Morningness: protective factor for sleep-related and emotional problems in childhood and adolescence?

Social and circadian rhythm dysregulation and suicide: A systematic review and meta-analysis

This systematic review of 52 studies provides a quantitative synthesis of the empirical literature on social and circadian rhythm correlates of suicidal thoughts and behaviors (STB). Small-to-medium pooled effect sizes were observed for associations between evening chronotype and STB and suicidal ideation (SI), although the pooled effect size diminished when accounting for publication bias. Three studies employed longitudinal designs and suggested eveningness was predictive of future STB, with a small-to-medium effect size. Social rhythm irregularity was also a significant correlate of STB with pooled effect sizes in the medium range. Overall circadian rhythm disruption was not associated with STB, although certain circadian rhythm metrics, including mean daytime activity, circadian rhythm sleep-wake disorder diagnosis, and actigraphy-assessed amplitude were associated with STB. Pooled effect sizes for these indices were in the medium to large range. There is a need for additional longitudinal research on actigraphy-based circadian parameters and objective markers of circadian phase (i.e., dim-light melatonin onset) to gain a clearer understanding of associations of endogenous circadian function and STB beyond that which can be captured via self-report.

Can morning affect protect us from suicide? The mediating role of general mental health in the relationship between chronotype and suicidal behavior among students

Although chronotype has been associated with suicidal behavior, current research suggest that this relationship may be mediated by other factors. The aim of this study was to assess whether chronotype, specifically morningness, may predict suicidal behavior and whether this relationship may be mediated by general mental health, depressive and anxiety symptoms, and/or social functioning among young adults. The study group comprised 306 students: 204 (65.8%) women, 101 (32.6%) men and one who chose not to identify with either option (0.3%). The participants completed The Composite Scale of Morningness, The General Health Questionnaire, 30-item version, Suicide Acceptance Questionnaire and The Suicidal Behaviors Questionnaire-Revised. Correlations between the continuous variables of interest revealed a weak, but significant, negative association between morning affect (CSM) and suicidal behavior (SBQ-R); a moderate positive association was found between suicidal behavior (SBQ-R) and depression/anxiety, and a weak one between suicidal behavior (SBQ-R) and interpersonal relations (GHQ-30). The models predicting suicidal behavior, and chronotype-related variables as predictors of suicidal behavior, were then tested. Although the morning affect predicted suicidal behavior, this effect became irrelevant when combined with mental health characteristics: psychopathological symptoms of depression and anxiety and the quality of interpersonal relations. Our findings imply that the role of chronotype is secondary to general mental health: mental disorder symptoms should be considered as the core risk factors for suicide and serve as the focus for suicide risk assessments.

Associations between chronotype, sleep quality, maternal mental health, and child development in mother-infant dyads

OBJECTIVE/BACKGROUND

Studies on circadian rhythms throughout development and their physiological and behavioral impacts at early stages are still scarce. Previous studies have shown that mother-infant interactions are important for both sleep and child development. In this cross-sectional study we investigated whether infants' chronotype, sleep and development were associated with their respective mothers' chronotype, sleep, mental health and socioeconomic status.

PATIENTS/METHODS

the following were used to evaluate mothers: the Morningness-Eveningness Questionnaire (MEQ), Pittsburgh Sleep Quality Index (PSQI), Epworth Sleepiness Scale (ESS) and Self-Reporting Questionnaire 20 (SRQ-20). To assess the infants' characteristics, the following were used: the 19th question from the Morningness-Eveningness Questionnaire (MEQ), infant nocturnal midpoint of sleep (iMSF), Brief Infant Sleep Questionnaire (BISQ) and Ages and Stages Questionnaire-3 (ASQ3). Socioeconomic aspects were assessed using the Brazilian Economic Class Criterion of the Brazilian Association of Research Companies (ABEP).

RESULTS

A hundred and eight mother-infant dyads participated in the study. Sleep disorders were observed in 38 (35%) infants and atypical development (ASQ3) in 35 (32%). The infants' sleep phases were partially explained by the mother's chronotype. Infants' sleep duration was negatively correlated with sleep latency, which was higher in the group with atypical development. Mothers of infants with sleep disorders or discordant chronotypes (32%) had higher Pittsburgh scores (worse sleep quality) and higher SRQ-20 scores (screen for Common Mental Disorders).

CONCLUSIONS

We found evidence for the contribution of sleep quality and chronotypes to mothers' mental health and infant development. However, further studies are needed to confirm the influence of sleep and circadian phenotypes in the early stages.

Evaluation of sleep habits, sleep chronotype, and quality of life in children with drug-resistant epilepsy in Turkey

BACKGROUND/AIM

Drug-resistant epilepsy (DRE) is a condition that affects sleep habits and the quality of life of children unfavorably. The aim of our study was to evaluate the relationship of sleep habits and sleep chronotype with the quality of life and behavioral problems in children with DRE.

MATERIALS AND METHODS

In our study, 2-11-year-old children, who were either healthy or diagnosed with DRE, were evaluated. A sociodemographic data form was filled out to evaluate the general characteristics of children. The Children's Sleep Habits Questionnaire (CSHQ) and the Children's Chronotype Questionnaire (CCTQ) for sleep habits, the Pediatric Quality of Life Inventory (PedsQL) for the quality of life, and the Aberrant Behavior Checklist (ABC) for behavioral problems were filled out through face-to-face interviews with parents.

RESULTS

Thirty children with DRE and 31 healthy children were included in our study. Statistically significant differences were found in children with DRE compared to the control group in terms of the total and the subscale scores of CSHQ, including sleep onset delay, sleep duration, sleep anxiety, parasomnias, and sleep-disordered breathing (p < 0.001). There were no significant differences between the groups in terms of CCTQ total scores and sleep patterns (p > 0.05). Significant differences were found in PedsQL total and subscale scores, and ABC scores in children with DRE compared to the control group (p < 0.001). Children's Sleep Habits Questionnaire, PedsQL, and ABC scores were significantly correlated with each other in children with DRE.

CONCLUSIONS

Our results have shown that sleep habits and the quality of life are poor in children with DRE. Our study has shown that sleep disturbances, quality of life, and behavioral problems are strongly associated with each other in DRE. The recognition and appropriate treatment of sleep disturbances are important for improving the quality of life in children with DRE.

Sex differences in the relationship between morningness-eveningness components, mood and well-being among Bangladeshi university students

On the Morningness/Eveningness (M/E) continuum, eveningness has been related to mood disorder and poor well-being. M/E differs between men and women throughout their lifespan. However, there is a lack of information on sex differences in the relationship between M/E, mood, and well-being. This study aimed to test sex differences in the M/E, mood, and well-being relationship with consideration of two components of M/E, morning affect, and morning preference. A sample of 981 Bangladeshi university students (607 men) aged 18 to 27 (M = 21.95) completed Bangla versions of the Composite Scale of Morningness (CSM), BRUnel Mood Scale (BRUMS), and Positive Mental Health scale (PMH-scale) through an online survey. Multiple regression analyses were used to test the relationship of M/E components with mood and well-being. The results showed that the relationship between M/E, mood, and well-being was greater in women than in men. A lower score on both M/E components was related to higher negative moods (anger, confusion, depression, fatigue, and tension) and poor well-being. In regression analysis, only morning affect was found to be significant, which means that morning affect mainly contributes to the relation between M/E, mood, and well-being. Finally, sex by morning affect interaction indicated that the relation was higher for women. Therefore, higher eveningness could be more hazardous for women than men. Greater insight into the independent contribution of morning affect may facilitate understanding of the chronotype effects on psychological outcomes in men and women.

When early and late risers were left to their own devices: six distinct chronotypes under "lockdown" remained dissimilar on their sleep and health problems

Under national "lockdown," the habitual late risers need not wake up early, and, similarly to the early risers, they don't lose much sleep on weekdays. We tested whether, despite a decrease in weekday sleep loss, the difference between distinct chronotypes in health and sleep problems persisted during "lockdown." Two online surveys were conducted from 10th to 20th of May, 2020 and 2021, one of them after 6 non-working weeks and another after 14 working weeks (during and after "lockdown," respectively). Participants were students of the same grade at the same university department (572 and 773, respectively). The self-assessments included the Single-Item Chronotyping (SIC) designed for self-choosing chronotype among several their short descriptions and several questions about general health, mood state, outdoors and physical activity, and sleep concerns. The results suggested that the responses to each of the questions were not randomly distributed over 6 distinct chronotypes. Such a nonrandomness was identified within each of three pairs of these chronotypes, evening vs. morning types (with a rising throughout the day vs. a falling level of alertness, respectively), afternoon vs. napping types (with a peak vs. a dip of alertness in the afternoon, respectively), and vigilant vs. lethargic types (with the levels of alertness being permanently high vs. low, respectively). Morning, afternoon, and vigilant types reported healthier sleep/mood/behavior/habits than three other types. The most and the least healthy sleep/mood/behavior/habits were reported by morning and evening types, respectively. These relationships with health and sleep problems and the frequencies of 6 chronotypes remained unchanged after "lockdown." Such results, in particular, suggested that the association of evening types with poorer health and sleep might not be attributed to a big amount of weekday sleep loss. The accounting for this association might help in designing interventions purposed on reduction of sleep and health problems.

Biological Rhythm and Chronotype: New Perspectives in Health

The circadian rhythm plays a fundamental role in regulating biological functions, including sleep–wake preference, body temperature, hormonal secretion, food intake, and cognitive and physical performance. Alterations in circadian rhythm can lead to chronic disease and impaired sleep. The circadian rhythmicity in human beings is represented by a complex phenotype. Indeed, over a 24-h period, a person’s preferred time to be more active or to sleep can be expressed in the concept of morningness–eveningness. Three chronotypes are distinguished: Morning, Neither, and Evening-types. Interindividual differences in chronotypes need to be considered to reduce the negative effects of circadian disruptions on health. In the present review, we examine the bi-directional influences of the rest–activity circadian rhythm and sleep–wake cycle in chronic pathologies and disorders. We analyze the concept and the main characteristics of the three chronotypes.

The Effects of Genetic Background for Diurnal Preference on Sleep Development in Early Childhood

PURPOSE

No previous research has examined the impact of the genetic background of diurnal preference on children´s sleep. Here, we examined the effects of genetic risk score for the liability of diurnal preference on sleep development in early childhood in two population-based cohorts from Finland.

PARTICIPANTS AND METHODS

The primary sample (CHILD-SLEEP, CS) comprised 1420 infants (695 girls), and the replication sample (FinnBrain, FB; 962 girls) 2063 infants. Parent-reported sleep duration, sleep-onset latency and bedtime were assessed at three, eight, 18 and 24 months in CS, and at six, 12 and 24 months in FB. Actigraphy-based sleep latency and efficiency were measured in CS in 365 infants at eight months (168 girls), and in 197 infants at 24 months (82 girls). Mean standard scores for each sleep domain were calculated in both samples. Polygenic risk scores (PRS) were used to quantitate the genetic risk for eveningness (PRSBestFit) and morningness (PRS10kBest).

RESULTS

PRSBestFit associated with longer sleep-onset latency and later bedtime, and PRS10kBest related to shorter sleep-onset latency in CS. The link between genetic risk for diurnal preference and sleep-onset latency was replicated in FB, and meta-analysis resulted in associations (P<0.0005) with both PRS-values (PRSBestFit: Z=3.55; and PRS10kBest: Z=-3.68). Finally, PRSBestFit was related to actigraphy-based lower sleep efficiency and longer sleep latency at eight months.

CONCLUSION

Genetic liability to diurnal preference for eveningness relates to longer sleep-onset during the first two years of life, and to objectively measured lowered sleep efficiency. These findings enhance our understanding on the biological factors affecting sleep development, and contribute to clarify the physiological sleep architecture in early childhood.

Shorter and longer durations of sleep are associated with an increased twelve-month prevalence of psychiatric and substance use disorders: Findings from a nationally representative survey of US adults (NESARC-III)

The lack of comprehensive data on the association between psychiatric and substance use disorders and habitual sleep duration represents a major health information gap. This study examines the 12-month prevalence of mental disorders stratified by duration of sleep. Data were drawn from face-to-face interviews conducted in the National Epidemiologic Survey on Alcohol and Related Conditions III, a nationally representative survey of US adults (N = 36,309). There were 1893 (5.26%) participants who reported <5h of sleep/night; 2434(6.76%) 5 h/night; 7621(21.17%) 6 h/night; 9620(26.72%) 7 h/night; 11,186(31.07%) 8 h/night, and 3245(9.01%) ≥9 h/night. A U-shaped association was observed between sleep duration and all mental disorders. The prevalence of mental disorders was 55% for individuals with <5 h/night and 47.81% for ≥9 h/night, versus 28.24% for the 7 h/night (aOR = 1.90 and 1.39 respectively). The greatest odds ratios were for the <5 h/night group, with an increased risk above 3-fold for panic disorder (PD), post-traumatic stress disorder (PTSD), psychotic disorder, and suicide attempt; between 2 and 3 fold for major depressive disorder (MDD), bipolar disorder (BD), and generalized anxiety disorder (GAD); and between 1 and 2 fold for tobacco and drug use disorders, specific and social phobias. The ≥9 h/night group had an increased risk above 1 to 2-fold regarding tobacco and drug use disorders, MDD, BD, PD, social phobia, GAD, PTSD, psychotic disorder, and suicide attempt. U-shaped associations exist between sleep duration and mental disorders, calling for respect to recommendations for adequate sleep duration in routine clinical care as well as to actions for primary prevention in public health settings.

Childhood Sleep Functioning as a Developmental Precursor of Adolescent Adjustment Problems

Sleep has been linked to adjustment difficulties in both children and adolescents; yet little is known about the long-term impact of childhood sleep on subsequent development. This study tested whether childhood sleep problems, sleep quantity, and chronotype predicted internalizing and externalizing problems during adolescence. Latent Growth Modeling using the Czech portion of the European Longitudinal Study of Pregnancy and Childhood (N = 4393) was utilized to test the developmental trajectories of sleep characteristics (from 1.5 to 7 years) as predictors of adjustment problems trajectories (from 11 to 18 years). Findings provided evidence that children with higher levels of sleep problems at 1.5 years (and throughout childhood) reported higher levels of internalizing and externalizing problems at age 11. Additionally, greater eveningness at age 1.5 predicted a greater increase in externalizing problems from ages 11 to 18 years. The results emphasize the importance of childhood sleep problems in evaluating the risk of future adjustment difficulties.

Chronotypes and its association with psychological morbidity and childhood parasomnias

BACKGROUND

The relationship between chronotypes and sleeping problems is not clear. The objective of the study was to identify the relative occurrence of chronotypes among college students and to explore adult psychological morbidity and childhood sleeping problems across chronotypes.

MATERIALS AND METHODS

One hundred and fifty undergraduate medical students were assigned into different chronotypes by Morningness-Eveningness Questionnaire and they were further assessed using Self-Reporting Questionnaire, Parasomnia Questionnaire (adapted from the Adult Sleep Disorders Questionnaire), and Pittsburgh Sleep Quality Index.

RESULTS

Intermediate chronotype was the most common, seen in 87 (58%) students, followed by evening type in 34 (22.7%). Evening types have more difficulties in making a decision, becoming exhausted more easily and feeling worthless than other chronotypes. Evening-oriented students showed a significantly higher frequency of initial insomnia and poorer overall sleep quality than the other groups. The current bedwetting was more in evening types; there was no difference in any other current and childhood parasomnias.

CONCLUSIONS

Evening chronotypes had greater difficulty in decision-making, and they were more vulnerable to feel worthless. No significant association was found between childhood parasomnias and chronotypes except persistent bedwetting during adulthood in evening types.

Sleep Quantity and Problems as Mediators of the Eveningness-Adjustment Link during Childhood and Adolescence

Chronotype, or morningness/eveningness, has been associated with adjustment in both children and adolescents. Specifically, eveningness has been linked to adjustment difficulties; however, the mechanism underlying this association is poorly understood. The purpose of this study was to test whether the associations between eveningness and adjustment difficulties could be explained by an unfavorable impact of eveningness on sleep. Links from chronotype to internalizing problems and problem behaviors via sleep quantity and sleep problems were tested in a sample from the European Longitudinal Study of Pregnancy and Childhood (N = 3485; 48.8% female), both when the participants were children (7 years at T1, 11 at T2) and when they were adolescents (15 years at T1, 18 at T2). The findings provided evidence that eveningness predicted greater sleep problems and lower sleep quantity; however, only sleep problems predicted internalizing problems and problem behaviors. Sleep quantity did not mediate the eveningness-adjustment link, and sleep problems did so only in children. The findings show that sleep problems appear to be more important in explaining the eveningness-adjustment link rather than altered sleep quantity, commonly associated with eveningness.

Biological rhythm and emotional and behavioral problems among schoolchildren in Southern Brazil

Emotional and behavioral problems have been considered an indicative of mental disorder in children. Mental health problems affect 10-20% of children and adolescents living in low-income and middle-income countries. Evidence suggests that disruptions in the biological rhythm may be a primary cause of emotional and behavioral changes, which affects several psychological functions and moods. Thus, this study aimed at verifying the association between biological rhythm and emotional and behavioral problems in schoolchildren living in Southern Brazil. This is a cross-sectional study with a school-based sample conducted between August 2015 and November 2016. The presence of emotional and behavioral problems in children was verified by the Strengths and Difficulties Questionnaire (SDQ), parents' version. This is a 25-item assessment questionnaire used to screen mental health problems in children and adolescents (from 4 to 17 years of age) in the last 6 months. The Biological Rhythm Interview of Assessment in Neuropsychiatry-Kids (BRIAN-K) was used to measure the degree of biological rhythm disruption. The BRIAN-K consists of 20 items; from among these, 17 items are added to generate a quantitative measure, with greater scores indicating more biological rhythm disruption. The final score can also be divided into four subscales: sleep, social rhythm, eating pattern and overall activities. A total of 609 children responded to the assessment instruments. With regard to parents or primary caregiver, 596 completed the assessment and 13 (2%) were not located or refused to participate in the study. Thus, 596 dyads were included in the analysis. Children with emotional and behavioral problems presented higher scores in all domains of BRIAN-K: sleep, social, activity, eating pattern and total score (p < 0.001). The following variables remained associated with emotional and behavioral problems after adjusted analysis: BRIAN-K total score (p < 0.001) and all subscales sleep (p < 0.001), social (p < 0.001), activity (p < 0.001) and eating pattern (p < 0.001). Children with emotional and behavioral problems presented higher biological rhythm disruption when compared with children without emotional and behavioral problems. Our study emphasizes the importance of biological rhythm and its influence on emotional and behavioral problems in schoolchildren. Early detection of any biological rhythm disruption may enhance further assessment of any eventual emotional and behavioral problem and even a psychopathology.

State- and trait-like variation in morning and evening components of morningness-eveningness in winter depression

PURPOSE

Evening preference (eveningness) can be a risk factor for depression and a shift toward morning preference (morningness) can occur in response to treatment. A study of winter depression provides possibility to longitudinally evaluate state- and trait-like variation in morningness-eveningness during treatment in winter and remission in summer.

MATERIAL AND METHODS

Female patients with winter depression and controls without a psychiatric history (n = 54 and 32 with mean age ± standard deviation of 34.4 ± 11.0 and 35.7 ± 9.5 years, respectively) were treated with two-hour bright light for a week during winter period. Some of them (n = 40 and 19, respectively) were then restudied in summer. Measures obtained during the winter period from patients before and after treatment were compared to those obtained from controls and from the same patients in the summer period. Among compared measures, there were self-assessments of state- and trait-like differences in morning and evening components of morningness-eveningness.

RESULTS

The groups of depressed patients and controls differed in self-assessments of morning but not evening component of morningness-eveningness. The difference in state-like variation in morning component became non-significant after treatment and in summer. On the other hand, trait-like variation in this component demonstrated adequate test-retest (winter-summer) reliability, i.e. a shift toward trait-like eveningness persisted in patients in the summer.

CONCLUSIONS

The observed normalization of state-like variation in morning component of morning-evening preference can be mainly explained by the disappearance of such depressive symptoms as lack of energy, social withdrawal, loss of interest in once enjoyable activities, etc.

[Recognition of facial expressions of emotions by 3-year-olds depending on sleep and risk of depression]

INTRODUCTION

The emotional process is characterized by a negative bias in depression, thus it was legitimate to establish if they same is true in very young at-risk children. Furthermore, sleep, also proposed as a marker of the depression risk, is closely linked in adults and adolescents with emotions. That is why we wanted first to better describe the characteristics of emotional recognition by 3-year-olds and their links with sleep. Secondly we observed, if found at this young age, an emotional recognition pattern indicating a vulnerability to depression.

MATERIAL AND METHOD

We studied, in 133 children aged 36 months from the AuBE cohort, the number of correct answers to the task of recognition of facial emotions (joy, anger and sadness). Cognitive functions were also assessed by the WPPSI III at 3 years old, and the different sleep parameters (time of light off and light on, sleep times, difficulty to go to sleep and number of parents' awakes per night) were described by questionnaires filled out by mothers at 6, 12, 18, 24 and 36 months after birth. Of these 133 children, 21 children whose mothers had at least one history of depression (13 boys) were the high-risk group and 19 children (8 boys) born to women with no history of depression were the low-risk group (or control group).

RESULTS

Overall, 133 children by the age of 36 months recognize significantly better happiness than other emotions (P=0.000) with a better global recognition higher in girls (M=8.8) than boys (M=7.8) (P=0.013) and a positive correlation between global recognition ability and verbal IQ (P=0.000). Children who have less daytime sleep at 18 months and those who sleep less at 24 months show a better recognition of sadness (P=0.043 and P=0.042); those with difficulties at bedtime at 18 months recognize less happiness (P=0.043), and those who awaken earlier at 24 months have a better global recognition of emotions (P=0.015). Finally, the boys of the high-risk group recognize sadness better than boys in the control group (P=0.015).

CONCLUSION

This study confirms that the recognition of emotion is related to development with a female advantage and a link with the language skills at 36 months of life. More importantly, we found a relationship between sleep characteristics and emotional recognition ability and a negative bias in emotional recognition in young males at risk for depression.

Circadian Sleep Patterns in Toddlers Born Preterm: Longitudinal Associations with Developmental and Health Concerns

OBJECTIVE

Children born preterm are at elevated risk for several developmental and health concerns. Early sleep patterns may be associated with these concerns. The current study assesses the associations between toddler circadian sleep/activity patterns and later developmental, behavioral, attentional, and health concerns in this at-risk population.

METHOD

We examined circadian sleep/activity patterns at 2 years of age in 99 children born preterm. Child cognitive skills were tested at 3 years of age, and behavior, attention, and health concerns were reported at 3 and 6 years of age. First, sleep/activity data collected via actigraphy were assessed using time series analysis (TSA). For this, we assessed how each child's sleep/activity pattern compared to a specified 24-hour circadian cycle (SCC) with an adjustment for daytime napping. Second, in a series of regression models child sleep/activity parameters from the TSA were assessed with child gender, prematurity, and family sociodemographic assets as covariates.

RESULTS

Toddlers with patterns that closely aligned with the SCC had higher abbreviated intelligence quotient scores at 3 years of age. Additionally, at 6 years these children had a lower risk for illness-related medical visits. Higher toddler average activity level was associated with fewer teacher-reported attention-deficit hyperactivity disorder symptoms and a lower risk for illness-related medical visits.

CONCLUSION

The novel approach used in this study to index child circadian patterns provides a pattern-based analysis of sleep/activity, which may prove to be developmentally consequential. With replication, these findings may help practitioners promote optimal cognitive and health development via circadian sleep supports in infants born preterm.

Associations of chronotype with social jetlag and behavioral problems in preschool children

The timing, duration, and intensity of sleep are determined by the interaction between a sleep-wake-dependent homeostatic process and a sleep-wake-independent, intrinsic, clock-like circadian process. Chronotype represents individual differences in diurnal preferences, which are not only genetically determined but also influenced by social and environmental factors. Thus, the discrepancy between biological and social clocks, so-called "social jetlag", occurs. Chronotype, social jetlag, and the links between chronotype and behavioral problems are well documented in adults and adolescents. However, such studies on young children are limited. We conducted a survey of sleep and health for preschool children attending kindergarten or childcare centers in Wako, Okayama and Kurashiki cities, Japan, between May and July 2012. A total of 654 children aged 4-6 years (342 boys and 312 girls, with an average age of 4.7 years) were assessed using the Children's ChronoType Questionnaire and the Strength and Difficulties Questionnaire. Morning (M)-type, neither (N)-type and evening (E)-type accounted for 36.2%, 54.0% and 9.8% of the participants, respectively. The weekday-to-weekend differences in midsleep time--originally proposed as the concept of social jetlag--were 11, 25 and 35 min for M-, N- and E-types, respectively. There was a negative correlation between chronotype and sleep period during weekdays (p < 0.001) and a positive correlation on weekends (p < 0.001). The weekday-to-weekend difference in sleep period was 0.5 h for E-types, whereas there was no difference for M-types. Binomial logistic regression analyses were used to examine the links between chronotype and behavioral problems, adjusted for participants' sex, age, childcare programs and locations. Chronotype was significantly associated with hyperactivity/inattention: N-type (adjusted OR = 1.74, 95% CI = 1.03-2.95, p < 0.05) and E-type (adjusted OR = 2.47, 95% CI = 1.18-5.20, p < 0.05). E-type was significantly associated with conduct problems (adjusted OR = 2.11, 95% CI = 1.03-4.31, p < 0.05) and peer problems (adjusted OR = 2.75, 95% CI = 1.18-6.44, p < 0.05). The results suggest that E-type children are vulnerable to higher social jetlag and more behavioral problems. The immature adjustment function of their endogenous circadian pacemakers may not be able to correct a small but significant social jetlag to synchronize with their social clocks. Furthermore, guidance based on chronobiological evidence is required for parents, teachers and health professionals to help children achieve optimal sleep and reduce behavioral problems.

Chronotype is associated with the timing of the circadian clock and sleep in toddlers

Chronotype is a construct reflecting individual differences in diurnal preference. Although chronotype has been studied extensively in school-age children, adolescents and adults, data on young children are scarce. This study describes chronotype and its relationship to the timing of the circadian clock and sleep in 48 healthy children aged 30-36 months (33.4 ± 2.1 months; 24 males). Parents completed the Children's Chronotype Questionnaire (CCTQ) ~2 weeks before the start of the study. The CCTQ provides three measures of chronotype: midsleep time on free days, a multi-item morningness/eveningness score and a single item chronotype score. After 5 days of sleeping on their habitual schedule (assessed with actigraphy and sleep diaries), children participated in an in-home salivary dim light melatonin onset assessment. Average midsleep time on free days was 1:47 ± 0:35, and the average morningness/eveningness score was 26.8 ± 4.3. Most toddlers (58.4%) were rated as 'definitely a morning type' or 'rather morning than evening type', while none (0%) were rated as 'definitely evening type'. More morning types (midsleep time on free days and morningness/eveningness score, respectively) had earlier melatonin onset times (r = 0.45, r = 0.26), earlier habitual bedtimes (r = 0.78, r = 0.54), sleep onset times (r = 0.80, r = 0.52), sleep midpoint times (r = 0.90, r = 0.53) and wake times (r = 0.74, r = 0.34). Parent ratings using the single-item chronotype score were associated with melatonin onset (r = 0.32) and habitual bedtimes (r = 0.27), sleep onset times (r = 0.33) and sleep midpoint times (r = 0.27). Morningness may best characterize circadian preference in early childhood. Associations between chronotype and circadian physiology and sleep timing suggest adequate validity for the CCTQ in this age group. These findings have important implications for understanding the marked variability in sleep timing during the early years of life.

Clinical Implications of Impaired Sleep

Despite its pervasiveness in primary care, deficient sleep often is underappreciated as a cue to other health risks. Accordingly, this review discusses contemporary evidence-based perspectives on impaired sleep and its associations with other lifestyle medicine concerns, including obesity, cardiovascular conditions, psychological problems, and health-compromising habits. The potential clinical benefits of promoting sleep health also will be considered.

Human CLOCK gene-associated attention deficit hyperactivity disorder-related features in healthy adults: quantitative association study using Wender Utah Rating Scale

Circadian rhythm disturbance is highly prevalent in attention deficit hyperactivity disorder (ADHD). Recently, the association between the CLOCK gene and ADHD has been demonstrated in clinical samples, and the CLOCK gene's role was thought to be mediated by rhythm dysregulation. Meanwhile, ADHD has been suggested as the extreme end of a continuously distributed trait that can be found in the general population. Therefore, we examined two possibilities: (1) an ADHD-related continuous trait may be associated with the CLOCK gene, and (2) this association may be mediated by the degree of individuals' evening preference. To explore these possibilities, we performed a quantitative trait locus association study with a sample of 1,289 healthy adults. The Wender Utah Rating Scale (WURS) and the Composite Scale of Morningness (CSM) were utilized to measure the quantitative traits. Quantitative association analysis was performed using PLINK software. We found that rs1801260 (=T3111C) was associated with WURS scores in both allele-wise (p = 0.018) and haplotype-wise analyses (range of p values: 0.0155-0.0171) in male participants only. After controlling for the CSM total score as a covariate, the strength of the association did not change at all, suggesting that the association was not mediated by evening preference. Despite the very weak association signal, our results provide evidence that the CLOCK gene's association with ADHD in clinical samples may be generalizable to traits measured in the normal population. However, as our results failed to show a mediating role of evening preference, ongoing efforts are needed to identify the mechanisms by which the CLOCK gene determines ADHD-related traits.

Evening-type military veterans report worse lifetime posttraumatic stress symptoms and greater brainstem activity across wakefulness and REM sleep

Evening chronotypes exhibit increased rates of affective dyregulation and sleep disturbances (e.g., insomnia and nightmares). Such symptoms are common to military veterans with posttraumatic stress disorder (PTSD); however, the influence of chronotype on this population remains unknown. We examined behavioral, psychological, and neural correlates of chronotype in 36 combat-exposed military veterans with varying degrees of posttraumatic stress symptomatology. We employed FDG-PET to assess neural activity across wakefulness and rapid eye movement (REM) sleep. We used polysomnography and diaries to monitor sleep, and a self-report survey to measure chronotype. Eveningness was associated with greater lifetime PTSD symptoms, more disturbed sleep, and more frequent and intense nightmares. Eveningness was also associated with greater brain activity in posterior cingulate/precuneus and brainstem regions across wakefulness and REM sleep, overlapping with regions related to arousal and REM sleep generation. Chronotype may be an important correlate of neural activity in REM sleep-generating and/or arousal regulatory regions among combat-exposed veterans with PTSD symptoms. Further investigations of the role of chronotype in PTSD are warranted.