Dr Przybylski, the public debate is usually focused on the idea that our increasing use of screens is somehow detrimental to our mental well-being — where does this belief come from? And why is this matter still so divisive?

In every generation there is a collective anxiety about new forms of media, entertainment, or new ways that young people are spending their time. This can be traced back to the introduction of television, films, the printing press, even jousting of which some thought that it would encourage young people to war. If you want to go all the way back, you can even point to Plato who was afraid that oral culture would get lost through writing.

There are many things that are new in our environments and it is very rational to be sceptical of these. As you become older, every change in your environment appears more alien. On a very basic level being sceptic about something that is new is very important for survival. Digital screen time is the new kid on the block, when it comes to how we feel afraid of changes to our surroundings.

The other aspect is that a lot of technologies advance very quickly and this feels like a challenge to many. It is not just screens, but screens and the Internet, screens and games, screens and new forms of media, and so on, that people are worried about.

These two overarching trends culminate, along with a very seductive aspect. In many peoples’ minds, the other things we are afraid of for protecting young people do not have an off-switch. With screens the situation is different. While you cannot turn off child predators as a source of threat, you can actually turn off a phone or a PC. As a consequence, people are drawn to the illusion of control. The idea is that you can actually take a screen out of the child’s hands as opposed to all the other bumps in the night.

Do you think this is a meaningful debate that we are having right now?

To be honest, it would be quite silly for many people to have a serious conversation about something like paper time, so the time spent reading. For some reason, we don’t apply the same logic when it comes to screens. It is certainly not a meaningless discussion, but whether it is a useful one is an entirely different question. As a unitary concept screen time is a very strange thing to be talking about, but people care a lot about it.

Moving on to your study itself: As far as I understood it one of the main goals was to shed light on the prejudice that too much screen time is harmful — how did you study this and what did you find?

The objective was twofold. The first objective was to find out how much is too much, and in a second step how potentially bad too much could be for you. In statistical terms we wanted to determine the point where moderate turns into unhealthy and then to estimate how unhealthy unhealthy would actually be.

In order to study this, we partnered with scientists who carried out a health data collection of 120 000 English adolescents, all of them 15 years old. We added our questions to that data collection. Our aim was to specify exactly how we were going to analyse the data before the data came actually back to us. When you have very large datasets and an area where there is loads of concern with people either thinking there is no effect or a significant effect of something, scientists can often trick themselves into finding an answer that confirms their — or societies — existing biases.

If you read the literature on screen time you will find that different researchers have arbitrary cut-offs for what is a healthy amount of screen time and what isn’t. They will present statistically significant effects. As an outsider who does not have access to the data or to what they thought about the data before it is very difficult to know if this was always the way they had planned on analysing the data or whether it was adjusted to make it publishable.

You make mistakes as a scientist and may ignore or neglect certain variables that actually make the difference between significant and non-significant results. With this study is that we let the data fall where it may. It was entirely possible that the effects would have been larger, smaller or not existing at all.