacy.

For everyday school life this means: a phone-free school delivers its impact when it is implemented consistently and without daily friction. That is exactly what we developed LOCKSTA for – read more about how over 50,000 lockable phone pouches at more than 200 schools and businesses ease everyday school life on our page for schools. We have summarised the current research for you in our research overview.

Frequently asked questions

From how many hours does it count as smartphone addiction?

There is no fixed hourly threshold. What matters is loss of control, the crowding out of other areas of life, and continued use despite negative consequences – not the sheer duration of use.

How many teenagers are affected?

According to the DAK/UKE study 2025, 6.6% of 10- to 17-year-olds use social media in an addictive way (around 350,000), and a further 21.5% in a risky way.

Does a phone ban at school help against smartphone addiction?

A ban alone mainly reduces use during school hours. Only holistic approaches – combining clear rules, a distraction-free learning environment and media literacy – work against problematic total use.