Sleep specialists are urging high schools to delay start times to give teenagers more time to sleep.

Experts say teenagers that struggle to get out of bed are not lazy, but rather are just experiencing a fundamental shift in their body clocks.

"Teenagers get bad press when it comes to less sleep," associate professor Steven Lockley has told 7.30.

"Their parents forget what it was like when they were a teenager and want them to get up earlier and be active earlier."

The so-called circadian rhythms of teenagers mean they go to sleep later and wake up later, says Professor Lockley, a scientist from Harvard University in the US who is a consultant to Melbourne's Monash University.

As adolescents progress through their teens and into their early twenties, they require more and more slumber, he said.

A number of scientists are working to help teens get healthy sleep. One approach involves looking at how they can get teens to sleep earlier.

A new National Health and Medical Research Institute study being conducted by Monash University, Sydney's Woolcock Institute and Adelaide's Flinders University is examining the role of melatonin in what is known as delayed sleep phase disorder.

Dr Tracey Sletten, a sleep scientist at Monash, says Delayed Sleep Phase Disorder affects more adolescents than other parts of the population – striking 16 per cent of teenagers, compared with only three per cent of middle-aged people.

"We're testing through saliva samples the timing of somebody's circadian rhythm and we're looking at giving them a synthetic version of melatonin and actually helping them to advance their body clock and therefore go to sleep easier at night," she said.

Blue light from tablets, laptops affects body clocks

Professor Lockley says a more straightforward way of treating Delayed Sleep Phase Disorder is to avoid exposure to blue lights from technology such as tablets at night before teenagers go to bed.

"We are particularly concerned about devices that pump out a lot of blue light – because research has shown that blue light in the visual spectrum is best able to shift the clock," he said.

Scientists say looking at computers before bed can negatively affect sleep. ( Flickr: escapedtowisconsin )

"If you're using a blue light source like an iPad or laptop in the evening, this may shift your clock later.

"What we would ask everyone to do, including teenagers, is to avoid using those types of devices before bed and in the late evening and having more exposure to a red or a warmer colour in the evening."

Erika Struck, a mother of three from Blackburn in Melbourne's east, struggles to separate her son James from his smartphone when he goes to bed.

She has noticed a big difference in James this year, since he started high school and has to get up much earlier.

"He's generally a lot more tired," she said.

"He's dragging his feet a lot more, especially in the mornings and towards the end of the school week – things are a lot slower, his pace is a lot slower."

Sleep scientists are also pushing for high school to start later so teenagers do not lose valuable sleep and impair their brain function and learning.

"The biological clocks of teenagers push their rhythms later. So, asking a 15-year-old to wake up at 7am would be like asking me to wake up at 4am," Professor Lockley said.

Changing school start times one solution

He says research in the US and Britain demonstrates more sleep profoundly affects educational outcomes.

"Pushing school start times later, which has happened in a number of cases, has been shown to benefit the educational attainment of the children, but also behavioural outcomes – things like truancy," he said.

"We even think there are some improved risks of some more serious disorders such as mental health problems, depression and even suicide risk in teenagers along with more sleep and better bedtimes.

"This is a serious matter; it's not just about lazy teenagers falling asleep."

Changing start times can also be more effective than small class sizes.

"There was an economic study in the US which compared the cost of reducing class sizes with the costs of shifting school start times later," he said.

"The economists stated that you could get the same educational benefits with a later school start time – for about one-seventh of the cost of changing class sizes."

Ms Struck says later school start times sound nice in theory but they would be a nightmare for busy working parents.

But Professor Lockley says practicality should be secondary to educating children.

"I'm sure there are ways to work that out within families or across society – more flexible work times for parents would be helpful," he said.

"But if we really want to increase the education of children simply and relatively inexpensively, these are problems we should be able to solve."

If you would like to be part of the Delayed Sleep Phase Disorder study, go to www.monash.edu.au/sleepstudy