Any review of adolescent lifestyles in our society will reveal more than a dozen forces converging to push the sleep/arousal balance away from sleep and toward ever-higher arousal. What harm could there be in trying to push back a little toward valuing sleep?
In this article I provide an overview of current scientific and clinical information regarding the consequences of insufficient sleep in adolescents. I pay particular attention to links between sleep and emotional regulation. The following is a brief outline of the main points to be presented:
1. Sleepiness. This is the most direct consequence of adolescent sleep loss, and it manifests itself most significantly in difficulty getting up on time for school and in falling asleep in school. These problems can further contribute to conflicts with parents and teachers and to poor self-esteem. Sleepiness is also associated with a strong tendency toward brief mental lapses (or microsleeps) that greatly increase the risk of motor vehicle and other kinds of accidents.
2. Tiredness. This is a symptom of sleep loss and includes changes in motivation - particularly difficulty initiating behaviors related to long-term or abstract goals and decreased persistence in working toward goals.
3. Mood, attention, and behavior. Sleep loss can have negative effects on the control of mood, attention, and behavior. Irritability, moodiness, and low tolerance for frustration are the most frequently described symptoms in sleep-deprived adolescents. However, in some situations, sleepy teenagers are more likely to appear silly, impulsive, or sad.
4. Impact of emotional and behavioral problems. ?motional arousal and distress can cause both difficulty falling asleep and sleep disruptions. Behavioral problems and family chaos can contribute to even later bedtimes and to sleep schedules that are ever more incompatible with school schedules.
5. Bi-directional effects. There are bi-directional effects between sleep and behavioral/emotional problems. It can be difficult at times to identify the causal links. For example, a depressed adolescent with severe sleep problems may be showing sleep disturbances that stem from depression or mood problems that stem from sleep disruption. Sleep loss can also contribute to a negative spiral or vicious cycle of deterioration. That is, sleep loss can have a negative effect on mood and behavior, which leads to subsequent emotional/behavioral difficulties that further interfere with sleep. This produces a sequence of negative effects in both domains. In some clinical cases, such negative spirals appear to be a pathway to withdrawal from school or serious psychiatric problems. (Dahl, pp.43)
Before discussing the specific consequences of insufficient sleep in adolescents, it is necessary to begin with a general overview on what sleep is and why it is necessary at all. Sleep is not simply rest. Mere rest does not create the restorative state of having slept. (Anyone who doubts this should try the following experiment tonight: spend eight hours resting in bed, with eyes closed, body relaxed, mind floating, in a deeply tranquil state, but without ever going to sleep; then keep track of your mood and performance tomorrow.) The fundamental difference between sleep and a deeply relaxed wakefulness is that sleep involves dropping into a state with a relative loss of awareness of and responsiveness to the external world. This state of unresponsiveness appears to be necessary for the restorative processes that occur during sleep to take place.
Furthermore, sleep itself is an active process. Sleep involves dynamically changing patterns and progressive stages, with some brain regions showing a great deal of activity in some sleep stages. Moreover, there are several aspects of sleep necessary for full restoration, including the continuity, timing, and patterning of different stages of sleep, as well as the timing of the sleep in relation to other biological rhythms.
Sleep is not some biological luxury. Sleep is essential for basic survival, occurring in every species of living creature that has ever been studied. Animals deprived of sleep die. (?xperiments with rats show that they can survive without sleep for about as long as they can survive without food.) Yet the specific function of sleep - why it is necessary for survival - remains a scientific mystery and the focus of a great deal of investigation. Within this scientific mystery, however, are two important clues that are relevant to discussions of sleep and adolescent health. First, sleep seems to be particularly important during periods of brain maturation. (Across species, maturing individuals sleep more than fully mature individuals.) Second, sleep is naturally restricted to times and places that feel safe. Most species have evolved mechanisms to ensure that sleep is limited to such safe places as burrows and nests and to times of relative safety from predators. In humans, there is a similar tendency for safe feelings to promote sleep while feelings of threat or stress tend to inhibit sleep.(Dahl, pp.65)
These links between sleep and stress are an important source of sleep disruption among adolescents. A key point can be best illustrated by a brief consideration of the evolutionary underpinnings of these biological links between sleep and emotion. For most of early human history, large nocturnal-hunting carnivores surrounded our ancestors, who had no access to physically safe sleep sites. (Humans cannot sleep in trees or on cliff edges, because we lose all muscle tone during R?M sleep.) (Horne, pp.15) In the human ancestral environment, the main protection against predators was a close-knit social group. The human brain evolved under conditions that made this sense of social belonging and social connectedness the basis for feelings of relative safety. Natural tendencies in the human brain continue to reflect these links, so that fears of social rejection can evoke powerful feelings of threat and so lead to sleep disruption, while feelings of love, caring, and social connection create a feeling of safety and so promote sleep.
Finally, it is important to consider the ways in which the sleep and vigilance systems change during adolescent development. The maturation of humans during puberty includes physical and mental changes in preparation for taking on adult roles (with increased demands for threat appraisal and response). Changes in the vigilance system include a greater capacity for sleep disruptions from social stresses, including fears, anxieties, and emotional arousal.2 Thus adolescent sleep systems appear to become more vulnerable to stress at a time when social turmoil and difficulties are often increasing.
There is a surprising lack of controlled studies examining the effects of sleep deprivation or insufficient sleep among adolescents. However, there is extensive circumstantial evidence, clinical evidence, and research in adults that is relevant to these questions. While there is a general convergence of these findings, one important caveat is that we need a greater number of direct investigations. A second note of caution is that we lack information about long-term or chronic effects of insufficient sleep, since the limited data available have addressed only the immediate and short-term effects of sleep loss.
Perhaps the best-studied example of such interactions is the relationship between sleep and depression. Subjective sleep complaints are very common in children and adolescents who have been diagnosed with Major Depressive Disorder (MDD). Symptoms include insomnia (75% of cases) and hypersomnia (25%). Hypersomnia difficulties are reported more frequently after puberty. Insomnia symptoms usually include difficulty falling asleep and a subjective sense of not having slept deeply all night. (Horne, pp. 45)
In brief, there are four main effects of acute sleep loss: 1) sleepiness, 2) motivational aspects of tiredness, 3) emotional changes, and 4) alterations in attention and performance. (Dahl, pp.112) Before discussing each of these briefly, I wish to stress one general principle that applies across categories: the influence of effort. That is, the effects of sleep deprivation can be offset or even overridden for short periods of time by increased effort (or by increasing the external motivation to perform through rewards or punishments). The good news here is that most capabilities can be maintained over a short interval if necessary, while the bad news is that everything is harder to do. In some ways this is the cardinal feature of sleep deprivation: it takes increased effort to perform the same cognitive, emotional, or physical tasks. Frequently in this article I have cautioned readers about the need for additional research to improve our understanding of the complex issues arising from the consequences of insufficient sleep among adolescents. Our current knowledge is preliminary and based on a paucity of controlled data. Furthermore, we are probably at an equally early stage in our understanding of the behavioral and emotional problems of adolescents.
Nonetheless, behavioral and emotional difficulties are currently the largest source of morbidity and mortality among adolescents. While it is possible that sleep loss makes only a minuscule contribution to adolescents' problems with emotional regulation, it is extremely likely that it plays some role. It is also quite possible that insufficient sleep plays a significant role in leading up to some of these problems in a vulnerable set of individuals. Identifying vulnerability to sleep loss may represent an important future direction for research, since there appear to be such large individual differences in the effects of acute sleep loss. Such vulnerability could be related to a tendency to need more sleep, to being a "night owl," or to a biological vulnerability toward emotional disorders. Clearly, more research is needed to help inform policy makers, whose decisions will further affect adolescent sleep patterns. Cost-benefit analyses regarding the relative importance of sleep will require more precise quantification in these areas. In the meantime, one might make a reasonable case that the odds are heavily in favor of sleep as an increasingly important health concern among adolescents. To reiterate the main point with which I began, adequate sleep is defined as the amount necessary for optimal daytime functioning. It appears that the potentially fragile underpinnings of adolescent social competence (controlling thoughts and feelings at the same time) may be most sensitive to the effects of inadequate sleep. Any review of adolescent lifestyles in our society will reveal more than a dozen forces converging to push the sleep/arousal balance away from sleep and toward ever-higher arousal. What harm could there be in trying to push back a little toward valuing sleep? The potential benefits seem enormous.
Bibliography
1. Ronald ?. Dahl, "The Regulation of Sleep and Arousal: Development and Psychopathology," Development and Psychopathology, vol. 8, 1996, pp. 3-27.
2. James A. Horne, "Human Sleep, Sleep Loss, and Behaviour Implications for the Prefrontal Cortex and Psychiatric Disorder," British Journal of Psychiatry, vol. 162, 1993, pp. 413-19.
