If screen time is not the decisive factor, why control it at all, and how do tools like TikTok's time limit or the one sec app work?

Time alone does not decide mental health or addiction, but monitoring and reflecting on it builds awareness. TikTok's built-in limit is a weak nudge (the code to continue is printed on the screen), whereas one sec uses self-nudging: it delays opening an app, which measurably reduces use.

The principle: screen time is not the main factor for mental health or for developing an addiction. Still, it is worth controlling and reflecting on it, via the phone's own settings or inside the app, because the number makes an otherwise invisible habit visible.

TikTok sets a daily screen-time limit of one hour for young users. When it runs out, the app asks "Do you want to close TikTok?" but lets you continue by typing a code, and the code (e.g. 1234) is shown right there. The platform can say it protects well-being while the barrier costs one second.

one sec works by self-nudging: the user chooses which apps to slow down; when they open one, a short pause (e.g. a breath) appears before the app loads, with the option to close it. The friction turns an automatic tap into a conscious decision. The maker reports that use of the targeted apps falls by 57%; the peer-reviewed study with the Max Planck Institute and Heidelberg University (PNAS 2023) found that users gave up about one in three opening attempts and tried to open the apps 37% less often after six weeks.

For help beyond self-control: self-tests and SafeZone, an anonymous online addiction counselling service.

Go deeper:

• Grüning, Riedel & Lorenz-Spreen (2023): Directing smartphone use through the self-nudge app one sec (PNAS) — the field study behind the app's claims.
• Wikipedia: Nudge theory — how small changes in choice design steer behaviour.
• SafeZone.ch — anonymous online counselling on addiction (German).