Social jetlag refers to the chronic shift in sleep timing between work and free days and has been associated with a variety of negative physical and psychological outcomes. Existing research on social jetlag has relied heavily on cross-sectional studies, preventing researchers and practitioners from assessing the effects of social jetlag over time. The current study used longitudinal data to explore the directionality of the association between social jetlag and depressive symptoms as well as the longitudinal associations between social jetlag, academic performance, and wellbeing in college students. Gender and race were also assessed as potential moderators of these associations. Cross-lagged panel analysis using Amos for SPSS revealed that social jetlag predicted depressive symptoms both concurrently adjusting for covariates and longitudinally in unadjusted models. This finding suggests that sleep disturbances may precede mood concerns, although causality cannot be proven due to the design of the current study. PROCESS moderation analyses indicated that social jetlag did not significantly predict academic performance or wellbeing over time, and neither gender nor race moderated these associations. Future research is needed to further assess the short- and long-term outcomes of social jetlag using prospective, well-controlled studies and objective measures of sleep timing.

This diploma thesis focuses of czech population's description from the perspective of chronotype and its relationship to sociodemographic characteristics and to variables affecting lifestyle. The aim of this thesis is to describe the sample examined in terms of social jetlag. The thesis is based mainly on quantitative methods, specifically I was using individual forms of regression analyzes, which allow to capture the influence of independent variables on the dependent variable. The analytical part data from Qualitas 2016 survey within the AV21 Strategy project are processed. The analysis revealed the existence of an association between chronotype and gender, respectively between chronotype and age. It also turned out that extreme owls consume addictive substances to a greater extent than extreme larks. Owls also generally have higher BMI, lower psychological well-being and more often suffer from social jetlag than those with early circadian preference. However, the social jetlag does not only concern respondents with late circadian preference, but the whole sample analyzed. The average length of social jetlag in the sample is 66 minutes. The analysis also revealed the link between social jetlag and addictive substance abuse.

According to recent nationwide surveys there have been dramatic increases in stress and serious stress-related health problems among Swedish adolescents. The aims of the present thesis were to investigate the prevalence of perceived chronic stress among sixteen-year-old adolescents who attended their first year at high-ranking high schools in the Stockholm area, to examine if factors that have been found to be relevant in the development of chronic stress among adults also contribute to chronic stress among adolescents, and to investigate the associations between chronic stress and sleep-related variables and academic achievement. Data were collected by means of self-report instruments. The main outcomes showed that a substantial number of individuals (30%) reported to perceive severe stress symptoms. The highest degree was perceived by 8% who suffered from symptoms to an extent which otherwise only has been observed among adult clinical burnout patients. Besides, 15% reported severe stress symptoms throughout high school and were thus considered to suffer from chronic stress. Perceived high demands, low global self-esteem, sleep disturbances and low social support were crucial factors in explaining stress symptoms. Another finding showed that perceived chronic stress was associated with adolescents’ academic achievement. A closer look at the potential contribution of sleep-related variables to academic achievement revealed further that, apart from severe stress symptoms, social jetlag was involved in predicting variation in academic achievement. Overall, the findings indicated that there is a high prevalence of chronic stress among adolescents. The results should be taken seriously, as young people’s sense of well-being during this period impacts both their successful transition into adulthood and their life course. Future research options and potential practical applications in terms of chronic stress prevention were suggested and discussed. / <p>At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 3: Submitted.</p>

As preferências interindividuais de fase circadiana também são denominadas de cronotipo, considerado como um traço pessoal e caracterizado pelas diferenças dos ritmos circadianos. Nos últimos anos o interesse no estudo desta tipologia tem aumentado, sendo de particular relevância para compreender a organização temporal do processo de regulação do organismo. O questionário de Cronotipo de Munique (MCTQ) é um novo método de avaliação do cronotipo que avalia o período médio do sono durante os dias livres e de trabalho. As características individuais cronobiológicas, relacionadas às preferências para alocar as atividades durante o dia, também foram relacionadas aos distúrbios de humor. O presente trabalho foi realizado pelo núcleo de pesquisa de Cronobiologia do Hospital de Clínicas em colaboração coma a Universidade de Munique na Alemanha, tendo por objetivo avaliar em uma amostra populacional do Vale do Taquari a variabilidade interindividual dos cronotipos e sua relação com os níveis de sintomas depressivos. Foi observada uma dependência entre as variáveis de idade e gênero tanto para a distribuição do MCTQ, quanto para a distribuição dos escores da BECK. A distribuição do BECK mostrou uma correlação não linear com o MSF (Pearson = 0,094; p < 0,0001), demonstrando que os sintomas depressivos predominaram na maior parte entre os indivíduos que apresentam um avanço na fase do sono, mas também os tipos matutinos apresentaram uma tendência de maior pontuação na escala BECK. Houve uma diferença no ponto médio do sono entre dias de trabalho e os dias livres, nos diferentes cronotipos. Essa característica foi denominada no presente estudo como jet lag social e mostrou uma correlação positiva tanto com MSF (Spearman r2 = 0,381, p < 0,0001), quanto com BECK (Spearman r2 = 0,297, p < 0,0001). Quanto maior o jet lag social, mais intenso foram os sintomas depressivos, os indivíduos que apresentaram jet lag social entre 0 e 2 horas (N = 3.674) relataram sintomas significativamente menores de depressão do que aqueles que apresentaram 2 a 4 horas (N = 320), ou mais de 4 horas (N = 57, ANOVA: F = 79,36, p < 0,0001). A correlação entre o nível de sintomas depressivos e o jet lag social não ocorreu somente nos grupos vespertinos, mas também entre os tipos intermediários e matutinos (Spearman r2 = 0,233, p < 0,0001; r2 = 0,275, p = 0,0001 e r2 = 0,311, p < 0,0001, respectivamente). Estes resultados sugerem que a relação do cronotipo com o risco de sintomas depressivos pode ser entendida pela exposição destes indivíduos a situações de periodicidade ambiental diferentes da ritmicidade interna do organismo, o que corresponde a um desalinhamento dos ritmos circadianos internos com os externos. / The individual circadian phase preferences, also called chronotype, are an attribute of human beings, which is characterized by differences in circadian rhythms. The interest in the study of individual typology differences has increased in the last years. It is also relevant for understanding the temporal organization of the body’s regulatory process. The Munich Chronotype Questionnaire (MCTQ) is a new method developed to assess chronotype based on individual midsleep phase. Individual chronobiology characteristics to allocate activities during the day were also related to mood disorders. This work was carried out by the research group of Chronobiology at Clinicas Hospital in collaboration with the University of Munich in Germany. The objective of this study was to evaluate the interindividual variability of chronotypes and its correlation to the levels of depressive symptoms in a sample of rural population in Vale Taquari. As a result, we observed a dependence between the variables of age and gender distribution of both MCTQ and Beck scores. The distribution of Beck showed a nonlinear correlation with MSF (Pearson = 0.094, p <0.0001), demonstrating that depressive symptoms were prevalent mostly among people who have a sleep phase advance, but also the morning types showed a trend of higher scores on the Beck scale (ANOVA: F = 23:14, p <0.0001). The difference in the midpoint of sleep between workdays and free days was dependent on chronotypes. In this study that was called social jet lag and showed a positive correlation with both MSF (Spearman r2 = 0.381, p <0.0001) and BECK (Spearman r2 = 0.297, p <0.0001). The level of social jet lag was correlated to depressive symptoms. Individuals who had a social jet lag from 0 to 2 hours (N = 3,674) reported significantly less symptoms of depression than those which reported to 2 to 4 hours (N = 320), or more than 4 hours (N = 57, ANOVA: F = 79.36, p <0.0001). The correlation between the level of depressive symptoms and social jet lag did not occur only in the late type, but also between the morning and intermediate types (Spearman r2 = 0.233, p <0.0001, r2 = 0.275, p = 0.0001 and r2 = 0.311, p <0.0001, respectively). These results suggest that the relationship between chronotypes with the risk of depressive symptoms can be understood through the exposure of these individuals to environmental differences in the body's internal rhythm frequency. Additionally it can be suggesting that these changes also correspond to a misalignment of circadian rhythms with internal and external rhythm.

As preferências interindividuais de fase circadiana também são denominadas de cronotipo, considerado como um traço pessoal e caracterizado pelas diferenças dos ritmos circadianos. Nos últimos anos o interesse no estudo desta tipologia tem aumentado, sendo de particular relevância para compreender a organização temporal do processo de regulação do organismo. O questionário de Cronotipo de Munique (MCTQ) é um novo método de avaliação do cronotipo que avalia o período médio do sono durante os dias livres e de trabalho. As características individuais cronobiológicas, relacionadas às preferências para alocar as atividades durante o dia, também foram relacionadas aos distúrbios de humor. O presente trabalho foi realizado pelo núcleo de pesquisa de Cronobiologia do Hospital de Clínicas em colaboração coma a Universidade de Munique na Alemanha, tendo por objetivo avaliar em uma amostra populacional do Vale do Taquari a variabilidade interindividual dos cronotipos e sua relação com os níveis de sintomas depressivos. Foi observada uma dependência entre as variáveis de idade e gênero tanto para a distribuição do MCTQ, quanto para a distribuição dos escores da BECK. A distribuição do BECK mostrou uma correlação não linear com o MSF (Pearson = 0,094; p < 0,0001), demonstrando que os sintomas depressivos predominaram na maior parte entre os indivíduos que apresentam um avanço na fase do sono, mas também os tipos matutinos apresentaram uma tendência de maior pontuação na escala BECK. Houve uma diferença no ponto médio do sono entre dias de trabalho e os dias livres, nos diferentes cronotipos. Essa característica foi denominada no presente estudo como jet lag social e mostrou uma correlação positiva tanto com MSF (Spearman r2 = 0,381, p < 0,0001), quanto com BECK (Spearman r2 = 0,297, p < 0,0001). Quanto maior o jet lag social, mais intenso foram os sintomas depressivos, os indivíduos que apresentaram jet lag social entre 0 e 2 horas (N = 3.674) relataram sintomas significativamente menores de depressão do que aqueles que apresentaram 2 a 4 horas (N = 320), ou mais de 4 horas (N = 57, ANOVA: F = 79,36, p < 0,0001). A correlação entre o nível de sintomas depressivos e o jet lag social não ocorreu somente nos grupos vespertinos, mas também entre os tipos intermediários e matutinos (Spearman r2 = 0,233, p < 0,0001; r2 = 0,275, p = 0,0001 e r2 = 0,311, p < 0,0001, respectivamente). Estes resultados sugerem que a relação do cronotipo com o risco de sintomas depressivos pode ser entendida pela exposição destes indivíduos a situações de periodicidade ambiental diferentes da ritmicidade interna do organismo, o que corresponde a um desalinhamento dos ritmos circadianos internos com os externos. / The individual circadian phase preferences, also called chronotype, are an attribute of human beings, which is characterized by differences in circadian rhythms. The interest in the study of individual typology differences has increased in the last years. It is also relevant for understanding the temporal organization of the body’s regulatory process. The Munich Chronotype Questionnaire (MCTQ) is a new method developed to assess chronotype based on individual midsleep phase. Individual chronobiology characteristics to allocate activities during the day were also related to mood disorders. This work was carried out by the research group of Chronobiology at Clinicas Hospital in collaboration with the University of Munich in Germany. The objective of this study was to evaluate the interindividual variability of chronotypes and its correlation to the levels of depressive symptoms in a sample of rural population in Vale Taquari. As a result, we observed a dependence between the variables of age and gender distribution of both MCTQ and Beck scores. The distribution of Beck showed a nonlinear correlation with MSF (Pearson = 0.094, p <0.0001), demonstrating that depressive symptoms were prevalent mostly among people who have a sleep phase advance, but also the morning types showed a trend of higher scores on the Beck scale (ANOVA: F = 23:14, p <0.0001). The difference in the midpoint of sleep between workdays and free days was dependent on chronotypes. In this study that was called social jet lag and showed a positive correlation with both MSF (Spearman r2 = 0.381, p <0.0001) and BECK (Spearman r2 = 0.297, p <0.0001). The level of social jet lag was correlated to depressive symptoms. Individuals who had a social jet lag from 0 to 2 hours (N = 3,674) reported significantly less symptoms of depression than those which reported to 2 to 4 hours (N = 320), or more than 4 hours (N = 57, ANOVA: F = 79.36, p <0.0001). The correlation between the level of depressive symptoms and social jet lag did not occur only in the late type, but also between the morning and intermediate types (Spearman r2 = 0.233, p <0.0001, r2 = 0.275, p = 0.0001 and r2 = 0.311, p <0.0001, respectively). These results suggest that the relationship between chronotypes with the risk of depressive symptoms can be understood through the exposure of these individuals to environmental differences in the body's internal rhythm frequency. Additionally it can be suggesting that these changes also correspond to a misalignment of circadian rhythms with internal and external rhythm.

As preferências interindividuais de fase circadiana também são denominadas de cronotipo, considerado como um traço pessoal e caracterizado pelas diferenças dos ritmos circadianos. Nos últimos anos o interesse no estudo desta tipologia tem aumentado, sendo de particular relevância para compreender a organização temporal do processo de regulação do organismo. O questionário de Cronotipo de Munique (MCTQ) é um novo método de avaliação do cronotipo que avalia o período médio do sono durante os dias livres e de trabalho. As características individuais cronobiológicas, relacionadas às preferências para alocar as atividades durante o dia, também foram relacionadas aos distúrbios de humor. O presente trabalho foi realizado pelo núcleo de pesquisa de Cronobiologia do Hospital de Clínicas em colaboração coma a Universidade de Munique na Alemanha, tendo por objetivo avaliar em uma amostra populacional do Vale do Taquari a variabilidade interindividual dos cronotipos e sua relação com os níveis de sintomas depressivos. Foi observada uma dependência entre as variáveis de idade e gênero tanto para a distribuição do MCTQ, quanto para a distribuição dos escores da BECK. A distribuição do BECK mostrou uma correlação não linear com o MSF (Pearson = 0,094; p < 0,0001), demonstrando que os sintomas depressivos predominaram na maior parte entre os indivíduos que apresentam um avanço na fase do sono, mas também os tipos matutinos apresentaram uma tendência de maior pontuação na escala BECK. Houve uma diferença no ponto médio do sono entre dias de trabalho e os dias livres, nos diferentes cronotipos. Essa característica foi denominada no presente estudo como jet lag social e mostrou uma correlação positiva tanto com MSF (Spearman r2 = 0,381, p < 0,0001), quanto com BECK (Spearman r2 = 0,297, p < 0,0001). Quanto maior o jet lag social, mais intenso foram os sintomas depressivos, os indivíduos que apresentaram jet lag social entre 0 e 2 horas (N = 3.674) relataram sintomas significativamente menores de depressão do que aqueles que apresentaram 2 a 4 horas (N = 320), ou mais de 4 horas (N = 57, ANOVA: F = 79,36, p < 0,0001). A correlação entre o nível de sintomas depressivos e o jet lag social não ocorreu somente nos grupos vespertinos, mas também entre os tipos intermediários e matutinos (Spearman r2 = 0,233, p < 0,0001; r2 = 0,275, p = 0,0001 e r2 = 0,311, p < 0,0001, respectivamente). Estes resultados sugerem que a relação do cronotipo com o risco de sintomas depressivos pode ser entendida pela exposição destes indivíduos a situações de periodicidade ambiental diferentes da ritmicidade interna do organismo, o que corresponde a um desalinhamento dos ritmos circadianos internos com os externos. / The individual circadian phase preferences, also called chronotype, are an attribute of human beings, which is characterized by differences in circadian rhythms. The interest in the study of individual typology differences has increased in the last years. It is also relevant for understanding the temporal organization of the body’s regulatory process. The Munich Chronotype Questionnaire (MCTQ) is a new method developed to assess chronotype based on individual midsleep phase. Individual chronobiology characteristics to allocate activities during the day were also related to mood disorders. This work was carried out by the research group of Chronobiology at Clinicas Hospital in collaboration with the University of Munich in Germany. The objective of this study was to evaluate the interindividual variability of chronotypes and its correlation to the levels of depressive symptoms in a sample of rural population in Vale Taquari. As a result, we observed a dependence between the variables of age and gender distribution of both MCTQ and Beck scores. The distribution of Beck showed a nonlinear correlation with MSF (Pearson = 0.094, p <0.0001), demonstrating that depressive symptoms were prevalent mostly among people who have a sleep phase advance, but also the morning types showed a trend of higher scores on the Beck scale (ANOVA: F = 23:14, p <0.0001). The difference in the midpoint of sleep between workdays and free days was dependent on chronotypes. In this study that was called social jet lag and showed a positive correlation with both MSF (Spearman r2 = 0.381, p <0.0001) and BECK (Spearman r2 = 0.297, p <0.0001). The level of social jet lag was correlated to depressive symptoms. Individuals who had a social jet lag from 0 to 2 hours (N = 3,674) reported significantly less symptoms of depression than those which reported to 2 to 4 hours (N = 320), or more than 4 hours (N = 57, ANOVA: F = 79.36, p <0.0001). The correlation between the level of depressive symptoms and social jet lag did not occur only in the late type, but also between the morning and intermediate types (Spearman r2 = 0.233, p <0.0001, r2 = 0.275, p = 0.0001 and r2 = 0.311, p <0.0001, respectively). These results suggest that the relationship between chronotypes with the risk of depressive symptoms can be understood through the exposure of these individuals to environmental differences in the body's internal rhythm frequency. Additionally it can be suggesting that these changes also correspond to a misalignment of circadian rhythms with internal and external rhythm.

博士(スポーツ健康科学) / Doctor of Philosophy in Health and Sports Science / 同志社大学 / Doshisha University

Thèse de doctorat présenté en vue de l'obtention du doctorat en psychologie - recherche intervention, option neuropsychologie clinique (Ph.D) / L’enfant doué connait un rythme de développement distinct entre les sphères intellectuelle, affective et relationnelle de son développement. Bon nombre d’enfants doués se sentent différents et incompris en raison de leur profil de développement asynchrone. Il en découle des difficultés d’adaptation, des manifestations de souffrance psychologique, des difficultés académiques de même que des erreurs diagnostiques (Lançon et al., 2015; Terrassier et Gouillou, 2016; Vaivre-Douret, 2011). Afin d’optimiser les chances que les enfants doués développent leur plein potentiel et puissent jouir d’une bonne santé mentale, il est essentiel de mieux comprendre leurs différences et les facteurs qui rendent ces enfants à risque de problèmes sociaux, émotionnels et comportementaux. Un sommeil de qualité est essentiel pour un développement harmonieux et un fonctionnement diurne adapté (Gregory et Sadeh, 2012; Matricciani et al., 2019). Pourtant, aucune étude n’a à ce jour tracé un portrait détaillé des caractéristiques du sommeil des enfants doués ou étudié les liens entre d’éventuelles difficultés de sommeil chez ces enfants et les problèmes émotionnels et comportementaux qui nuisent au développement de leur plein potentiel. Or, une meilleure compréhension de leur profil de sommeil permettrait potentiellement d’expliquer et de comprendre les comportements inadaptés chez cette population. La présente thèse avait donc pour objectif d’étudier le profil de sommeil des enfants doués à l’aide de mesures subjectives et objectives, de le comparer à celui d’enfants au développement typique, puis d’analyser dans les deux groupes les liens entre les caractéristiques du sommeil et le fonctionnement diurne. La première étude visait à évaluer, par l’entremise de questionnaires remplis par les parents, la présence de difficultés de sommeil et de problèmes émotionnels et comportementaux dans un échantillon d’enfants doués et à explorer le rôle des problèmes de sommeil dans la relation entre la douance et les comportements intériorisés et extériorisés. Les résultats ont montré qu’être doué augmentait de 4,67 fois le risque d'avoir des problèmes de sommeil et de 14,12 fois le risque d'avoir des comportements inadaptés. Également, les problèmes de sommeil avaient tendance à modérer la relation entre la douance et les difficultés d'adaptation de sorte que la combinaison douance et problèmes de sommeil s’avérait être particulièrement préjudiciable au fonctionnement socioémotionnel et comportemental. La deuxième étude visait à examiner sur plusieurs nuits de façon objective par actigraphie la durée, la qualité et la variabilité intra-individuelle du sommeil des enfants doués de même que les plaintes parentales liées au sommeil de leur enfant. Les résultats de cette étude ont montré que les enfants doués présentaient une efficacité de sommeil moindre, caractérisée par des difficultés à maintenir le sommeil, et plus de variabilité intra-individuelle que les enfants au développement typique. Par ailleurs, les enfants doués montraient moins de décalage horaire social par rapport aux enfants du groupe contrôle. Enfin, les parents des enfants doués rapportaient significativement plus de plaintes liées au sommeil de leur enfant que les parents des enfants du groupe d’appariement. La troisième étude visait à évaluer objectivement par polysomnographie la macrostructure du sommeil et divers indicateurs de stabilité du sommeil – c.-à-d., éveils nocturnes, microéveils et transitions entre les stades de sommeil – chez les enfants doués puis à analyser les liens entre la physiologie de leur sommeil et leurs comportements inadaptés. Les résultats ont démontré que les enfants doués avaient significativement plus de stade N1 et moins de stade N3 comparativement aux enfants au développement typique. Chez les enfants doués, plus de stade N1 était corrélé à plus de problèmes extériorisés et moins de stade N3 était corrélé à plus de problèmes intériorisés. Les enfants doués avaient également plus de SP, qui n'était pas significativement associé aux échelles comportementales. Enfin, les enfants doués présentaient deux tendances opposées d'instabilité du sommeil : 1) plus d'instabilité impliquant le stade N1 et 2) moins d'instabilité impliquant les stades N2, N3 et le SP. La stabilité du sommeil – c.-à-d., moins de transition entre les stades du sommeil – était plus élevée chez les enfants doués que chez les enfants du groupe contrôle, et associée à moins de comportements indésirables. En somme, ces trois études ont permis de dresser un portrait beaucoup plus précis du sommeil et des caractéristiques émotionnelles et comportementales des enfants doués. Ensemble, ces recherches ont permis de déterminer que les enfants doués sont une population à risque de problèmes de sommeil et que le sommeil constitue un facteur sur lequel agir afin de favoriser un développement harmonieux chez les enfants doués et améliorer leur bien-être. / Giftedness is characterized by an intellectual development superior to peers while emotional and relational development corresponds to the age norms. Because of their asynchronous development profile, many gifted children feel different and misunderstood. This results in psychological problems, relationship difficulties, academic difficulties as well as frequent misdiagnoses (Lançon et al., 2015; Terrassier & Gouillou, 2016; Vaivre-Douret, 2011). Hence, to maximize the chances that gifted children develop their full potential and benefit from good psychological health, it is essential to better understand their differences and factors that make these children at risk of social, emotional, and behavioral problems. Sleep is essential for healthy development and optimal daytime functioning (Gregory & Sadeh, 2012; Matricciani et al., 2019). However, no study has yet drawn an accurate picture of gifted children’s sleep characteristics or investigated the relation between gifted children's sleep and their socio-emotional functioning. A better understanding of gifted children’s sleep characteristics could help explain their maladaptive behaviors. Accordingly, the objective of this thesis was to study the sleep profile of gifted children using subjective and objective measures, to compare it with that of typically-developing children and to analyze the links between sleep characteristics and daytime functioning in these two groups. The first study aimed to investigate with questionnaires completed by parents the risk of sleep and emotional problems in gifted children and to explore the role of sleep problems in the relation between giftedness and internalized and externalized behaviors. Results revealed that being in the gifted children group increased by 4.67 times the risk of having sleep problems and 14.12 times the risk of having maladaptive behaviors. Moreover, sleep problems tended to moderate the relation between giftedness and adjustment difficulties, such that the combination of giftedness and sleep problems appeared to be particularly prejudicial to socio-emotional functioning. The second study investigated habitual sleep, night-to-night sleep variability, and parental reports of sleep in gifted children using actigraphy. The clearest finding to emanate from this study is that gifted children have lower sleep efficiency, characterized by sleep maintenance problems, and more sleep intraindividual variability than typically-developing children. Additionally, we found gifted children to experience less social jetlag compared to typically-developing children. Gifted children also showed more clinically significant sleep problems as reported by their parents. The third study aimed to investigate sleep macrostructure and instability – i.e., awakenings, microarousal, and stage shifts – in gifted children in relation with problematic behaviors using polysomnography. We found significantly more stage N1 and less stage N3 in gifted children compared to typically-developing children. More stage N1 sleep was correlated with more externalizing problems and less stage N3 sleep was correlated with more internalizing problems. Gifted children also displayed more REM sleep, but this was not significantly correlated with behavioral scales. Gifted children displayed two opposing trends of sleep instability: more instability involving N1 sleep and less instability involving N2, N3 and REM sleep. Sleep stability – i.e., less stage shift – was higher in gifted children than in typically-developing children and associated with fewer unwanted behaviors. In conclusion, these three studies provided a much more accurate picture of sleep, emotional and behavioral characteristics of gifted children. Together, this research has made it possible to determine that gifted children are at risk for sleep problems and that sleep is a factor on which to act in order to promote harmonious development in gifted children and improve their well-being.

Au cours de la préadolescence, la durée totale de sommeil diminue et des retards importants dans l’horaire de sommeil se produisent. Cependant, la plupart des études utilisent des données transversales et/ou des mesures subjectives du sommeil, limitant la qualité méthodologique des données. Aussi, le point milieu du sommeil, le décalage horaire social (DHS) et la variabilité intra-individuelle (VII) du sommeil restent rarement abordés. Nous avons suivi 128 préadolescents (69 filles) ayant un développement typique pendant 4 ans, entre les âges de 8 et 12 ans. L’actigraphie a été utilisée pour déterminer le sommeil typique (soit la valeur moyenne), le DHS et la VII de quatre aspects du sommeil : l’heure du coucher, l’heure du lever, le point milieu du sommeil et la durée totale de sommeil. Des courbes de croissance multiniveaux ont été modélisées pour examiner à la fois les changements intra- et inter-individuels. Avec l'âge, l'horaire de sommeil devient progressivement plus tardif, la durée de sommeil diminue linéairement, et des augmentations significatives sont observés à la fois pour le DHS et la VII. Des différences individuelles autour des moyennes du groupe ont aussi été notées pour le DHS de l'heure du coucher et de la durée de sommeil. De plus, les filles présentent des différences plus importantes dans leur sommeil entre les jours comparativement aux garçons. Ces résultats décrivent des changements significatifs dans le sommeil des préadolescents au cours des années. Nous discutons des implications potentielles de ces trajectoires sur le fonctionnement physiologique, psychologique et social des jeunes. / Pre-adolescence is a period of marked changes in sleep-wake cycles characterized by a gradual decrease in adolescents' total sleep time (TST) and later sleep schedules with age. However, much of the research supporting these developmental trends has been based on cross-sectional data and/or subjective measures of sleep, limiting the methodological quality of the evidence. Additionally, important sleep parameters, like sleep midpoint, social jetlag and variability in sleep remain seldomly studied. We followed 128 typically developing preadolescents (69 female) over 4 years, between ages 8 and 12 years. Actigraphy-derived estimates of typical (i.e., mean) sleep, social jetlag and intra-individual variability were obtained for four sleep parameters: sleep onset, sleep offset, sleep midpoint, and TST. Multilevel growth curves were modelled to examine both within-person change and between-person differences in these trajectories. Across the period of pre-adolescence, sleep schedule became progressively later, mean TST decreased linearly, and significant increases were observed for both social jetlag and variability in sleep. Important individual differences around the average group estimates were noted for the social jetlag of sleep offset and TST. Sex differences were also observed, with girls experiencing greater between-day differences in their sleep than boys. These results describe significant age-related changes in the sleep of pre-adolescents. We discuss potential implications of these trajectories on youths’ physiological, psychological, and social functioning.