Are Children Getting Enough Sleep? Implications for Parents
by Luci Wiggs
Oxford Brookes University
Sociological Research Online 12(5)13
<http://www.socresonline.org.uk/12/5/13.html>
doi:10.5153/sro.1557
Received: 8 Jan 2007 Accepted: 21 May 2007 Published: 30 Sep 2007
Abstract
Sleeping is a child's primary activity; by the time an average child goes to school they will have spent more time sleeping than engaging in any other activity, such as playing, eating or interacting socially. Disturbances of sleep (especially sleeplessness) are one of the most frequent child behaviour problems to be reported by parents, affecting about 30% of typically developing children and adolescents. The definition of 'sleeplessness problems' will be considered noting how, with child sleeplessness, the complainant and the sufferer are frequently not the same person (frequently parents are the former and the children the latter), and that this has implications for how we should define and, where appropriate, attempt to 'treat' these problems. Parental perceptions and parental sleep patterns, moreover, may be key in understanding how some child sleeplessness problems are conceptualised, how they might impact on the child and family and the mechanisms by which successful intervention for childhood sleeplessness may result in benefits for families. The author suggests that child sleeplessness might be better theoretically conceptualised as comprising two distinct states with different causes and effects. Firstly, a `biologically-defined sleeplessness` characterised by a child having objectively impaired sleep quantity and/or quality, relative to their biological sleep needs. Secondly, a 'socially-defined sleeplessness' characterised by the child's sleep pattern deviating from a desired sleep pattern. Judgements about what constitutes a 'desired' sleep pattern will be influenced by multiple factors including expectations and culture. Both of these states may exist independently, or co-exist. Both of these states must be considered in order to decide whether or not children are getting enough sleep.
Keywords: Children Parents Mothers Fathers Sleeplessness -
Introduction
Even thus last night, and two nights more I lay, And could not win thee, Sleep, by any stealth: So do not let me wear to-night away. Without thee what is all the morning's wealth? Come, blessed barrier between day and day, Dear mother of fresh thoughts and joyous health!1.1 Scientific study supports Wordsworth's ideas about the physically and psychologically rejuvenating effects of sleep, and the distress associated with a lack of sleep. This quote is of particular interest because it refers to the problems associated with lack of sleep; many writers throughout history have described sleep as 'gentle', 'a balm', 'a bath' 'peaceful', even 'death-like' to suggest the warm, welcome, reduction of activity associated with sleep. Behaviourally, in humans, the state of sleep is a time of quiescence, a period when eyes are shut and we lie quietly in a state of reduced, but rapidly reversible awareness. Physiologically, in contrast, there is much activity, and the process of initiating and maintaining sleep is not simply a passive process arising as a result of a 'lack of wakefulness'. It is beyond the scope of this paper to provide a detailed account of normal sleep physiology (readers are referred to Kryger et al., (2005) and Sheldon et al.,(2005) for further information, including developmental aspects), but it needs to be emphasised that basic sleep/wake states have a biological basis. However, some aspects of sleep (e.g. sleep-related behaviours) may be far more influenced by social factors and other aspects of sleep (e.g. the timing of sleep) may be determined by an interaction of biological and social processes.~William Wordsworth, "To Sleep"
1.2 Sleep occupies about a third of our life in total but proportionately much more of a child's life; sleeping is a child's primary activity. By the time an average child has gone to school they will have spent more time sleeping than engaging in any other activity, including playing, exploring their world, interacting with others or any other of the important activities which constitute a child's life (Mindell & Owens, 2003). The large need to sleep suggests that sleep must serve some very fundamental purpose although the precise function of sleep remains elusive. The various theories advanced have emphasised physical and psychological restoration, energy conservation, consolidation of memories, discharge of emotions, brain growth, and other basic biological functions including the maintenance of immune systems (Sheldon, 2005). No one theory is adequate across all species and stages of development and sleep is likely to serve multiple purposes (Rechtschaffen,1998).
1.3 One way in which researchers have tried to determine the function of sleep is to experimentally examine the consequences of lack of sleep. A number of studies suggest that sleep disturbance is associated with a wide-range of serious compromising effects on cognition, mood and behaviour (Pilcher & Huffcutt, 1996; Fallone et al., 2002), although most experimental studies have been conducted with adult populations and whether the results can be extrapolated to children is open to question. Experimentally reduced or disrupted sleep in children has been shown to be associated with impaired memory, vigilance, reaction time creativity and increased sleepiness (Carskadon & Dement, 1981a; Randazzo et al., 1998; Fallone et al., 2001; Sadeh et al., 2002; Sadeh et al., 2003) although one study failed to find any effect of restricted sleep on children's subsequent functioning (Carskadon & Dement (1981b) with the effects only becoming apparent following total sleep deprivation (Carskadon & Dement 1981a). Some recent experimental work with typically developing children who were 'good-sleepers' suggested that the amount of sleep loss needed to induce impairments in neuropsychological functioning was quite subtle (i.e. a matter of about 30 minutes) and conversely, that extending normal sleep by a similar small amount could lead to improvements in performance on some tests of memory, reaction time and vigilance (Sadeh et al., 2003).
1.4 In addition to these 'direct' effects of sleep loss one must also consider the consequences of a child's disturbed sleep in a broader context. As Williams, Lowe and Griffiths (in this Special Issue) suggest, sleeping is a key part of childhood life and also parenting. When children's sleep is disturbed it is frequently the case that other family members (e.g. parents or siblings) also have their own sleep patterns, and aspects of their waking life, disturbed. The precise nature of a child's sleep disturbance will be highly significant for determining who is affected and in what ways.
1.5 For many children, and their families, the sleep period is not, contrary to literary suggestions, a time of peaceful restoration but rather a time of distress, conflict or wakefulness. This may be because the child suffers from one of the many primary sleep disorders which may compromise sleep quality or quantity (Stores, 1996). The term 'sleep disorders' encompasses a number of diverse conditions; there are over 80 different sleep disorders listed in the International Classification of Sleep Disorders (ICSD) (American Sleep Disorders Association, 2005). In broad terms these can be categorised as falling into three main problem areas: sleeplessness (e.g. difficulty getting to sleep or staying asleep) sleepiness (e.g. an increased need to sleep) or behaviours/episodes which are associated/intrude into sleep (e.g. nightmares). Children's sleep may be disturbed for reasons other than a primary sleep disorder. e.g. secondary to another medical or psychiatric condition (e.g. asthma or anxiety) or because of social/environmental demands, which make it difficult for children and adolescents to get the sleep that they need. In addition, importantly, in deciding whether or not a child's sleep is disturbed (in quantity or quality) by implication one must refer to an 'ideal' from which one considers the child's sleep pattern to deviate. The definition of an ideal sleep pattern may vary depending on the informant (e.g. the child themselves, the parent, a clinician) and any discrepancies in the expectations of informants, or a mismatch between parents' and children's sleep needs, would be salient. In trying to answer the question about whether children are getting enough sleep one must be careful to interpret the literature being mindful of the fact that different groups of people may use different criteria to answer this question.
1.6 It is lack of sleep, or sleeplessness (i.e. difficulty getting to sleep, problems staying asleep and waking too early in the morning), which appears to be the most common and intractable problem that clinicians and parents are faced with (Mindell & Owens, 2003), and this is also the type of childhood sleep problem to which most of the research literature is devoted. This paper will attempt to consider some of the issues surrounding our conceptualisation of sleeplessness (and adequate sleep) in children in adolescents.
Defining sleeplessness
2.1 Sleep needs to be assessed both in terms of its quantity and its quality. Adequate, good quality sleep is required to ensure that one's individual sleep needs are met and one does not suffer any of the well-established direct consequences of sleep deprivation, as highlighted by the experimental sleep deprivation studies described above. At a pragmatic level, deciding whether children are getting enough sleep is perhaps not best answered by referring to 'normal' values of sleep for children of different ages since there can be much individual variation in sleep need, but rather may be best answered by looking at children's level of daytime functioning. If a child is functioning optimally during the day they are probably getting enough sleep. But defining 'optimal functioning' is in itself perhaps even more problematic so attempts have been made to classify normal childhood sleep patterns.2.2 The ICSD (American Sleep Disorders Association, 2005) contains criteria for the diagnosis of various sleep disorders, including common causes of sleeplessness in children (e.g. behavioural insomnia of childhood, inadequate sleep hygiene etc). The criteria typically involve terms which require a judgement to be made (e.g. falling asleep is an extended process; sleep is significantly disrupted; sleep onset associations are highly problematic) and, as such, they are a clinical tool designed to take into account the personal, family and cultural variations which will exist in connection with judgements about child sleep.
2.3 Definitions of sleeplessness vary considerably across different published reports with only the minority using the ICSD criteria. Some authors have categorised children as 'good' or 'bad' sleepers on the basis of parent-report (or, less often, self-report) of sleep being a 'problem'. Such an approach has merit in detecting the subjective evaluation of sleep but, as already intimated, the variability of factors which may influence this judgement makes it difficult to compare groups of children or to identify which aspects of the child's sleep pattern might be particularly disruptive (Scher, 2002, Giganti & Toselli, 2002). Further, as the study by Sadeh et al., (2003) elegantly demonstrated, 'adequate sleep' cannot simply be defined in terms of an absence of reported difficulty with sleeplessness; in that study even children without reported sleeplessness problems performed better on some tests of neurobehavioural functioning following increased sleep.
2.4 Children's own definitions of 'problems with sleep' is an interesting area for future study. The definition of adult insomnia is a subjective complaint of inability to sleep or unrestorative sleep (American Psychiatric Association, 2000; American Sleep Disorders Association, 2005). This definition might also be appropriate for use with some children. However, for others, sleeplessness may only be a problem under certain conditions and not, for example, if wakefulness affords an opportunity to engage in a pleasurable activity (e.g. watching TV, socialising, reading etc.). As intimated by Williams et al., (in this Special Issue), for some children, going to bed, and to sleep, is a cessation of opportunity for pleasurable activities enjoyed during wakefulness and, further, remaining awake for longer may also be construed as a sign of maturity (i.e. adults stay awake later than children and thus staying up late is a positive sign of status). In such circumstances, sleeplessness might be construed positively. It might be hypothesised also that there is a developmental shift at some, as yet, undiscovered point where the recognition of the consequences of inadequate sleep (at the time and the next day) alters the value attached to sleep.
2.5 In an attempt to standardise assessment of sleeplessness, other studies have relied upon operationalised definitions which attempt to quantify the extent of sleep disturbance in terms of the length of time taken to settle to sleep, the number of times a child wakes in the night, how long they are awake for and the number of nights a week upon which these difficulties arise. The frequency and duration of the various problems allow childhood sleeplessness to be classified in broad categories as 'mild', 'moderate' or 'severe' (e.g. Richman & Graham, 1971; Wiggs & Stores, 1996; Montgomery et al., 2004). Assessment of these variables may be by subjective (i.e. parent or child report gathered via interview, sleep diaries or questionnaires) or by more objective recording of the child's sleep pattern (most commonly, using actigraphs, which are movement sensors worn on the wrist from which sleep/wake states can be identified (Sadeh et al., 1994)). Correspondence between these subjective and objective measures is generally good (Sadeh, 1990) although, unsurprisingly, not always without some differences (Acebo et al., 2005). Objective and subjective assessments of sleep measure different aspects of sleep. Both are valuable; in isolation, neither may be sufficient to understand how sleep patterns are linked with daytime lives.
2.6 What all the existing definitions have in common is that they fail to adequately address the interaction between a child's sleep pattern and the parents' beliefs, expectations, values and resources, all of which will be relevant when trying to decide if children are having adequate sleep; adequate sleep may mean different things to different people. As Jennie & O'Connor (2005) have extensively described, the beliefs about what constitutes 'normal' sleep (e.g. amount of sleep, timing of sleep, continuity of sleep) and the sleep-related practices (e.g. bedtime routines, sleeping arrangements, use of sleep-aids) which are considered desirable are subject to significant cultural and historical influence. An inability to settle to sleep alone ceases to be a 'problem' in societies where children are never expected to achieve this ability because collective sleeping is the cultural norm.
2.7 Even within one culture, a mis-match between the expectations and norms for different subgroups (in this instance children and adults) may be pertinent. In some societies, infants' poly-phasic sleep patterns are at variance with the monophasic sleep patterns of most parents. Biologically, the adult circadian alertness rhythm is bi-phasic, with both the night time and early afternoon being times when the propensity to sleep is high. Such a pattern suggests that the afternoon 'siesta', still popular in many countries, has both social/environmental and biological origins and that the monophasic sleep pattern of many adults is also partly socially and environmentally defined (to permit maximum working hours/maximise productivity). It is perhaps the imposition of these socially defined, adult schedules on the child which contributes to children's sleep being considered to be 'problematic'. Children need to be socialised into these patterns but there may well be different rates of readiness to be socialised and 'readiness' may be affected by physiological maturity, psychological state and social factors.
2.8 Sleeplessness problems, whether defined by clinicians, researchers, parents or children themselves cannot be discussed without being mindful of how cultural and personal values need to be considered along with biological sleep requirements. Ideally, an integrated approach to the study of child sleep is needed.
Prevalence of sleeplessness
3.1 Whilst acknowledging these definitional shortcomings one cannot ignore the large body of published data suggesting that 'problems' with children's sleep are widely reported by both parents and children of all ages. Sleep disturbances are one of the most frequently reported behaviour problems affecting children from the general population, with estimated overall prevalence rates of about 30% (Richman, 1981; Owens et al., 2000).3.2 Although it is not possible to estimate the true prevalence of sleeplessness in young people because of the lack of sufficiently thorough epidemiological studies (Richman, 1987) it is apparent that the rate of sleeplessness is high, even for the more severe and persistently occurring disturbances: about 25-50% of 6-12 month olds have difficulty settling to sleep or waking in the night and these figures do not dramatically reduce as the child grows: by age 3 years 25% to 30% have sleeplessness problems with similar percentages reported for the 3 to 5 years age group (Mindell 1993; Mindell & Owens 2003). These problems are not transient; an epidemiological study of a national cohort of 5 year olds suggested that sleeping problems at age 5 years were significantly associated with sleeping difficulties at age 6 months (or before) and that the children with sleep problems age 5 years were more likely to have sleeping problems at 10 years of age (Pollock, 1994).
3.3 Contrary to popular belief, childhood sleeplessness problems are not something which children 'grow out of'. The rate of reported sleep problems does not appear to decrease as children move into the pre-adolescent stage; 43% of 8-10 year olds were reported by Kahn et al., (1989) to have experienced a sleep problem for more than 6 months. Data gathered from a selected group of North American schoolchildren aged 10 to 13 years suggest that the parental report figures may be an underestimation of the problem; 35% of the children stated that they woke once each night and 5% that they woke several times a night (Anders et al., 1978).
3.4 High rates of sleeping difficulty are still reported in adolescence: Bearpark and Michie (1987) surveyed 350 children aged 10-17 years and found that 23% had difficulty falling asleep (a figure which increased with age), 11% woke in the night and waking in the morning was a problem for 18% with only 3% waking too early. The difficulty with which adolescents wake in the morning was supported by the study of 943 adolescents aged 15 years conducted by Morrison et al., (1992). More sleep was said to be needed by 25% of the sample, 10% had difficulty falling asleep, 2% complained of night waking and 3% of early waking. The rates of sleep disturbance remain high throughout childhood and adolescence (although the nature of the most common causes of sleeplessness are likely to change as children mature (Stores, 2001)).
3.5 It is important to remember that there are specific child and adolescent populations which are particularly prone to disturbances of sleep. These include young people with various medical and psychiatric conditions and neurodevelopmental disorders (Stores & Wiggs, 2001). Amongst children with intellectual disabilities up to 86% of children aged less than six years were reported by parents to have 'sleep problems' (Bartlett et al.,1985) with similar high rates (77%) even for children aged 12-16 years. Problems of sleeplessness (i.e., difficulty getting off to sleep, night waking, or early waking) appear, again, to be the most commonly reported problems (Quine, 1991; Wiggs & Stores, 1996a).The reasons why sleep may be disturbed for such children obviously include medical, psychological and physiological factors related to their underlying condition (see Richdale & Wiggs (2005) for a discussion of these factors) but the role of parental (and professional) expectations should also be considered; research has suggested that many parents of children with neurodevelopmental disorders are not surprised that their child has sleep difficulties, viewing the problem as an inevitable part of the child's underlying condition for which they often do not seek help (Wiggs & Stores, 1996b; Robinson & Richdale, 2004). The idea that aspects of sleep are learnt behaviours, shaped by one's social and cultural environment is supported by the evidence that these common, persistent and often severe sleeplessness problems which frequently are present in children with impaired learning are often amenable to behavioural interventions which use techniques to help children learn a desired new set of sleep behaviours (Richdale & Wiggs, 2005).
3.6 When considering the prevalence of sleeplessness in children and adolescents it is helpful to be mindful of the fact that insidious social changes may, over many years, lead to changes in the accepted 'norms' of child sleep, within the Western world. Iglowstein et al's (2003) study has suggested that the total amount of nightly sleep received by children may be decreasing over time. It is important to remember that although reduced sleep may be the 'norm' this does not necessarily mean that reduced sleep is in children's and families' best interests. The social influences responsible for such changes could be broad. For example, several studies suggest that early school start times are associated with children having reduced amounts of sleep and, in turn, increased daytime sleepiness, poorer concentration, attention problems and even impaired academic performance (Epstein et al., 1998; Wahlstrom et al., 2001).
3.7 As another example, computer game playing, internet use, television viewing, possession of mobile phones and socialising have all been linked with reduced sleep and reduced opportunities for sleep (Owens et al., 1991; Tazawa & Okada, 2001; Van den Bulck, 2003; Van den Bulck, 2004). Punamaki et al. (2007 in press) have also suggested that gender preferences for different technologies may also be associated with sleep disruption patterns, so that whilst both genders may be equally likely to have their sleep affected by mobile phone use during early adolescence, for 16-18 year olds this becomes more of a problem for girls and boys' sleep disruption is more clearly linked with computer game playing.
3.8 Asking whether children are getting enough sleep is a question that can be posed at both the societal and the individual level and it is likely that parents' (and children's) judgements of the latter will be at least partially informed by societal norms, and personal values, which will vary across time and cultures.
Impact of sleep disturbance
4.1 In trying to ascertain the impact of sleep disturbance some methodological issues hamper precise interpretation and need to be considered. One area of problem is that studies have used very different methods to assess both sleep and daytime functioning (e.g. from quantifiable objective recordings/performance testing to more richly detailed, but subjective, reports). Whilst this can make it difficult to compare across studies it is precisely this difference of approach which has been valuable in highlighting how child sleeplessness, and its associated problems, can be defined in different, but equally useful, ways.4.2 Perhaps of more concern, is that different studies in the field address sleeplessness of different aetiology (e.g. arising as a result of a medical/psychological sleep disorder, arising in experimental studies of sleep deprivation/restriction, or naturalistically as a result of children/s choices or lifestyle demands). The nature of the sleeplessness, and how it is perceived by the child and the family are likely to vary greatly across categories.
4.3 Of course even within these broad categories the children (and by implication then too the parents and their parenting experiences) are heterogeneous in terms of various important variables. For example, studies have included children aged from a few weeks old to those well into their teens. Developmental expectations and skills are highly salient in this field and more work with children of discrete ages is required. In addition, much of the work addresses groups of children with various neurodevelopmental disorders. Sleep disturbance, and its implications for children and families may be very different for children with and without associated clinical complications.
4.4 Lastly, in contrast, the studies conducted are very homogenous in terms of the cultural groups that they include. As discussed, children's sleep patterns are strongly culturally determined (Jenni & O'Connor, 2005; McLaughlin Crabtree et al, 2005) and there is a need for increased cross-cultural studies to see how far our understanding of child sleep in industrialised western society can be applied to other cultural groups.
4.5 Mindful of these limitations, the previously discussed experimental studies of sleep deprivation/restriction in children have indicated that impaired sleep is associated with adverse effects on cognitive functioning. These experimental studies, typically lasting for a few nights at most, lack external validity in the context of sleeplessness problems, as commonly defined in the psychological, paediatric and medical literature. The latter are typically longstanding and, in adults a least, the cumulative effects of sleep loss have been suggested to be great (Drake et al., 2001; Van Dongen et al., 2003). Apart from the temporal differences between the studies a further significant difference is that, in real-life settings, child sleeplessness typically impacts on the sleep patterns and subsequent daytime functioning of other family members as individuals and, as a result on the family unit. Without prospective longitudinal studies it is, of course, difficult to establish a causal relationship between childhood sleeplessness and impaired functioning of families (at an individual level or as a group). Nevertheless, consistently strong associations have also been reported in naturalistic studies comparing aspects of functioning in children who typically receive different amounts of sleep and also in children with reported (or self-reported) sleeplessness. These data will be examined in this section.
4.6 Sleep patterns in children have repeatedly been shown to be inextricably linked with aspects of a child's daytime functioning. Examining objective sleep patterns in school age children (7-9 years old) has indicated that reduced objective sleep time is associated with teacher (and parent) reports of externalising behaviours (Aronen et al., 2000), daytime sleepiness and depressed mood (Wolfson & Carskadon, 1998) and also with impaired working memory function in 6-13 year olds, after controlling for age (Steenari et al., 2003). Steenari et al. (2003) also found that an extended time to fall asleep and a greater proportion of time in bed spent awake were also similarly linked with working memory function. Measurable deficits in performance at school (i.e. grade point averages) have also been found to be associated with sleep patterns, notably, waking later in the morning, reduced night wakes, longer sleep, napping and reduced sleep latency (Link & Ancoli-Israel, 1995; Kahn et al., 1989; Hofman & Steenhof., 1997). In a large study of over 3,000 13-19 year olds it was found that those students who were 'failing' in terms of their school grades had significantly less sleep (25 minutes), went to bed later (40 minutes) and at weekends tended to go to bed later (and lie-in later). The small absolute differences between the groups (i.e. on average a total of 25 minutes sleep) are in accordance with the results of Sadeh et al.'s (2003) study where similar amounts of change in sleep duration were important determinants of next-day neurobehavioural functioning. Such findings highlight how vulnerable children may be to even relatively minor disruption of sleep patterns. Meijer et al.(2000) failed to demonstrate a relationship between students' (age 9-15 years) self-reported time in bed and their school grades but showed how it is not only school performance which might be affected but also children's self-perception; difficulty getting up in the morning, poor quality sleep and feeling unrefreshed by sleep were all found to be associated with children reporting reduced motivation to do well in school, a more negative image of themselves as students and reduced receptivity to teachers' influence.
4.7 Certainly, sleeplessness problems are often part of a more generalised behaviour disturbance in the child. Daytime behaviour problems have been found in 55% of 1-2 year olds with night waking (Richman, 1981) and in 45% of 3 and 8 year olds (Richman et al., 1982) which is about three times the rate seen in children without sleep problems. Research suggests it to be unlikely that parents who report problematic nighttimes are simply also more likely to report problematic daytime behaviour in their children; parent report of disrupted sleep in preschool children has been found to predict teachers' reports of behavioural problems (Lavigne et al., 1999; Bates et al., 2002). Further, in an older group of nearly 6,000 8-9 year olds children's self reported sleep problems were found to predict teacher reports of the children's emotional problems, behavioural problems, hyperactivity and school attendance (Paavonen et al., 2002).
4.8 A similar relationship between the presence of sleeplessness and elevated rates of daytime behaviour problems has been reported in many groups of children with various developmental disorders (Quine, 1991; Wiggs & Stores, 1996a; Stores et al., 1998; Johnson et al., 2005; Wiggs et al., 2005) and, again, corroboration by teacher report (Wiggs & Stores, 1999) suggests that this relationship is not due to a reporting bias. This is noteworthy because these groups of children may be particularly likely to have high prevalence rates of both sleep and behavioural disturbance, including for organic reasons, yet still such an association exists.
4.9 In addition to these concurrent relationships between sleep and a child's daytime functioning work with typically developing children and adolescents suggests that the presence of sleep problems may be predictive of functioning many years later. For example, a prospective study by Wong et al., (2004) suggested that mothers' ratings of children's sleep problems when aged 3-5 years predicted early drug and alcohol abuse (aged 12-14 years) amongst a sample of children at high-risk for substance abuse. Further, in a large, prospective longitudinal study Gregory et al., (2005) noted that persistent sleep problems during childhood (aged 5, 7 and 9 years) were predictive of anxiety disorder (but not depression) when the sample were aged 21 and 26 years, after controlling for sex, socio-economic status and childhood internalizing problems. Others have found a link between sleep patterns and later depressed mood; van Lang, Ferdinand and Verhulst (2007) found adolescent sleep disturbance to be predictive of depression in young adulthood and that the relationship was particularly strong specific for girls. These somewhat contradictory results concerning links between sleep and subsequent depression perhaps indicate that sleep problems at different stages of development might have different significance and implications for children's development and functioning.
4.10 As intimated earlier, child sleeplessness does not affect children in isolation but also their parents. Mothers of children with sleep problems have received the greatest amount of attention in the research literature. The profound affect on parents of sleepless, crying newborns is highlighted by a large study of Dutch parents of 1-6 month old infants, of whom 6% admitted hitting, shaking or smothering the child during such episodes (Riejneveld et al., 2004). In a smaller, more in-depth study of American mothers 70% admitted to fantasies of aggression and 20% reported that these fantasies extended into actually killing the child (Levitzy & Cooper, 2000). With such extreme emotions being evoked by a crying, sleepless child it is perhaps unsurprising to see that a higher incidence of depression and anxiety and stress have been identified in the mothers of sleepless children (Lozoff et al., 1985; Cunningham et al., 1986; Zuckerman et al., 1987; Quine, 1992a; Armstrong et al., 1998; Hiscock & Wake, 2001; Gregory et al 2005). Those mothers of children with sleep problems are more likely to have an attitude of ambivalence to the child (Lozoff et al., 1985) and to have a profile of cognitions about child sleep which includes believing that they have difficulty setting limits, anger at the child's demands and doubts about their parenting competence (Morrell, 1999). Subsequent studies with older children with autism (Wiggs & Stores, 2002) and Attention Deficit Hyperactivity Disorder (Montgomery et al., submitted for publication) have also found differences in the cognitions of parents of children with and without sleeplessness problems but different profiles of cognitions have been found in parents from each of these groups, perhaps reflecting how parents' cognitions about child sleep may be driven by aspects of the child other than their sleep pattern per se.
4.11 Similar associations between child sleep patterns and mothers' mental health have been found in mothers of children with learning disabilities and sleep problems, e.g. increased stress, irritability, and more negative views of their spouses, their child and themselves (Quine, 1991; Quine, 1992b; Cunningham et al., 1986; Richdale et al., 2000). The severity of the sleep problem is also important as the more severe the sleep problem the more the parents considered their child to have an impact on family life and daily functioning (issues not directly related to sleep) although the stress levels of parents were as elevated when sleep problems were 'mild' as when they were 'severe' (Quine, 1992a). The presence of a learning disabled child in these families may be expected to result in more challenges for parents anyway, and the additional problem of sleep difficulties appears to compound their problems and increase the burden of care.
4.12 The associations between child sleeplessness and fathers' psychosocial functioning has been less explored. Richman (1981) suggested that compared to mothers of good sleepers, mothers of sleepless children were more likely to report the children's fathers as being unsupportive and difficult to confide in. More recently, Wiggs & Stores (2001) demonstrated gender differences in response to sleeplessness amongst fathers and mothers of children with intellectual disabilities, with mothers appearing to be more stressed and fathers more likely to suffer from daytime sleepiness. Considerably more attention needs to be given to fathers in relation to childhood sleeplessness to aid understanding of how fathers are affected and how they may influence the family dynamics which may cause, result from or prevent sleeplessness and its associated difficulties for children and families.
4.13 The effects of sleep problems on the family unit were suggested to be serious by Chavin and Tinson (1980) who interviewed parents of children aged 8-36 months: 37% felt the sleep problem had caused serious arguments, 8% admitted severely abusing their child and 2% attributed the break up of their marriage directly to the child's sleep problem. Increased rates of marital difficulties (Richman, 1981; Quine, 1992b; El Sheikh et al., 2006), parental violence (Haslam, 1992; Baldwin & Oliver, 1975) and family disorganisation (Gregory et al .,2005) have also been reported.
4.14 Although the causal direction cannot currently be established, it can be concluded that childhood sleeplessness problems have repeatedly been shown to be associated with adverse effects on mothers and family functioning. Research examining the links between child sleep patterns and fathers' functioning is very preliminary and this is an important area for future work. Research utilising a prospective longitudinal design is a helpful preliminary approach for investigating the order of effects and, for example, has recently been used successfully to demonstrate a dose-response relationship between family conflict during childhood and insomnia in adults aged 18 years (Gregory et al., 2006).
Impact of treatment for sleep disturbance
5.1 Of note is that many of the adverse effects can be reversed by removal of the sleep disturbance, emphasising the importance of addressing sleep disturbance as a means of perhaps improving overall functioning of the child and family unit.5.2 Behavioural therapy (i.e. using strategies designed to help children to learn new sets of behaviours and un-learn undesirable behaviours) is the treatment of choice for most sleeplessness problems in typically and atypically developing children and adolescents (Owens et al., 2002, Kuhn & Elliot, 2003; Owens et al., 1999; Ramchandani et al., 2003; Wiggs & France, 2000; Richdale & Wiggs, 2005).
5.3 Successful behavioural therapy (both with typically and atypically developing children) has repeatedly been associated with reductions in child problem behaviour (Seymour et al., 1983; Sanders et al., 1984; Quine, 1992b; Dahl et al., 1991) and improvements in parental mental health and marital satisfaction (Durand & Mindell, 1990; Quine, 1992b; Wiggs & Stores, 2001; Hiscock & Wake, 2002) and in mothers' objective sleep patterns (Wiggs & Stores, 1998). In Quine's (1992b) intervention study with learning disabled children, post-treatment the mothers reported being less irritable with the child, smacking them less often, feeling more positive about their child, their partner and themselves, feeling less stressed and having higher morale.
5.4 Even used preventively significant effects on parenting stress, sense of efficacy and parental sleep have been documented (Wolfson et al., 1992). Following intervention more positive interactions with the child have been both reported by parents (Quine, 1992b) and independently observed in some specific settings (e.g. during feeding) (Minde et al., 1994). However, a minority of studies have failed to find any associated changes (e.g. Richman et al., 1985) or have documented positive changes in both control and treatment groups (Wiggs & Stores, 1999) suggesting that further work is needed to fully understand the complex relationship between child sleep problems, their treatment and the functioning of family members. It may be that there are, as yet undiscovered, protective or pre-disposing factors which affect outcome or treatment response.
5.5 The mechanisms by which any improvements in child and family functioning arise are also of interest. Wiggs and Stores (1998) reported that intervention for sleeplessness problems in school age children with intellectual disabilities resulted in objective improvements in mothers' sleep which preceded objective changes in the children's sleep. Another study of school aged children with autism spectrum disorders (Wiggs & Stores, 2006) reported no objective changes in children's sleep, despite reported improvements in child behaviour. Such findings suggest that it is possible that in addition to, or even instead of, reversing the effects of sleep deprivation in children, intervention for childhood sleeplessness may have a primary effect on other factors within the family, including the sleep and subsequent daytime functioning of the mothers and that this might lead to changes in how mothers interact with their children and spouses. Such a hypothesis has implications for how one might 'intervene' to help children and their families.
5.6 Two comments of mothers of children with autism, who took part in a behavioural intervention study are revealing. One mother commented that the resolution of her child's sleeplessness problem had given her 'her evenings back'. Here, very direct effects upon the daily life of the mother are shown to be related to her child's sleep. Another mother said that 'for the first time I am able to say goodnight to my child and it is a pleasant experience'. Here, the more emotional implications of an intervention are touched upon. The introduction of this new and pleasant end to the day might be expected to impact emotionally on both the mother and child individually and also on the dyad's relationship and interactions.
5.7 Of note is that one study suggests that the effects of successfully resolving a child's sleeplessness problem may be gendered. Wiggs and Stores (2001) reported that, following intervention, mothers of children with intellectual disabilities and sleeplessness benefited from reduced stress, increased perceived control and more satisfaction with their sleep, their child's sleep and their ability to cope with their child's sleep. However, benefits for fathers were limited to increased satisfaction with their sleep and their child's sleep and indeed there was a significant reduction in their feelings of perceived control. This reduction in feelings of control is hypothesised to be due to the fact that mothers took a more active role in the intervention process; as mothers gained new skills fathers were in effect de-skilled. This stresses how it is the interactions between family members which need to be explored in future studies.
Family context of sleeplessness
6.1 The research discussed so far strongly suggests that children who do not get adequate sleep are likely to show impaired neurobehavioural functioning, relative to how they might function with adequate amounts of good quality sleep. These 'direct' effects of sleep loss need to be avoided to ensure that every child, parent and family unit has the opportunity to reach their full potential. However, it must also be remembered that childhood sleeplessness is more than a quantitative phenomena it is also a behavioural state which exists in a family context and which exists reciprocally with other features of the family members and unit.6.2 Conceptualising adequate child sleep needs to be based upon both a child's individual sleep needs (i.e. the amount required in terms of physical and psychological restoration) and the parental/child definition of adequate sleep, based as it is on socio-cultural expectations. Both can be different but both may be associated with effects upon child and family function.
6.3 Morrell (1999) demonstrated how using research criteria (based upon the frequency and duration of a child's sleeplessness) may identify different children when compared to using simple maternal criteria (i.e. asking mothers to rate the overall severity of their child's sleep problem on a four point scale of 'no problem', 'mild' 'moderate' or 'severe'). A proportion of children with less frequent or shorter duration sleeplessness problems were not classified as having problematic sleep according to the research criteria yet were considered by mothers to have significant problems. Other researchers have found similar results (Scott and Richards, 1990). These data support the idea that objective sleep/waking behaviour may be only one of the factors which need to be considered when evaluating children's sleep patterns and that also how the child's sleep pattern impacts upon a mother (and other family members) is a distinct, but important additional factor to consider. The social validity of relying on the concept of maternal definitions of child sleeplessness is supported by the data showing that maternal stress associated with child sleeplessness is not related to the severity of the child's sleep problem; mild problems are equally as stressful as severe problems (Quine, 1991).
6.4 Of course, the opposite situation may occur, where parents definitions of 'problems' may be more conservative than the research criteria (Wiggs & Stores, 1998). In a study sample of over 100 families of school aged children with learning disabilities the authors found three groups; mothers who considered their child to have no sleep problem (and the child did not, according to research criteria) ('no sleep problem' or NSP group); mothers who considered their child to have a sleep problem (and the child did, according to research criteria) ('sleep problem' or SP group); and mothers who considered their child not to have a sleep problem (and the child did have one, according to research criteria) ('unrecognised sleep problem' of USP group). The USP and NSP mothers and children were similar in many important respects. Compared to the SP group the mothers were less stressed (the SP group all had critically high levels of clinical significance), had increased perceived control, perceived their partner as having higher levels of control and the children had fewer daytime behaviour problems (as rated by both mothers and teachers). Interestingly, the USP and SP mothers were both equally dissatisfied with their child's, and their own, sleep pattern. The results suggest that the USP mothers were not unrealistic about the objective sleep patterns of their child but that there might be factors (e.g. more parental perceived control, reduced levels of daytime behaviour problems in their children) which allow them greater resilience and enable them to conceptualise the child's sleep pattern as 'unproblematic'.
6.5 Of course, the factors that might be relevant to parents' judgements are not yet adequately delineated. The above study highlights some possibilities of variables in the mother and child, but other family members (e.g. fathers, siblings, extended family) and other support networks need to be investigated. It seems reasonable to expect that interactions in protective and predisposing factors (both between and within family members) contribute to parents' judgements about the status of their children's sleep patterns. Cultural differences in beliefs and practice (relating to both child sleep but also to daytime functioning of the child and family) are likely to mediate.
6.6 Importantly, the results suggest that mothers who consider their child to have a sleep problem are likely to be those who are perhaps most of need of help since they suffer extreme stress levels. Clinically, this is encouraging in some ways as it is most likely that it is those mothers who consider their child to have a sleep problem who are most likely to ask for assistance from health professionals. However, do mothers who do not consider their children's sleep to be problematic (even though the children have disrupted sleep) also ask for assistance? And if not, what are the implications for the children and their parents? These questions need to be addressed in future studies.
6.7 The above results suggest that perhaps it is too simplistic to ask 'are children getting enough sleep?' because 'enough sleep' is a vague concept. Child sleeplessness might be better theoretically conceptualised as comprising two distinct states with different causes and effects. Firstly, a `biologically-defined sleeplessness` characterised by a child having objectively impaired sleep quantity or quality, relative to their biological sleep needs. Secondly, a 'socially-defined sleeplessness' characterised by the child's sleep pattern deviating from a desired sleep pattern. Judgements about what constitutes a 'desired' sleep pattern will be influenced by multiple factors including expectations and culture. Both of these states may exist independently, or co-exist. Further, socially-defined childhood sleeplessness may be described by parents or by children themselves.
6.8 Even within these two basic states further subdivisions will exist, again with implications for causes and effects. Scientific research has clearly described how different forms of biologically defined sleep disruption (e.g. total sleep deprivation, reduced sleep quantity, fragmented sleep) result in different forms of impairments in adults (Bonnet, 2005) but this remains to be properly explored in children (Fallone et al, 2002). However, socially-defined sleeplessness may also be divided in a similar way highlighting 'problems' with going to bed, going to sleep, waking in the night, waking early in the morning, sleeping arrangements etc. These different areas of sleep conflict may be associated with different social issues for parents and children.
6.9 A thorough exploration of the sleep adequacy of children needs to measure both biological and socially defined sleeplessness, in both parents and children and to be able to examine how these states and their effects, interact and impact upon all members of the family.
Conclusion
7.1 The experience of inadequate and/or poor quality sleep in children is something which is commonly reported both by parents and also, in a smaller number of studies, by children themselves. There is repeated evidence to suggest that childhood sleeplessness defined objectively (in terms of reduced sleep, atypical sleep patterns and extended wakefulness) or subjectively (by means of reported 'problems') appears to be associated with impaired neurobehavioural functioning of children and poorer psychological health and functioning of mothers, family units and possibly fathers too. As such, this is an area of priority and we should aim to understand why sleep disturbance is widespread, how this complaint affects individuals and their families and how best to alleviate the disturbance and associated difficulties.7.2 From a theoretical level it seems clear that that childhood sleeplessness can be conceptualised as being potentially both biologically and socially determined, and the impact of these different forms of sleeplessness are likely to be caused by distinct, but possibly overlapping, pathways. As such, whilst it is, of course, important to be asking whether or not children are getting enough sleep we should perhaps also be asking whether or not parents are getting adequate sleep as the answer to this question may have implications for children via the functioning of family members and the family unit.
7.3 Such an approach acknowledges that the mechanisms underlying 'successful' behavioural interventions for sleeplessness are likely to be complex and importantly from a clinical perspective, suggests that there may be novel intervention (or prevention) approaches for childhood sleeplessness which are beneficial for families, and children but which do not impact upon the objective sleep patterns of children.
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