| | High Exercise Levels Are Related to Favorable Sleep Patterns and Psychological Functioning in Adolescents: A Comparison of Athletes and ControlsReceived 3 February 2009; accepted 19 June 2009. published online 18 August 2009.
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Adolescents and Emerging Adults' Sleep Patterns: New Developments
Amy R. Wolfson
Journal of Adolescent Health
February 2010 (Vol. 46, Issue 2, Pages 97-99)
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Abstract PurposeTo investigate whether chronic vigorous exercising is related to improved sleep and psychological functioning, and whether this association varies with gender. Both lay and scientific opinions hold that physical activity is an efficient remedy and preventative measure for poor sleep. However, empirical evidence on adolescents is very limited. MethodsA total of 434 adolescents (258 athletes, 176 controls; mean age 17.2 years) took part in the study. Weekly hours spent exercising were 17.69 hours and 4.69hours, respectively. To assess sleep patterns and psychological functioning, participants completed a sleep log for 7 consecutive days and several self-rating questionnaires. ResultsCompared with controls, athletes reported better sleep patterns including higher sleep quality, shortened sleep onset latency, and fewer awakenings after sleep onset, as well as less tiredness and increased concentration during the day. Athletes reported significantly lower anxiety and fewer depressive symptoms. Compared with males, females reported fewer variations in sleep. Male controls had particularly unfavorable scores related to sleep and psychological functioning. ConclusionsFindings suggest that chronic vigorous exercising is positively related to adolescents' sleep and psychological functioning. Results also indicate that males with low exercise levels are at risk for increased sleep complaints and poorer psychological functioning. Adolescence is characterized by important changes in sleep behavior. Even though adolescents still require 9 to 10hours of sleep per night [1], [2], the total sleep time decreases to 6.5–8.5hours during school nights [1], with delayed bed times [3] and an increasing gap between school nights and weekend nights [1], [4]. Furthermore, daytime sleepiness (20%) and insomnia symptoms (25%) are common among adolescents [3], [5], with an increased risk for female adolescents [6], [7]. There is a bi-directional relationship between acute [8] and chronic [9] sleep disturbances and poor physical and psychological functioning. Poor sleep affects quality of life, routine daily functioning [10], and academic performance [11]. In contrast, socio-cultural (e.g., leisure activities in the evening) and psychological factors (e.g., conflicts in families [1], [2], [4]) may compromise adolescents' sleep. To cope with poor sleep, clinical experience indicates a growing reliance on substances, either to induce sleep (alcohol, cannabis) or to reduce daytime sleepiness (caffeine). Psychotherapeutic treatments of insomnia have proved successful but require professional intervention. In contrast, many lay people, physicians, and sleep experts alike regard exercise as an effective and inexpensive means of preventing and reducing sleep problems [12], [13]. However, the scientific basis for these expectations is weak. In addition, with respect to adolescence and gender, there are almost no relevant findings. To explain the impact of exercising on sleep, two main rationales are advanced. According to the first, physical activity leads to physiological changes favorable to homeostatic sleep regulation, for which slow-wave sleep intensity is generally used as a marker [14]. Then, acute exercise seems able to stabilize the circadian system and to reduce daytime sleepiness [15]. According to the second, the positive influence of exercise on sleep may be mediated by general psychological functioning, because exercise is associated with reduced symptoms of depression [16] and anxiety [17], increased self-esteem [18], and psychological well-being [19], [20]. Thus, although there is abundant evidence that physical activity is favorably associated with psychosocial and physiological processes, this is not the case for sleep. For example, acute exercise increased slow wave sleep and reduced stage 2 sleep among 13-year-old adolescents [21], and two other studies reported that higher exercise levels were associated with improved subjective [22] and objective adolescent sleep [24]. However, field studies have generally failed to show sleep-promoting effects in healthy young and elderly people [14], [15], [17]. Thus, further research is particularly important because poor sleep has a tremendous impact on mental health, to the extent of a possible link to suicide attempts [24], and because female adolescents are at increased risk for developing both sleep and affective disorders [6], [7], [25]. Consequently, if it turns out that regular physical activity is favorably related to adolescents' sleep, regular physical activity should be promoted even more strongly [26]. Particularly, this holds also because once a child has started with physical activity regularly, this habit remains fairly stable across the lifespan [27], [28]. Three hypotheses were formulated: (1) we expected favorable sleep patterns in adolescent athletes, compared with controls; (2) we anticipated better scores for psychological functioning in athletes than controls; and (3) we expected increased sleep complaints among female controls, compared with both male participants as a whole and female athletes. Methods  Sample A total of 434 adolescents (age: mean=17.2, SD=1.4) took part in the study. Of these, 258 were athletes. Athletes and activities were as follows: female athletes: N=139, volleyball: n=56 (40.3%); skiing [snowboarding, downhill, cross-country skiing]: n=31 (22.3%); track-and-field athletics: n=19 (13.7%); soccer: n=16 (11.5%), swimming: n=9 (6.4%); other sports disciplines: n=8 (5.8%). Male athletes: N=119; soccer: n=49 (41.2%); ice hockey: n=27 (22.7%); skiing [snowboarding, downhill, cross-country skiing]: n=24 (20.2%); swimming: n=10 (8.4%); martial arts [judo, karate, boxing], fencing, equitation, other sports disciplines: n=9 (7.6%). In all, there were 139 females (mean age=17.0 years, SD=1.3 years) and 119 males (mean age=16.9 years, SD=1.4 years). In addition, there were 176 controls (139 females [mean age=17.1 years, SD=1.3 years] and 37 males [mean age=17.0 years, SD=1.7 years]); gender distribution was as follows: χ2(1)=28.63, p < .001; age: ANOVAs: group, gender, and group×gender interaction: all Fs <1.01, ps > .34). Procedure Adolescent athletes were recruited from “Swiss Olympic Classes” in the German speaking part of Switzerland. The aim of these classes is to provide young athletes the opportunity to continue with high school while training to a high standard in their athletic specialism. To attend a “Swiss Olympic Class,” the adolescent athlete must exhibit high national performance, although not necessarily an international performance. Controls were recruited in the Cantons of Basel and Basel Land, two districts of the German-speaking northwestern part of Switzerland. The heads of four high schools gave permission to recruit students from their high schools. All eligible students were informed about the purpose of the study and about the voluntary basis of their participation. All participants were assured of the confidentiality of their responses and gave informed consent. Parents' informed consent was required for students aged less than 18 years. Of the 491 students approached, parents of 19 students did not give informed consent (3.86%), and 38 students (7.74%) provided incomplete data. Thus, data were available from 434 students (88.39%). Participants completed several psychological and sleep-related questionnaires as described below, and they kept a sleep log for 7 consecutive days, covering 5 school days and 2 off-school days. Participants completed the questionnaires in about 30minutes during class (range 20–40minutes), whereas they completed the sleep log at home. Materials Exercise participation Level of habitual exercise participation was assessed via a self-administered, 7-day log asking students about the amount of exercise (in hours) originating (1) from participation in physical exercise lessons (resulting in increased heart rate and perspiration) and (2) from participation in sports (with the goal of becoming more physically skilled or fit). The scores of the 7 consecutive days were summed up to obtain the total hours of exercise. Results were as follows: female athletes: mean=17.09, SD=5.97, male athletes: mean=18.39, SD=5.23; female controls: mean=4.68, SD=2.09, male controls: mean=4.73. SD=1.20; ANOVA: group: F(1, 430)=667.08, p < .001; gender: F(1, 430)=1.79, p=.18, group×gender F(1, 430)=1.55, p=.21). Sleep The sleep log was based on the Pittsburgh Sleep Quality Index (PSQI [29], German adaptation [30]). Participants were asked to fill out the log consecutively twice a day for 1 week, in the evening and in the morning. For evenings, participants answered questions on an eight-point visual analogue scale about tiredness during the day (8=not at all tired), concentration during the day (8=very good concentration), and mood at bed time (8=very good mood). For mornings, the questionnaire asked about mood on waking (8=very good mood), sleep quality (8=very good sleep quality), and feeling of being restored (8=completely restored), using the same analogue scale (Cronbach's alpha=.92). In addition, sleep onset latency (in minutes), the number of awakenings, and the total sleep time (in hours and minutes) were requested. Interclass correlations showed a high stability between school nights (if participants went to school the following day) and school-off nights (Friday and Saturday nights). Therefore, data for all 7 nights were collapsed into one composite variable (r > .85). Psychological functioning Depression Scale The Depression Scale [31] consists of 16 items and asks about typical depression-related symptoms such as depressed mood (“I feel more depressed in the mornings”), lack of satisfying social interaction (“criticism does hurt me more than before”) and leisure activities, hopelessness (“I often feel abysmal”), and sleep complaints. (To avoid artificial correlations with other instruments related to sleep, the item related to sleep complaints was omitted.) Answers are given on four-point rating scales ranging from 1 (not at all true) to 4 (definitely true). The higher the overall score, the more pronounced the depressive symptoms (Cronbach's alpha=.91). State-Trait-Anxiety Inventory The State-Trait Anxiety Inventory [32] asks about current (state) and chronic (trait) anxiety symptoms. Typical items are: “I feel tense” (state anxiety); “I feel relaxed”, “I'm happy” (trait anxiety). Answers are given on four-point rating scales ranging from practically always to practically never (scoring is reversed for some items). Higher mean scores reflect greater state or trait anxiety (Cronbach's alpha=.89). Everyday stress A self-administered questionnaire asking about stress was applied. The entry question was: ”Within the last four weeks, I have been concerned about… ,” followed by the statements: “… life in the family,” “…relations with peers,” “…relations with my best friend,” “… physical health,” “…my appearance,” “…the future,” “… my performance at school,” and “… my performance at sports” (Cronbach's alpha=.80). Answers were given on a four-point rating scale ranging from 1 (not at all true) to 4 (definitely true), with higher scores reflecting a greater amount of stress in every day life. Sleep-related personality traits Participants also completed a sleep-related personality questionnaire, specifically designed to assess personality traits of patients with sleep complaints (FEPS-I and II [33]). The FEPS-I questionnaire consists of 64 items describing six sleep-related personality traits and subjective sleep quality. Answers are given on a 5-point scale ranging from 1 (not at all true) to 5 (completely true). The dimensions addressed are displayed in Table 1. Higher scores reflect more favorable qualities (e.g., subjective sleep quality: regenerative, undisturbed, unimpaired; Cronbach's alpha=.87). The FEPS-II questionnaire consists of 23 items with the following dimensions. “Focusing” refers to the tendency for a person to think constantly about their difficulties in getting to sleep, remaining asleep, waking up early in the morning and/or suffering from increased daytime sleepiness. “Rumination” refers to the tendency for a person to think continuously about and feel preoccupied with unresolved problems (Cronbach's alpha=.89). | | |  | Dimensions | Poles | |
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| | Favorable pole | Unfavorable pole | |
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| FEPS I | | | | | Attitude toward life | Satisfied, confident, positive | Depressive, dissatisfied, resigned, lacking emotion | | | Self-confidence | Self-confident, resolute, carefree | Anxious, unsure, indecisive, easily irritated | | | Mental arousal | Relaxed, balanced, calm | Tense, irritable, exhausted, burdened | | | Physical arousal | Relaxed, balanced, without any complaints | Nervous, overagitated, complaining | | | Aggressive behavior1 | Externalizing, competitive, asserting own opinion | Internalizing, overcontrolling, inhibited, evasive | | | Self-perception of body sensations | Easy-going, carefree, confiding | Hypochondriac, complaining | | | Subjective sleep quality | Regenerative, undisturbed, unimpaired | Impaired, disturbed, not regenerative | | | FEPS II | | | | | Focusing | Easy-going, carefree, confiding with regard to sleep | Concerned about sleep; preoccupied about not falling asleep, not sleeping enough to feel restored | | | Rumination | Optimistic about coping with problems | Concerned and preoccupied about unresolved problems | | | | |
| 1 The expression “aggressive behavior,” proposed by the test authors, may be misleading; perhaps the dimension should be translated as “assertive behavior.” |
The sleep-related personality questionnaire was chosen because its psychometric properties were satisfactory [33] and because it is applicable both for patients with sleep disorders and for adolescent subjects [34]. The dimensions assessed with these four questionnaires were summarized as psychological functioning, in which high psychological functioning indicated low depressive and anxiety symptoms, low everyday stress, and favorable personality traits. Statistical analyses Several analyses of variance were performed with the factors group (athletes, controls) and gender (females, males). Multiple regression analyses with a stepwise exclusion procedure were performed to predict sleep quality, concentration, and tiredness during the day as a function of group, gender, psychological functioning (stress, depressive symptoms, state anxiety, trait anxiety, aggressive behavior, attitude toward life, self-confidence, mental arousal, physical arousal, self-perception of body sensations, focusing, rumination; “subjective sleep quality” was excluded to avoid artificial associations), and level of exercise. Test results with an alpha error of less than .05 were reported as significant. Results Sleep patterns in athletes and controls Table 2 provides an overview of the descriptive and inferential statistics for sleep patterns extracted from the daily sleep log, as a function of group and gender. First, group differences are highlighted. | ∗ p < .05. ∗∗p < .01. ∗∗∗p <. 001. |
Compared with controls, athletes had higher scores for mood (morning and evening), sleep quality, and restoring sleep. In addition, athletes had shortened sleep onset latency, a smaller number of awakenings after sleep onset, higher concentration during the day, and lower tiredness during the day. No statistically significant group differences were found for total sleep time. In sum, compared with controls, athletes reported more favorable sleep patterns. Psychological functioning in athletes and controls Table 3 provides an overview of the descriptive and inferential statistics for psychological functioning (depressive symptoms, stress, state and trait anxiety, and sleep-related personality traits) as a function of group and gender. First, group differences are highlighted. | ∗ p < .05. ∗∗p < .01. ∗∗∗p <. 001. |
With respect to psychological functioning, compared with controls, athletes had lower scores for depressive symptoms and trait anxiety. No statistically significant group differences were observed for state anxiety and stress. Compared with controls, athletes had more favorable scores on all dimensions of sleep-related personality traits. In sum, the general pattern of results was such that athletes had better psychological functioning than controls. Sleep patterns and psychological functioning, separated by gender Table 2, Table 3 also give the break-downs by gender for dimensions of sleep patterns and psychological functioning. With respect to sleep as assessed with the sleep log (Table 2), compared with male participants, female participants reported more awakenings after sleep onset and lower scores for restoring sleep. For all other sleep dimensions, there were no statistically significant differences by gender. Significant group×gender interactions revealed that females' sleep quality and mood (evening) remained stable between the groups, whereas the lowest scores were observed in the male control group. With respect to psychological functioning (Table 3), compared with males, female participants had higher scores for depressive symptoms, stress and trait anxiety, but less state anxiety. Moreover, females reported more assertive behavior, less physical arousal, less self-perception of body sensations, and a lower sleep quality. Group × gender interactions showed the following pattern of results: male athletes had higher (i.e., “better”) scores for self-confidence, physical arousal, sleep quality, focusing, and rumination than male controls (see Figure 1 for self-confidence), whereas female athletes and female controls did not differ from one another in these respects. In other words, male controls had the lowest (“poorest”) scores on the aforementioned dimensions. Taken together, no clear gender-related pattern of sleep and psychological functioning emerged. Insofar as gender-related differences emerged, these generally reflected lower scores of male controls. Determinants of sleep quality: Multiple regression analyses To predict sleep quality, tiredness and concentration during the day as a function of group, gender, psychological functioning, and level of exercise, three multiple regression analyses with a stepwise exclusion procedure were performed (Table 4). First, Durbin-Watson coefficients to indicate independence of residuals were satisfactory (Table 4). Second, after stepwise inclusion, multiple regression models sufficiently explained (R and R2) the dependent variables. | 1 Note that increased scores of tiredness imply low tiredness. Durbin-Watson-statistics coefficients between 1.5 and 2.5 indicate that the residuals of independent variables are independent. |
Results showed that the sleep quality was predicted by being an athlete and increased physical arousal but by lower stress, state anxiety, and rumination. Tiredness during the day was predicted by being a participant in the control group, increased stress, increased mental arousal, and an unfavorable attitude toward life. Concentration during the day was predicted by being an athlete, low trait anxiety, and low stress, but also by greater self-confidence, aggressive behavior, mental arousal, and decreased rumination. To sum, being an athlete and experiencing low stress were of value in predicting high sleep quality, low tiredness, and high concentration, whereas, for instance, depressive symptoms, gender, and total hours of vigorous exercising per week had no predictive value. Discussion The key findings of the present study are that adolescent athletes reported better sleep patterns and better psychological functioning than controls, and that adolescent male low exercisers were at increased risk for poor sleep and psychological functioning. Three hypotheses were formulated and will now be considered in turn. With the first hypothesis, we expected favorable sleep patterns among adolescent athletes compared with adolescent controls. Results confirmed this expectation, thus replicating an association previously reported for adults [13], [15], [17]. Most importantly, multiple regression analyses (Table 4) showed that independently from the influence of other predictor variables such as gender, level of exercise, or many variables related to psychological functioning, being an athlete predicted high sleep quality, low tiredness, and high concentration during the day. The reason why other studies failed to find a favorable association between physical exercise and sleep [14], [15] remains unclear, although the differences between studies could be caused by heterogeneity of samples as well as methodology (e.g., objective vs. subjective assessment of sleep and physical activity). A question does arise as to why intense exercising may be positively related to sleep. Polysomnographic sleep assessment of vigorous exercisers has shown increased slow wave sleep, reduced light sleep, and shortened SOL [21], [23], suggesting that exercise may benefit homeostatic sleep regulation. Although this might have been the case for the athletes assessed in the present study, other explanations are possible. First, vigorous exercise could have improved sleep indirectly via improved general psychological functioning [16], [17]. Second, athletes' sleep may have improved because of a more structured wake/sleep pattern, which normally promotes healthy sleep [2], [30]. In addition, both parental control and performance-related social support (e.g., trainers, physicians, psychologists) might contribute to a more structured life, very likely including sleep patterns. Finally, many athletes are well aware that getting rest and, consequently, good sleep, are important to recover from high-performance training and to avoid muscular injuries or mental burnout. With the second hypothesis, we predicted better psychological functioning in adolescent athletes compared with controls. The hypothesis was confirmed: athletes had lower scores for depressive symptoms and trait anxiety, and more favorable sleep-related personality traits. These findings corroborate a wealth of studies pointing to a favorable impact of regular exercise on psychological functioning among adults [16], [17], [19], [20]. Because of the cross-sectional design, however, we cannot rule out alternative directions of influence. For example, favorable personality traits might make adolescents more likely to engage in the kind of strenuous, long-term exercising that was characteristic of our athletes. Of note, and contrary to lay opinion, female athletes did not report higher levels of self-confidence. Thus female adolescents' self-confidence might depend more on other factors such as mothers' parenting styles [35]. Moreover, self-confidence is a multi-faceted construct [36], and high self-confidence with respect to a particular sport might not imply generalized self-confidence [18]. The third hypothesis anticipated poorer sleep patterns among females compared with males [6], [7]. However, our data did not confirm this prediction. Although gender × group interactions showed that female athletes did not differ from female controls, male controls reported the poorest sleep patterns. These results suggest that males taking less exercise may be at particular risk for poor sleep. Sleep duration, irrespective of group and gender, ranged from about 7 to about 9hours. Although this is less than the 9–10hours required according to Mercer et al [1], the observed range of sleeping duration is associated with good mental health according to Kaneita et al [8]. This observation might also explain why the effect sizes were generally small. In addition to the study limitations already mentioned, we add that participants were exclusively recruited from high schools and from high-school classes for skilled athletes, and only data of adolescents who voluntarily completed the questionnaires and the daily sleep logs were analyzed. Furthermore, one might object that no objective activity or sleep data were collected. However, there is evidence that subjective sleep data from sleep logs fit well with sleep-electroencephalography recordings [23]. Finally, the cross-sectional design of the study precludes conclusions about the direction of influence among sleep, psychological functioning, and personality traits (including motivation and volition). In conclusion, along with only two other studies [22], [23], the present data show that engaging in high amounts of exercise is positively related to favorable sleep patterns and psychological functioning in adolescents. These results provide grounds for promoting ready access to sports activities and for motivating adolescents to exercise regularly, especially male adolescents reporting little exercise behavior. Acknowledgments We thank Sandra Meier, Myrjam Jenny, Raphael Schär, Michael Wirth, and Martin Walde for data collection and data entry. We also thank the young people who participated in this study. Finally, we thank Nick Emler (Surrey, UK) for proofreading the manuscript. References [1]. [1]Mercer PW, Merritt SL, Cowell JM. Differences in reported sleep need among adolescents. J Adolesc Health. 1998;23:259–263.
CrossRef
[2]. [2]Moore M, Meltzer LJ. The sleepy adolescent: Causes and consequences of sleepiness in teens. Paediatr Respir Rev. 2008;9:114–120. Abstract | Full Text |
Full-Text PDF (207 KB)
[3]. [3]Millman RPWorking Group on Sleepiness in Adolescents/Young Adults; and AAP Committee on Adolescence. Excessive sleepiness in adolescents and young adults: Causes, consequences, and treatment strategies. Pediatrics. 2005;115:1774–1786. [4]. [4]Dahl RE, Lewin DS. Pathways to adolescent health sleep regulation and behavior. J Adolesc Health. 2002;31:175–184.
CrossRef
[5]. [5]Ohayon MM, Roberts RE, Zulley J, et al. Prevalence and sleep patterns of problematic sleep among older adolescents. J Am Acad Child Adolesc Psychiatry. 2000;39:1549–1556. Abstract | Full Text |
Full-Text PDF (129 KB)
|
CrossRef
[6]. [6]Moline ML, Broch L, Zak R, et al. Sleep in women across the life cycle from adulthood through menopause. Sleep Med Rev. 2003;7:155–177. Abstract |
Full-Text PDF (232 KB)
|
CrossRef
[7]. [7]Megdal SP, Schernhammer ES. Correlates for poor sleepers in a Los Angeles high school. Sleep Med. 2007;9:60–63. Abstract | Full Text |
Full-Text PDF (92 KB)
|
CrossRef
[8]. [8]Kaneita Y, Ohida T, Osaki Y, et al.Association between mental health status and sleep status among adolescents in Japan A nationwide cross-sectional survey. J Clin Psychiatry. 2007;68:1426–1435.
CrossRef
[9]. [9]Roberts RE, Roberts CR, Duong HT. Chronic insomnia and its negative consequences for health and functioning of adolescents: A 12-month prospective study. J Adolesc Health. 2008;42:294–302.
CrossRef
[10]. [10]Banks S, Dinges DF. Behavioral and physiological consequences of sleep restriction. J Clin Sleep Med. 2007;3:519–528. [11]. [11]Curcio G, Ferrara M, De Gennaro L. Sleep loss, learning capacity and academic performance. Sleep Med Rev. 2006;10:323–337. Abstract | Full Text |
Full-Text PDF (208 KB)
|
CrossRef
[12]. [12]American Academy of Sleep Medicine, ed. Sleep hygiene. Chicago, American Academy of Sleep Medicine, 2004. [13]. [13]Vuori I, Urponen H, Hasan J, et al. Epidemiology of exercise effects on sleep. Acta Physiol Scand. 1988;574(Suppl):3–7. [14]. [14]Driver HS, Taylor SR. Exercise and sleep. Sleep Med Rev. 2000;4:387–402. Abstract |
Full-Text PDF (141 KB)
|
CrossRef
[15]. [15]Youngstedt SD, Freelove-Charton JD. Exercise and sleep. In: Faulkner GEJ, Taylor AH editor. Exercise, Health and Mental Health. Emerging Relationships. London: Routledge; 2005;p. 159–189. [16]. [16]Dunn AL, Trivedi MH, Kampert JB, et al. Exercise treatment for depression: Efficacy and dose response. Am J Prev Med. 2005;28:1–8. Abstract | Full Text |
Full-Text PDF (236 KB)
|
CrossRef
[17]. [17]Youngstedt SD. Effects of exercise on sleep. Clin Sports Med. 2005;24:355–365. Abstract | Full Text |
Full-Text PDF (205 KB)
|
CrossRef
[18]. [18]Stein C, Fisher L, Berkey C, et al. Adolescent physical activity and perceived competence: Does change in activity level impact self-perception?. J Adolesc Health. 2007;40:462;. [19]. [19]In: Biddle SJ, Mutrie N editor. Psychology of Physical Activity. London: Routledge; 2008;. [20]. [20]In: Faulkner GEJ, Taylor AH editor. Exercise, Health and Mental Health. Emerging Relationships. London: Routledge; 2005;. [21]. [21]Dworak M, Wiater A, Alfer D, et al. Increased slow wave sleep and reduced stage 2 sleep in children depending on exercise intensity. Sleep Med. 2008;9:266–272. Abstract | Full Text |
Full-Text PDF (205 KB)
|
CrossRef
[22]. [22]Tynjälä J, Kannas L, Levälahti E, et al. Perceived sleep quality and its precursors in adolescents. Health Promot Int. 1999;14:155–166.
CrossRef
[23]. [23]Brand S, Beck J, Gerber M, et al. Evidence of favorable sleep-EEG patterns in adolescent male vigorous football players compared with controls. World J Biol Psychiatry. 2009;. [24]. [24]Liu X, BuyesseSleep DJ. Youth suicidal behavior: A neglected field. Curr Opin Psychiatry. 2005;19:288–293. MEDLINE [25]. [25]Hyde JS, Mezulis AH, Abramson LY. The ABCs of depression: Integrating affective, biological, and cognitive models to explain the emergence of the gender difference in depression. Psychol Rev. 2008;115:291–313.
CrossRef
[26]. [26]Iannotti RJ, Kogan MD, Janssen I, et al. Patterns of adolescent physical activity, screen-based media use, and positive and negative health indicators in the U.S. and Canada. J Adolesc Health. 2009;44:493–499.
CrossRef
[27]. [27]Friedman HS, Martin LR, Tucker JS, et al. Stability of physical activity across the lifespan. J Health Psychol. 2008;13:1092–1104.
CrossRef
[28]. [28]Pfeiffer K, Dowda M, Dishman RK, et al. Sport participation and physical activity in adolescent females across a four-year period. JAdolesc Health. 2006;39:523–529. [29]. [29]Buysse DJ, Reynolds CF, Monk TH, et al. The Pittsburgh Sleep Quality Index: New instrument for psychiatric practice and research. Psychiatry Rev. 1989;28:193–213. [30]. [30]In: Backhaus J, Riemann D editor. Schlafstörungen bewältigen [Coping with sleeping disorders]. Weinheim: Beltz Psychologie Verlags Union; 1996;. [31]. [31]In: von Zerssen D editors. Depressivitäts-Skala [Depression Scale]. Göttingen: Hogrefe; 1976;. [32]. [32]In: Laux L, Glanzmann P, Schaffner P editor. State-Trait-Angstinventar [German version of Spielberger, et al.'s State-Trait-Anxiety Inventory]. Göttingen: Hogrefe; 1981;. [33]. [33]In: Hoffmann RM, Rasch T, Schnieder G editor. Fragebogen zur Erfassung allgemeiner Persönlichkeitsmerkmale Schlafgestörter (FEPS-I and II) [Questionnaire for assessing general personality traits of patients suffering from sleep disorders]. Göttingen: Hogrefe; 1996;. [34]. [34]Brand S, Hatzinger M, Beck J, et al. Perceived parenting style, personality traits, and sleep patterns in adolescents. J Adolesc. 2009;. [35]. [35]Heaven PC, Ciarrochi J. Parental styles, conscientiousness, and academic performance in high school: A three-wave longitudinal study. Pers Soc Psychol Bull. 2008;34:451–461.
CrossRef
[36]. [36]Shavelson RJ, Hubner JJ, Stanton GC. Self-concept: Validation of construct interpretations. Rev Educ Res. 1976;46:407–441. a Psychiatric Hospital of the University of Basel, Depression and Sleep Research Unit, Basel, Switzerland b Institute of Exercise and Health Sciences, University of Basel, Basel, Switzerland c Psychiatric Out-Patient Clinic of the University of Basel, Basel, Switzerland  Address correspondence to: Serge Brand, Ph.D., Psychiatric Hospital of the University of Basel, Depression and Sleep Research Unit, Wilhelm Klein-Strasse 27, 4025 Basel, Switzerland.
PII: S1054-139X(09)00255-9 doi:10.1016/j.jadohealth.2009.06.018 © 2010 Society for Adolescent Medicine. Published by Elsevier Inc. All rights reserved. | |
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