Is a lack of shut-eye the reason why your class is performing poorly? Gregory Stores introduces the first of a two-part series on sleep
Why has the standard of that teenage girl's work dropped? And why is that little boy always so hyper?
Your instinct may be that teenage hormones are to blame and the boy may have ADHD. But it's possible that both are seriously short of sleep.
Sleep is a neglected subject, in public health education and the training of professionals, including medics, psychologists - and teachers. So sleep disorders are at particular risk of being misconstrued.
When teachers are confronted by poor or erratic academic performance or troublesome behaviour, they should consider whether lack of sleep is the culprit. There is compelling evidence that many young people, especially adolescents, do not get enough.
American surveys have shown that only about 20 per cent of adolescents get the recommended nine hours on school nights and nearly half sleep for less than eight. At least once a week, more than a quarter fall asleep in school; and those who get insufficient sleep are likely to get lower grades.
Sleep is a complicated state of affairs. It is closely linked with many bodily processes and serves a variety of basic functions. It is connected with temperature control, reaction to stress, physical growth, resistance to infection and various metabolic and endocrine systems. Most obviously, it is necessary for restoration and recovery of the brain systems governing behaviour and cognitive function.
Sleep is biologically complex in other ways. It is not simply the shutdown of daytime activities. Complicated neurochemical processes are involved in going to sleep and waking up, and in switching several times during the night between non-rapid eye movement or NREM sleep, and REM or "dreaming" sleep.
The timing of sleep is controlled by a biological body clock in the depths of the brain, which is also involved in varying the level of alertness within each 24-hour period. You are usually most alert in the evening, which is the best time to study. Some people are more alert in the first part of the day and fade later ("larks"), while others are slow to get going in the morning and then are at their best late into the evening ("owls"). Most people fall between the two.
Of particular importance is the fact that the amount of sleep needed to function well during the day changes a great deal during childhood and adolescence. On average, newborn full-term babies sleep for about 16 hours in each 24-hour period; there is then a gradual reduction to at least nine hours in adolescence. From early adulthood onwards, most people need seven to eight hours' sleep.
There are some exceptions. The acid test is whether someone is feeling and functioning well during the day. Even those whose amount of sleep seems ideal may function even better if they are able to take an additional hour.
The likely effects of persistently poor sleep include feeling worn out, irritable or depressed, unable to concentrate and remember things properly, or make decisions efficiently.
Schoolwork requiring sustained concentration, creative thinking and abstract thought is likely to be particularly affected.
Whereas sleep-deprived adults tend to be slowed down, children may behave in the opposite way. The problem behaviour of some very active, impulsive children who cannot concentrate for long, said to have attention deficit hyperactivity disorder (ADHD), may, in fact, be the result of insufficient sleep.
It is important to identify such children because their treatment needs to be directed towards their sleep disorder. The stimulant drugs often used for ADHD are unlikely to be effective and may well make a bad situation worse by disturbing their sleep still further.
- Gregory Stores is Emeritus Professor of Developmental Neuropsychiatry at the University of Oxford.
Next week: how to spot and treat sleep disorders.
Stores, G. (2007). Clinical diagnosis and misdiagnosis of sleep disorders. Journal of Neurology, Neurosurgery and Psychiatry 78 1293-1297.
Stores, G (2001). A Clinical Guide to Sleep Disorders in Children and Adolescents. Cambridge University Press.
National Sleep Foundation. (2006) Sleep in America poll. www.sleepfoundation.org
Wolfson, AR, Carskadon MA (2003). Understanding adolescents' sleep patterns and school performance: a critical appraisal. Sleep Medicine Reviews 7 491-506.