A new study has suggested the effect of blue light from smartphones on sleep may not be as great as previously thought.

Smartphone and tablet screens emit blue light to our eyes which keeps us awake.

A new report in the medical journal Sleep Medicine Reviews has questioned this conclusion.

Clinical psychologist and co-author Michael Gradisar suggests screens are overrated.

"There's no evidence from 11 studies conducted across the world that screen light in the hour before bed makes it harder to fall asleep," he said.

Sleep expert Tom Coleman told Lunchtime Live the study is suggesting blue light is just as bad as others.

"This research has come out from the University of Basel and it is a little bit flimsy - I would say maybe it's a little bit misleading," he said.

"What it's saying is different light frequencies have the same impact on sleep.

"It's not that blue light is more damaging to sleep."

A couple ignoring each other lying in bed at night while using mobile phones. Picture by: Tero Vesalainen / Alamy

Mr Coleman said both white and blue has been shown to lower melatonin secretion which helps bring on sleep.

"It's what you're doing on your phone and how long you're spending on it," he said.

"This is something I've always said: I'm not so much worried about the light, I'm worried about the addictive quality of the phone.

"It will disrupt and rob you of sleep".

Mr Coleman said different people can be affected in different ways.

"We've different genes that influence our sleep and some research has shown that some people are more sensitive than others," he said.

"So genetics do some into it but it's the alerting behaviour - that's the disruptor.

"It's so hard to get off these social media apps; they're highly addictive and they've been designed that way".

'Digitally obsessed'

Mr Coleman said these apps are not making us happier.

"We're not getting any happier, global depression rates are on the up," he said.

"We're living now in this kind of digitally obsessed world.

"Many people do reach for the phone and they can't get off them - that's my worry".

Mr Coleman added that a major US study in teenagers found "lower mental wellbeing, lower curiosity, lower self control."

He added that the issue with blue light should be parked and we should examine "what we're doing on our phones and why."

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Main image: Woman looking at smartphone at night in bed. Image: Tero Vesalainen / Alamy