Researchers at King’s College London and Cardiff University have looked at 11 studies and discovered that smartphones and tablets in bedrooms disrupt the sleep of children even if they are switched off.

They found that using smartphones or tablets before bedtime doubled the risk of a disrupted night’s sleep and doubled the chances of feeling excessively sleepy the following day. Sleep was also significantly disturbed by the mere presence of devices – almost to the same level as actually using it. This suggests that if you want your precious snowflake to sleep you should remove them from the bedroom. In the case of the iPhone you should also hit it with a hammer several times – the iPhone not the kid.

Apparently the issue is that the ‘always on’ nature of social media and instant messaging means children are continuously stimulated by devices in their environment, even when they are not using them.

Dr Ben Carter, of King’s College London, said: “Our study provides further proof of the detrimental effect of media devices on both sleep duration and quality.

“Sleep is an often undervalued but important part of children’s development, with a regular lack of sleep causing a variety of health problems. With the ever growing popularity of portable media devices and their use in schools as a replacement for textbooks, the problem of poor sleep amongst children is likely to get worse.”