If Elise Hill is asleep by 10pm, that counts as a success. Her parents have got used to the two-year-old going to bed at 10.30pm, after three and a half hours of trying to get her to sleep. Elise will insist it can’t be bedtime, not yet. She’ll run away, hide, ask to watch TV. She’ll grab the iPad and start playing a game. Some nights, it takes a half-hour battle just to get her pyjamas on.

A bright girl with caramel-coloured hair and an irresistible smile, it’s easy to see how Elise might have taken control of her bedtime. But in the mornings she doesn’t want to get out of bed. Her mother, Jayne, leaves her to sleep as long as she can, before finally getting her up at 8.15am. Elise is then rushed out of the house so Jayne can get her to nursery before she’s late for work.

At their home in South Yorkshire, Jayne and Nick, Elise’s father, are shattered. “I’ve sat in the car park at work, crying,” Jayne says. “You think about it 24/7. You dread bedtime. It just consumes your whole life. One word: sleep.” There is no time left for them as a couple. “We come downstairs, he feeds the cat, I make a cup of tea, we sit on the settee, watch 15 minutes of telly, and then I fall asleep. You feel like you’re a bad parent. Useless, absolutely low and on the verge of depressed.”

Across the world, children are sleeping less. It’s not just young children like Elise who can’t switch off: from toddlers to teens, bedtimes are getting later and average sleep duration is falling. (Everyone’s needs are different, but health professionals recommend that five-year-olds should get around 11 hours a night, 10-year-olds around 10 hours, and 15-year-olds nine hours). The NHS is seeing more serious problems than ever: hospital attendances for children under 14 with sleep disorders have tripled over the past 10 years. Specialist paediatric services are overwhelmed: Sheffield children’s hospital has seen a tenfold increase in referrals over the last decade. A 2011 study based on schoolteachers’ observations found that English students are the most sleep-deprived in Europe.

There are a number of reasons for this, chief among them our increasing dependence on technology, a more child-centred style of parenting, poor diet and the example set by an older generation, who work longer hours, come home later, and constantly check their phones. Addressing the issue won’t just benefit children’s health, the specialists argue: it will save money. At a time when NHS services are extremely stretched, and adolescent mental health services face a funding crisis, Britain’s sleep problem is costing unnecessary millions in prescriptions, GP appointments and specialist care.

Fortunately for Jayne and Nick Hill, there is help available – but only because they happen to live in the right postcode. NHS Doncaster has funded the Children’s Sleep Charity to provide a clinic, the only free specialist service in the country that supports families of children of all ages, regardless of whether they have a disability. Parents can refer themselves and get an appointment within weeks; it can take four months to get a referral to a paediatrician. The charity runs clinics several times a month in locations around Doncaster.

Founder Vicki Dawson survived five years as a sleep-deprived mother. “When you become a parent, you expect a certain level of sleep deprivation – babies don’t sleep. But when that continues over a number of years, it really starts to take its toll. I experienced memory loss, it was hard to concentrate at work, even driving was difficult and dangerous. I asked for help from my GP, and nobody was able to offer me any advice other than to recommend books. When you’re sleep-deprived and you’re working, the last thing you’re capable of is reading a book.”

A former deputy headteacher, Dawson last year gave up her day job to run the charity full‑time. She gets up to 200 emails a day. “We can’t meet the demand. We have parents telephoning from across the UK, and that feels like a huge responsibility because there’s nowhere else.” The charity can fund one-to-one support for local families; everyone else has to read its leaflets online.

***

The waiting area at Wheatley children’s centre is filled with mothers with grey faces and hollow eyes. Many of them have spent vast amounts of time and money trying to get their children to sleep. They have tried books, online parents’ forums, white noise, scented oils, vibrating teddies, light shows that project on to the bedroom ceiling. Some have put furniture up for sale to try to meet the cost of private help.

Jayne Hill has an appointment with sleep practitioner Claire Earley, who asks her about Elise’s nightly routine. She explains that Elise has never been a child to go to sleep at seven, but they are aiming for her to be in bed by 8.30pm. Their work schedules mean the family doesn’t have dinner at the same time every day. Elise stays up so they can all sit at the table together. Then she plays on the iPad.

“Is the TV on at this point?” Earley asks.

Jayne says yes.

“What time would you say that was?”

“Probably about 8.30pm.”

“Any screen will keep her awake,” Earley says. “We do ask that parents switch it all off an hour before bedtime to give the brain time to relax.”

It’s well established that technology tells our brains not to go to bed. The blue light emitted from tablets, smartphones, computers and LED TVs interferes with the production of melatonin, the hormone naturally released as the sun goes down that makes us feel sleepy. The blue light filters now available on many devices address only part of the problem: TV on demand, addictive games and fear of missing out on social media make it harder than ever to switch off. Even when we do, our brains are still in overdrive; technology that didn’t exist 10 years ago has taken over our children’s lives in completely unforeseen ways.

This is all news to Jayne. Elise was quiet with the iPad and TV, she says: “I thought it was calming her down.” She has come to rely on that time to do the housework – a rare moment to herself. “I wouldn’t have thought that just having the television on, even if she wasn’t looking at it, would affect her sleep. That’s the first thing I do when I come in: put the telly on.”

Earley gives Jayne a plan: all screens must be off by 7.30pm, then Elise should play with her train set or Play-Doh: games that require hand-eye coordination and help the brain wind down. Then a bath, and bed at 8.30pm.

“If she was to make any attempt to get up, you would say, ‘It’s sleep time’, lay her down and come back out again. No other conversation, no eye contact. You’re responding to her, but you’re not engaging with her. You may have to do it 20 times, you may have to do it 40 times. It will be a case of who’s going to give in first.” Jayne and Nick hate the idea of Elise falling asleep distressed, but this has been going on for too long. Earley says she will follow up over a number of weeks to see how the new routine is working.

From two-year-olds to 14-year-olds, every case Earley and her fellow sleep adviser Carol Batchelor advise on that day involves a child who uses a smartphone or tablet before bedtime. According to a recent survey by consultancy Censuswide, over 80% of children in the UK now have their own phone by the age of 12. By 10, 58% have their own tablet, and two-thirds of teenagers say they use these devices in the hour before bedtime.

“The look of horror on a teenager’s face when you say, ‘You really shouldn’t have your technology right before bed.’ They think they need it,” Batchelor tells me. “It’s like asking them to remove their right arm,” Earley says.

“Many children will have forgotten that they like reading and they like Lego,” Batchelor adds.

The families coming to see them often want a panacea or pill that will make their child’s problem vanish immediately. The behavioural approach they recommend instead takes time, but is very effective: 92% of the 167 families who used the clinic over the past year reported that their child’s sleep issues were successfully resolved within six months. And in the cases where they can’t help, the charity refers families to Sheffield children’s hospital for overnight observation.

Dr Heather Elphick, who leads the service in Sheffield, is one of a handful of paediatric sleep specialists in the country. She says that most GPs tend to reach for the prescription pad. “They don’t have any other options. If every general practice had a sleep practitioner they could refer a child to, in most cases they would avoid the need for medication.” Synthetic melatonin in tablet form is commonly prescribed to children with sleep issues. It is unlicensed for use by anyone under 55, but GPs can prescribe it at their own discretion; the number of unlicensed NHS prescriptions has increased tenfold in a decade.

Ten-year-old Harley Walker has had poor sleep all his life, and no one has been able to explain why. After doing the rounds of appointments with GPs and paediatricians, he is spending the night in Sheffield’s sleep lab with a Medusa’s head of brightly coloured wires glued to his skull. His mum, Abigail, will sleep in a camp bed next to him.

Harley has trouble falling asleep and staying asleep, and then wakes up too early. His younger sister and brother sleep very well, and his parents have tried to ignore him when he wakes in the middle of the night, to encourage him to go back to bed. But that means Harley sometimes wakes his siblings up on purpose, knowing that his parents will have to get up to settle them all.

“He gets up at four or five o’clock, ready for that day, school uniform and everything,” Abigail smiles, wearily. But Harley doesn’t relish school. “I don’t get on with people very well,” he tells me, matter-of-factly. “I get moody and stroppy, and then I get told off.”

Six months ago, their GP suggested that Harley might have attention deficit hyperactivity disorder (ADHD), and the family are awaiting the results of an assessment. In the meantime, he has been taking synthetic melatonin since November. “It made a difference to start with,” Abigail says, “but now he’s back to how he was.” At only 10, Harley is potentially looking at a lifetime on sleeping tablets. “I’d prefer [the solution] to be something different,” his mother says, “rather than taking medication for the rest of his life. I’m willing to try anything.”

In the lab, the nurses wait the three hours it takes for Harley to fall asleep before they can assess his brain waves, respiration and physical movements, gathering data that will be passed on to sleep physiologists. The results will take several weeks, and there is every chance that his problems will remain unexplained. Until they have an alternative strategy, Harley will keep taking the pills.

Elphick suspects many children are being misdiagnosed with ADHD when they are simply not sleeping properly. “Sleep deprivation can lead to behaviours which mimic ADHD. In some cases we can intervene, improve their sleep and avoid that diagnosis,” she says. “Chronic sleep deprivation can also lead to mental illness – particularly in adolescents, where it can lead to depression.”

Poor sleep is a potential timebomb for a child’s physical health, too, compromising the immune system and creating a greater likelihood of picking up infections.

Catherine Hill, a consultant paediatrician at Southampton children’s hospital, argues that sleep is as vital to a child’s wellbeing as good nutrition – perhaps even more so – quoting robust research that shows sleep-deprived rats died more quickly than those that were starved. “If you could manufacture a pill that could improve your cognitive function, that improved your emotional regulation, that stopped you reaching for the biscuit tin in the afternoon, you’d be a millionaire. That is what sleep can help you with. It’s free, and available to us all,” she says. “How often will a parent say to a child, ‘If you’re good, you can stay up late’? When would you say to a child, ‘If you’re really good, you can go without supper tonight’? It’s absolutely equivalent.”

***

Perhaps the greatest long-term health risk to a child who doesn’t sleep is the danger of becoming obese. The mechanism by which sleep-deprived children are more likely to put on weight isn’t fully understood, but there are many strong hypotheses. As well as having less energy to exercise, and more opportunity to eat because they are awake for longer, it is thought that the body’s balance of leptin and ghrelin – the hormones that tell our brains we’re full or hungry – is abnormal in children who haven’t slept enough. Tired children are more likely to crave foods that are high in fat and sugar.

Every morning, 13-year-old Ellie Keady covers the bags under her eyes with thick makeup before heading off to school. She goes to bed at 9pm, but rarely gets to sleep before 2.30am. “Sometimes I’ll go to school and I’ll have had only two and a half hours’ sleep,” she says, with wide, weary eyes.

When we meet at her home in Sheffield, Ellie is wearing her workout gear of black leggings and a grey T-shirt. She is 14st 7lb – significantly down from her heaviest weight of 17st six months ago, but still obese. She has a personal trainer and is taking his strict diet and exercise programme seriously, having previously tried “every fad diet that you can do for a child”, according to her mother, Joanne.

The sleep problems began at the same time as Ellie started putting on weight. She broke her foot badly aged seven, and was in a wheelchair off and on for months. Once a keen gymnast who represented Sheffield, Ellie had to learn to stand, walk and run again. “The weight just came on,” Joanne tells me. “Her confidence had gone. Bullying started and everything went downhill. Ellie didn’t want to go out.” She has been sleep-deprived ever since.

Her schoolwork has suffered. “She’s had a lot of time off, and she gets viral infections over and over again. If you sneeze in her room, Ellie will catch the flu. It’s like having a newborn baby.” On so little sleep, Ellie had little emotional resilience when other children started picking on her. “She’d get really angry, and have a go back. She’d get excluded,” Joanne tells me.

“I’d be so tired I just couldn’t deal with it,” Ellie adds.

Life is getting better – she is at a new performing arts school that she loves – but her sleep problem is still a thick cloud hanging over her as she enters her teens. “When my friends are all going out, I know I can’t, because I’ll be too tired,” she tells me, quietly. “I feel left out, even though I’ve been invited.”

An overnight stay in the Sheffield children’s hospital lab showed no signs of Ellie having sleep apnoea. (This occurs when excess weight makes the airway collapse during sleep, causing sufferers to struggle to breathe; in the most serious cases, children have to sleep with a ventilator.) This was a relief for the family, but also the first time they had heard there was a link between sleep deprivation and weight gain. When the nurses explained the connection, it rang true for Ellie.

“Sometimes when I’ve had a terrible night’s sleep, I think, ‘Oh, do I have to do training today? Can I just have a McDonald’s?’ I never knew that was from being tired. I thought that was from being lazy.”

With apnoea ruled out, the Keadys still don’t have an explanation for Ellie’s sleep problem. Her bedroom holds a few clues, though. Just big enough to fit a single bed, a cupboard and a chest of drawers, it is filled with devices: a television opposite the headboard, alongside Ellie’s phone and two iPads. It may take changes in her evening routine, as much as a strong commitment to losing weight, for her to see any improvement.

***

Today’s teenagers have grown up in a tech-obsessed, sleep-deprived culture, and have now hit an age when they are under pressure to perform academically. Sleep physiologist Dr Guy Meadows regularly goes into secondary schools to run workshops for teenagers, many of whom have no idea how much bad sleep is impairing their ability to learn.

“Some research showed that if children are sleep-deprived by just an hour a night, it could reduce their cognitive academic performance by up to two whole years,” he says. Meadows is calling for sleep to be a compulsory part of personal, social, health and economic (PSHE) education. “We need to recognise that sleep is one of the most powerful performance-enhancers known to humankind. If you are serious about your child’s academic performance, then schools and parents should be really helping them get good quality sleep on a regular basis.”

This is because, when we are sleeping, our brains are very active. While in deep sleep, all the information children have learned gets selected, consolidated and stored in the long-term memory, so it can be put to good use at a later date. A child has to be awake enough to be focused and attentive in the first place, Meadows says, and then well-rested to recall those memories and use them to solve problems in future. Poor sleep can affect every stage of the learning process. “If you’re pulling an all-nighter and cramming for exams, you’re actually preventing your brain from laying down the information you’re learning,” he explains.

“Our benchmark of what’s normal is changing. For children and adults, waking up feeling tired is becoming the new normal. So people are just reaching for energy drinks, reaching for caffeine as ways of coping and seeing that as perfectly normal. Parents need to make their children aware of the importance of sleep, and perhaps become role models for their children, showing them, ‘I don’t stay up late, I have a regular bedtime, I don’t stay on my smartphone before bed.’”

It is also possible that many parents don’t recognise their child isn’t sleeping enough: most of the teenagers who participated in a recent survey for the Children’s Sleep Charity said they had problems falling asleep and difficulty getting up; but 80% of their parents said they didn’t think their child had an issue at all.

For the NHS, there are big savings to be made. Lee Golze, the NHS Doncaster manager who agreed to fund the local clinics, says it’s one of the most cost-effective things he has ever commissioned. “A direct, face-to-face intervention, with a five-week follow-up, is £80,” he says. Compare that to the cost of prescribing a child synthetic melatonin for a year: “An average dosage, maybe an appointment with a clinic and a follow-up with a consultant, would be about £1,000.”

Dawson claims the savings to the public purse go even further. “Children are taking up paediatrician and GP appointments that are not appropriate for them. We had one child recently where we improved his sleep and the school was able to withdraw the number of teaching assistants they had – again, a cost-saving benefit. We’ve had families who have split up, parents who’ve not been able to work: it has cost society in benefits.” But, for the moment, these savings are just for Doncaster.

“We desperately need to get children’s sleep on to the public health agenda,” says Catherine Hill. “We’ve done it with nutrition – people understand the dangers of sugar and obesity. We now need to wake up to the importance of sleep.”

***

Last week, Sheffield children’s hospital came back with the results of Harley Walker’s overnight stay – and found no medical explanation for his poor sleep. They will review his routine, and his medication. The whole family remains desperate for a night of peace; his mother has asked the GP to double his melatonin.

Meanwhile, after only a few days of following the plan recommended by the sleep clinic, Elise Hill is going to sleep an hour and a quarter earlier. Jayne and Nick look as if they have had a holiday. “It feels a little bit surreal,” he grins.

Jayne agrees: “The main difference we’ve made is to turn the television off and not give her the tablet. I haven’t been running around trying to cram everything in, and we’ve solely focused on the bedtime routine. She’s been so much happier in the morning – you can just see it in her face when she wakes up.”

“I feel a little bit embarrassed and a little bit guilty, actually,” Nick adds, “because we thought we were doing everything right. You get so much advice about diet and food. Five a day, seven a day, whatever. But you don’t get any advice about sleep.”

Sleep tight: tips for a good night

1 Avoid sugary snacks and caffeine, particularly at supper time. Opt for alternatives like banana, porridge or wholemeal bread.

2 Think about the bedroom environment: is it calm and conducive to sleep?

3 Have a consistent routine that you follow every evening in the hour before bedtime.

4 Consider whether bathtime is relaxing. If it isn’t, separate it from the bedtime routine. If it is, have the bath 30 minutes before bedtime to allow the body temperature to rise and then drop again – this helps us feel sleepy.

5 No screen activity in the hour before bed; no TVs, computers, phones or tablets.

6 Activities involving hand-eye coordination help the brain wind down before bed, eg jigsaws or colouring in.

7 Have a set wake-up time, even at the weekend.

8 Provide your child with a visual cue so they know when it’s time to get up, like a light on a timer. That way they know it’s time to sleep when the light is off.

• Source: the Children’s Sleep Charity.

Jenny Kleeman’s film for Panorama, Sleepless Britain, will be broadcast on 6 March at 8.30pm on BBC1.