More than half of all teenagers may be sleep deprived, according to experts. A combination of natural hormone changes and greater use of screen-based technology means many are not getting enough sleep. Research has suggested teenagers need nine hours' sleep to function properly. "Sleep is fundamentally important but despite this it's been largely ignored as part of our biology," said Russell Foster, Professor of Circadian Neuroscience at Oxford University. "Within the context of teenagers, here we have a classic example where sleep could enhance enormously the quality of life and, indeed, the educational performance of our young people. "Yet they're given no instruction about the importance of sleep and sleep is a victim to the many other demands that are being made of them." 'All-nighters' At One Level Up, an internet cafe and gaming centre in Glasgow, I found a group of young people who are used to very late nights. "There's things called 'grinds' which we have on Saturdays which are an all-nighter until 10 in the morning," said 17-year-old Jack Barclay. "We go home, sleep till 8pm at night and then do the exact same thing again. I like staying up." Fourteen-year-old Rachel admitted occasionally falling asleep in class because she stayed up late at night playing computer games. "If it's a game that will save easily I'll go to bed when my mum says, 'OK you should probably get some rest', but if it's a game where you have to go to a certain point to save I'll be like, 'five more minutes!' and then an hour later 'five more minutes!', and it does mess up your sleeping pattern. "For me it takes me about an hour to get to sleep and I'm lying there staring into nothing thinking 'I'm going to play THAT part of the game tomorrow and I'm going to play THAT part of the game the next day." Hormonal changes Research has shown that teenagers naturally veer towards later bedtimes and are later to rise in the morning, possibly because of the hormonal changes that occur during puberty. However Prof Foster said electronic equipment accentuated this natural night-owl behaviour. He explained: "The data that's emerging suggests that these computer screens and gaming devices may well have a big effect in increasing levels of alertness. "That will make it harder to get to sleep after you've stopped playing. "The great problem with teenagers is that you're not only biologically programmed to go to bed late and get up late, but there's also many attractions like gaming and Facebook and texting and many teenagers are doing this into the early hours of the morning and delaying sleep even further." Psychologist Jane Ansell set up the charity Sleep Scotland to help children with special needs establish good sleeping patterns. However an increasing amount of the charity's workload is now spent working in mainstream schools with teenagers. "People were being sent to me and were generally being diagnosed with Aspergers, and a lot were being diagnosed as ADHD," she said. "I felt the first thing we had to do was to work out a sleep programme for them so that they weren't sleep deprived. Once they weren't sleep deprived, some no longer had ADHD symptoms because the symptoms of hyperactivity and sleep deprivation are pretty similar. "I'm not saying they were all free of ADHD but it is a common mistake." Pilot studies Her pilot studies in three Scottish schools suggested 52% of teenagers were sleep deprived, and about 20% reported falling asleep in class at least once in the last two weeks. While many teenagers have received exam grades over the summer, Ms Ansell said most of them did not realise that a healthy sleeping pattern could have improved their performance. She added: "We have probably not understood how important sleep is. "It affects your growth, and especially things like memory consolidation. "If you don't have enough sleep your short term memory doesn't consolidate into your long term memory which is going to affect your school grades."