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Wait, stop scrolling! How long have you been on your phone today? Is social media rotting your brain? We are constantly asking questions like these, but just how worried should you be about your screen time?

There are literally hundreds of thousands of studies looking at screen time, and many of them have found links between using screens and a huge variety of health issues, including depression, anxiety, poor sleep, obesity, diabetes and even suicide. It all sounds pretty bad.

There’s just one question: are screens themselves causing these issues, or is poor health causing increased screen time? Or could there even be an unknown, third factor influencing both?

The vast majority of these studies can’t tell you, because they merely show a correlation between screen time and health. Identifying causation – the real impact screen time is having – is much harder.

To get to the bottom of this, researchers conduct meta-analyses that pull together hundreds of high-quality studies using more advanced statistical techniques. Doing this, a lot of the harm seems to disappear.

My favourite such meta-analysis – yes, of course I have a favourite meta-analysis – was conducted in 2019. The researchers, Amy Orben and Andrew Przybylski, both then at the University of Oxford, looked at a huge dataset of questionnaires given to teenagers, allowing them to compare the effects of more than 20,000 different factors on the participants’ mental health.

Crunching the numbers, they found that only 0.4 per cent of adolescent well-being was related to screen use, a level of negative effect comparable to eating potatoes. By comparison, being bullied was associated with more than four times this negative effect, while getting enough sleep and eating a good breakfast were associated with much larger positive effects.

“ What the data seems to be telling us is that on average – on a population level – the positive and negative effects of screens are small “

So, screen time is fine? Well, again, let’s not be so hasty. Despite putting the links between screen time and mental health in context with other factors, these are still only correlations. People’s lives are messy, and extracting causation from messy data is hard.

One way to unpick the noise might be to ask what we actually mean by screen time. Watching TV, scrolling through social media on your phone, playing video games, reading an e-book or listening to a science journalist talk about screen time all involve staring at a screen, but would we expect them all to have the same impact on our health?

Many studies don’t take a particularly sophisticated approach to this question, simply counting up the number of hours spent looking at a screen – and to make matters worse, this data is often self-reported, which we know makes it less likely to be accurate. (Come on, we all lie about it.)