Children aged eight to 11 who used screens for fun for less than two hours a day performed better in tests of mental ability, a study found.

Combining this with nine to 11 hours of sleep a night was found to be best for performance.

Researchers said more work was now needed to better understand the effects of different types of screen use.

However, they acknowledge that their observational study shows only an association between screen time and cognition and cannot prove a causal link.

And it did not look at how children were using their screen time, be it to watch television, play videogames or use social media.