Abstract: Sleep disturbances comparable with insomnia occur in up to 80% of people with schizophrenia, but very little is known about the contribution of circadian coordination to these prevalent disruptions.

Abstract: Cognitive performance deteriorates during extended wakefulness and circadian phase misalignment, and some individuals are more affected than others. Whether performance is affected similarly across cognitive domains, or whether cognitive processes involving Executive Functions are more sensitive to sleep and circadian misalignment than Alertness and Sustained Attention, is a matter of debate.

Abstract: Individuals show variation in their preference for the daily timing of activities. In this study the authors analyzed whether chronotypes associate with sleep duration and sleep-related complaints. The authors used the National FINRISK Study 2007 Survey data on 3696 women and 3162 men, representative of the Finnish population aged 25 yrs and older, for the assessment of chronotype and self-reported sleep. Evening types experienced insomnia symptoms, had nightmares, and had used recently hypnotics significantly more often than other chronotypes among both men and women. In a multinominal logistic regression model predicting insufficient sleep, the association of eveningness with insufficient sleep was not abolished after adjustment for sex, age, and sleep duration. The prevalence of short sleepers was significantly higher in evening types among men than among women, whereas that of long sleepers was significantly higher in evening types among both men and women, as compared with the other chronotypes. Thes...

Abstract: Individuals show variation in their preference for the daily timing of activities. In this study the authors analyzed whether chronotypes associate with sleep duration and sleep-related complaints. The authors used the National FINRISK Study 2007 Survey data on 3696 women and 3162 men, representative of the Finnish population aged 25 yrs and older, for the assessment of chronotype and self-reported sleep. Evening types experienced insomnia symptoms, had nightmares, and had used recently hypnotics significantly more often than other chronotypes among both men and women. In a multinominal logistic regression model predicting insufficient sleep, the association of eveningness with insufficient sleep was not abolished after adjustment for sex, age, and sleep duration. The prevalence of short sleepers was significantly higher in evening types among men than among women, whereas that of long sleepers was significantly higher in evening types among both men and women, as compared with the other chronotypes. Thes...

Abstract: Background: Two understudied risk factors that have been linked to emotional difficulties in adolescence are chronotype and sleep deprivation. This study extended past research by using an experimental design to investigate the role of sleep deprivation and chronotype on emotion in adolescents. It was hypothesized that sleep deprivation and an evening chronotype would be associated with decreased positive affect (PA), increased negative affect (NA), and lower positivity ratios. Methods: Forty-seven healthy adolescents (aged 10–15 for girls, 11–16 for boys) participated in a sleep deprivation and a rested condition. A subsample of 24 adolescents was selected on the basis of extreme morningness or eveningness scores (based on outer quartiles of scores on the Children’s Morningness-Eveningness Preferences Scale). PA and NA were measured using the Positive and Negative Affect Schedule for Children, and positivity ratios were calculated by dividing PA by NA. Results: Participants reported less positive affect and lower positivity ratios when sleep deprived, relative to when rested. Evening chronotypes reported less positive affect and lower positivity ratios than morning chronotypes in both rested and sleep deprivation conditions. Conclusions: These findings extend previous research by suggesting that adolescents are adversely impacted by sleep deprivation, and that an evening chronotype might serve as a useful marker of emotional vulnerability. Early intervention and prevention strategies can focus on improving sleep and on using chronotherapy principles to reduce eveningness.

Abstract: Students who work during the school year face the potential of sleep deprivation and its effects, since they have to juggle between school and work responsibilities along with social life This may leave them with less time left for sleep than their nonworking counterparts Chronotype is a factor that may exert an influence on the sleep of student workers Also, light and social zeitgebers may have an impact on the sleep-related problems of this population This study aimed to document sleep, light exposure patterns, social rhythms, and work-related fatigue of student workers aged 19-21 yrs and explore possible associations with chronotype A total of 88 student workers (mean ± SD: 2018 ± 44 yrs of age; 36 males/52 females) wore an actigraph (Actiwatch-L; Mini-Mitter/Respironics,Bend, OR) and filled out the Social Rhythm Metric for two consecutive weeks during the school year Also, they completed the Morningness-Eveningness Questionnaire (MEQ), Epworth Sleepiness Scale (ESS), Pittsburgh Sleep Quality Index (PSQI), and Occupational Fatigue Exhaustion/Recovery Scale (OFER) Repeated and one-way analyses of variance (ANOVAs), Pearson's chi-square tests, and correlation coefficients were used for statistical comparisons Subjects slept an average of 06:28 h/night Actigraphic sleep parameters, such as sleep duration, sleep efficiency, wake after sleep onset, and sleep latency, did not differ between chronotypes Results also show that evening types (n = 17) presented lower subjective sleep quality than intermediate types (n = 58) and morning types (n = 13) Moreover, evening types reported higher levels of chronic work-related fatigue, exhibited less regular social rhythms, and were exposed to lower levels of light during their waking hours (between 2 and 11 h after wake time) as compared to intermediate types and morning types In addition, exposure to light intensities between 100 and 500 lux was lower in evening types than in intermediate types and morning types However, bright light exposure (≥ 1000 lux) did not differ between chronotypes In conclusion, results suggest that student workers may constitute a high-risk population for sleep deprivation Evening types seemed to cope less well with sleep deprivation, reporting poorer sleep quality and higher levels of work-related fatigue than intermediate types and morning types The higher chronic work-related fatigue of evening types may be linked to their attenuated level of light exposure and weaker social zeitgebers These results add credence to the hypothesis that eveningness entails a higher risk of health-impairing behaviors

Abstract: To explore the influence of circadian rhythms on executive function during early adolescence, we administered a battery of executive function measures (including a Go-Nogo task, the Iowa Gambling Task, a Self-ordered Pointing task, and an Intra ⁄ Extradimensional Shift task) to Morning-preference and Evening-preference participants (N = 80) between the ages of 11 and 14 years who were tested in the morning or afternoon. Significant Chronotype · Time of Day interactions (controlling for amount of sleep the previous night) revealed that adolescents tested at their optimal times of day performed better than those tested at their nonoptimal times. Implications for our understanding of physiological arousal, sleep, and executive function during adolescence are discussed.

Abstract: There are substantial age and individual differences in chronotype, or patterns of sleep/wake activity and energy levels that are tied to time of day and governed by internal circadian and sleep drives (Horne & Ostberg, 1977; May & Hasher, 1998; Mongrain, Carrier, & Dumont, 2006; Roenneberg et al., 2007). Morning types, or “larks,” wake up early, plan activities early in the day and tend to retire early in the evening. In contrast, evening types, or “owls,” awake later and are often active until late at night. Of course, many individuals fall between these two extremes (Horne & Ostberg, 1977). Research on young adults suggests that larks and owls differ in terms of well-being and susceptibility to psychiatric illness. For example, morningness is associated with a more stable personality (DeYoung, Hasher, Djikic, Criger, & Peterson, 2007) and greater subjective well-being (Randler, 2008). In contrast, eveningness is associated with increased susceptibility to depression (Drennan, Klauber, Kripke, & Goyette, 1991; Kitamura et al., 2010) and increased alcohol and stimulant use (Wittmann, Dinich, Merrow, & Roenneberg, 2006). Evening types are also more likely to report being in fair or poor general health (Paine, Gander, & Travier, 2006). Central to these differences in well-being and psychopathology may be variations in emotional state: Morningness among younger adults is associated with higher positive affect across the day (Clark et al., 1989; Hasler, Allen, Sbarra, Bootzin, & Bernert, 2010). Morning types also score higher on measures of energy-alertness and lower on tiredness compared with evening types (Froberg, 1977). In contrast, negative affect does not appear to vary with chronotype (Clark et al., 1989; Hasler et al., 2010). Thus, existing evidence suggests an association between chronotype and affect, with morning types reporting greater overall experience of emotions associated with positive activation, including excitement, cheerfulness, and alertness, compared with individuals with later time of day preferences. This conclusion, however, is based solely on data from younger adults, and may be limited because the individuals in this age range show very different time of day preferences compared to individuals of other ages. While morning chronotypes are most common during childhood, there are more evening types in adolescence, reaching a peak at around age 19 in women and 21 in men (Kim, Dueker, Hasher, & Goldstein, 2002; Roenneberg et al., 2007). Thereafter, there are greater morningness tendencies in each subsequent age group, such that by age 60, a majority of individuals report feeling at their best in the morning (May & Hasher, 1998; Mecacci, Zani, Rocchetti, & Lucioli, 1986). These chronotype differences are thought to be linked to age-dependent changes in the concentration and timing of certain hormones, including cortisol and growth hormone, which influence the timing and quality of sleep (Roenneberg et al., 2007; Van Cauter, Leproult, & Plat, 2000). Although longitudinal evidence is lacking, retrospective self-assessments of chronotype for various stages in development support the pattern of cross-sectional differences (Roenneberg et al., 2007). Thus, older adults (ages 60 – 80) markedly differ from younger adults in terms of chronotype; their sleep–wake times are shifted earlier as is their preferred time for activities. Given substantial age-related differences in chronotype patterns, it is unknown whether the relationship between morningness and emotional state observed in younger adults also holds for older adults. There is evidence that positive affect and subjective well-being are higher in older adulthood (Carstensen et al., 2011; Mroczek & Kolarz, 1998; Stone, Schwartz, Broderick, & Deaton, 2010). Considering the association between morningness and age, this raises an intriguing possibility: Reports of age differences in positive affect may be tied to the greater proportion of morning-type individuals age 60 and above. In addition, given previous evidence that evening-type individuals are more likely to report being in poorer health (Paine et al., 2006), it is also possible that chronotype may contribute to individual differences in older adults’ subjective health ratings. Subjective health is an important component of well-being and is known to be a strong predictor of objective health outcomes and mortality in older people (Idler & Benyamini, 1997). To address the question of whether the association between morningness and well-being exists in older adults, we obtained measures of chronotype, affect and subjective health in both younger (ages 17–38) and older adults (ages 59 –79). Because older adults report both improved positive affect and a stronger tendency toward morningness, we also tested whether age differences in chronotype partially explain age-related differences in well-being.

Abstract: Objective The objective of this study was to evaluate the sleep quality, sleepiness, chronotype and the anxiety level of Brazilian Paralympics athletes before the 2008 Beijing Paralympic Games. Design Cross-sectional study. Setting Exercise and Psychobiology Studies Center (CEPE) and Universidade Federal de Sao Paulo, an urban city in Brazil. Participants A total of 27 Paralympics athletes of both genders (16 men and 11 women) with an average age of 28±6 years who practised athletics (track and fi eld events) were evaluated. Main outcome measures Sleep quality was evaluated using the Pittsburgh Scale and the Epworth Sleepiness Scale to evaluate sleepiness. Chronotype was determined by the Horne and Ostberg questionnaire and anxiety through the State-Trait Anxiety Inventory. The evaluations were performed in Brazil 10 days before the competition. Results The study’s results demonstrate that 83.3% of the athletes that presented excessive daytime sleepiness also had poor sleep quality. The authors noted that 71.4% were classifi ed into the morning type and 72% of the athletes who presented a medium anxiety level also presented poor sleep quality. Athletes with poor sleep quality showed signifi cantly lower sleep effi ciency (p=0.0119) and greater sleep latency (p=0.0068) than athletes with good sleep quality. Athletes who presented excessive daytime sleepiness presented lower sleep effi ciency compared to nonsleepy athletes (p=0.0241). Conclusions The authors conclude that the majority of athletes presented poor sleep quality before the competition. This information should be taken into consideration whenever possible when scheduling rest, training and competition times.

Abstract: Path analysis was used to examine the relationship between class start times, sleep, circadian preference, and academic performance in college-aged adults. Consistent with observations in middle and high school students, college students with later class start times slept longer, experienced less daytime sleepiness, and were less likely to miss class. Chronotype was an important moderator of sleep schedules and daytime functioning; those with morning preference went to bed and woke up earlier and functioned better throughout the day. The benefits of taking later classes did not extend to academic performance, however; grades were somewhat lower in students with predominantly late class schedules. Furthermore, students taking later classes were at greater risk for increased alcohol consumption, and among all the factors affecting academic performance, alcohol misuse exerted the strongest effect. Thus, these results indicate that later class start times in college, while allowing for more sleep, also increase the likelihood of alcohol misuse, ultimately impeding academic success.

Abstract: Circadian variations have been found in human performance, including the efficiency to execute many tasks, such as sensory, motor, reaction time, time estimation, memory, verbal, arithmetic calculations, and simulated driving tasks. Performance increases during the day and decreases during the night. Circadian rhythms have been found in three basic neuropsycho- logical processes (attention, working memory, and executive functions), which may explain oscillations in the performance of many tasks. The time course of circadian rhythms in cognitive performance may be modified significantly in patients with brain disorders, due to chronotype, age, alterations of the circadian rhythm, sleep deprivation, type of disorder, and medication. This review analyzes the recent results on circadian rhythms in cognitive performance, as well as the implications of these rhythms for the neuropsychological assessment of patients with brain disorders such as traumatic head injury, stroke, dementia, developmental disorders, and psychiatric disorders.

Abstract: Human morning and evening chronotypes differ in their preferred timing for sleep and wakefulness, as well as in optimal daytime periods to cope with cognitive challenges. Recent evidence suggests that these preferences are not a simple by-product of socio-professional timing constraints, but can be driven by inter-individual differences in the expression of circadian and homeostatic sleep-wake promoting signals. Chronotypes thus constitute a unique tool to access the interplay between those processes under normally entrained day-night conditions, and to investigate how they impinge onto higher cognitive control processes. Using functional magnetic resonance imaging (fMRI), we assessed the influence of chronotype and time-of-day on conflict processing-related cerebral activity throughout a normal waking day. Sixteen morning and 15 evening types were recorded at two individually adapted time points (1.5 versus 10.5 hours spent awake) while performing the Stroop paradigm. Results show that interference-related hemodynamic responses are maintained or even increased in evening types from the subjective morning to the subjective evening in a set of brain areas playing a pivotal role in successful inhibitory functioning, whereas they decreased in morning types under the same conditions. Furthermore, during the evening hours, activity in a posterior hypothalamic region putatively involved in sleep-wake regulation correlated in a chronotype-specific manner with slow wave activity at the beginning of the night, an index of accumulated homeostatic sleep pressure. These results shed light into the cerebral mechanisms underlying inter-individual differences of higher-order cognitive state maintenance under normally entrained day-night conditions.

Abstract: While insomnia is a well-established risk factor for the initial onset, recurrence or relapse of affective disorders, the specific characteristics of insomnia that confer risk remain unclear. Patients with insomnia with an evening chronotype may be one particularly high-risk group, perhaps due to alterations in positive affect and its related affective circuitry. We explored this possibility by comparing diurnal patterns of positive affect and the activity of positive affect-related brain regions in morning- and evening-types with insomnia. We assessed diurnal variation in brain activity via the relative regional cerebral metabolic rate of glucose uptake by using [(18) F]fluorodeoxyglucose-positron emission tomography during morning and evening wakefulness. We focused on regions in the medial prefrontal cortex and striatum, which have been consistently linked with positive affect and reward processing. As predicted, chronotypes differed in their daily patterns in both self-reported positive affect and associated brain regions. Evening-types displayed diurnal patterns of positive affect characterized by phase delay and smaller amplitude compared with those of morning-types with insomnia. In parallel, evening-types showed a reduced degree of diurnal variation in the metabolism of both the medial prefrontal cortex and the striatum, as well as lower overall metabolism in these regions across both morning and evening wakefulness. Taken together, these preliminary findings suggest that alterations in the diurnal activity of positive affect-related neural structures may underlie differences in the phase and amplitude of self-reported positive affect between morning and evening chronotypes, and may constitute one mechanism for increased risk of mood disorders among evening-type insomniacs.

Abstract: There has been a lot of international research on morning/evening preference, but relatively little has been done in mainland China. This study investigated whether the trend for increased morning preference in older adults, which has been a consistent finding in chronotype research in many countries, is also found in Chinese. Using the Chinese translation of the MorningnessEveningness Questionnaire (MEQ), it was found that a sample of 305 Beijing residents, aged 1887, showed a significant correlation between MEQ score and age (r = 0.595), and that participants aged 50+ showed significantly more morning preference compared to younger participants. Additionally, a reliability assessment of the 5-question reduced MEQ (rMEQ) was undertaken. Testretest assessment, involving a separate sample (n= 114), showed significant correlations between rMEQ and MEQ scores (r = 0.768), and between chronotype classifications (r = 0.524), supporting the reliability of the Chinese rMEQ.

Abstract: Boschloo, A., Ouwehand, C., Dekker, S., Lee, N., De Groot, R., Krabbendam, L., & Jolles, J. (2012). The relation between breakfast skipping and school performance in adolescents. Mind, Brain, and Education, 6(2), 81-88. doi:10.1111/j.1751-228x.2012.01138.x

Abstract: OBJECTIVE Morningness/eveningness (M/E) is a stable characteristic of individuals. Circadian rhythms are altered in episodes of mood disorder. Mood disorder patients were more evening-type than normal population. In this study, we compared the characteristics of M/E among the 257 patients with bipolar I disorder (BPD1), bipolar II disorder (BPD2) and major depressive disorder, recurrent (MDDR). METHODS M/E was evaluated using the Korean version of the composite scale of morningness (CS). Factor analysis was done to extract specific elements of circadian rhythm (morning preference, morning alertness, and evening tiredness). The total score and scores for factors and individual items of CS were compared in order to evaluate differences among the three different diagnostic groups. Factor scores of CS were different among the diagnostic groups. RESULTS BPD1 subjects had a higher score for evening tiredness than BPD2 subjects (p=0.060), and BPD1 subjects had a significantly higher score for morning alertness than subjects with MDDR (p=0.034). This difference was even more profound for the representative item scores of each factor; item 2 of CS for evening tiredness (BPD1>BPD2, p=0.007) and item 5 of CS for morning alertness (BPD1>MDDR, p=0.002). Total score of CS were not different among 3 diagnostic groups. CONCLUSION Circadian rhythm characteristics measured by CS were different among BPD1, BPD2, and MDDR. BPD2 showed more eveningness than BPD1. MDDR showed less morningness than BPD1. CS would be a reasonable endophenotype associated with mood disorders. More studies with large sample size of mood disorders on M/E are warranted.

Abstract: Accumulating evidence suggests that evening-type adolescents are exposed to a number of determinants that might have a negative impact on their health condition. Given that few studies have investigated the association between chronotype and quality of life measures in large samples of adolescents, the aim of this study was to assess the relationship between morningness-eveningness and health-related quality of life among 1600 adolescents (aged 12-16 years). Adolescents completed the Vecu et Sante Percue de L'adolescent (VSP-A) and the Morningness-Eveningness Scale for Children (MESC). Girls and older adolescents reported worse health indicators and were more evening oriented. Evening-type adolescents obtained lower scores on vitality, physical and psychological well-being, body image, relations with parents, relations with teachers, school work and global health scale.

Abstract: Previous studies have provided evidence that eveningness could be related to disadvantageous individual characteristics The hypothesis that more evening-oriented individuals exhibit lower satisfaction with life has been tested by Randler using a sample of 164 German university students, and this showed that eveningness is associated with lower satisfaction with life (r = 177) The aim of the present study was to answer the question of whether or not this relationship is culturally independent, and would exist if a sample from another geographical location and culture had been studied A sample of 349 residents (149 men) aged between 13 and 59 yrs from two Polish cities completed the Morningness-Eveningness Questionnaire and the Satisfaction with Life Scale Analysis revealed that morningness was related to greater life satisfaction (r = 105), regardless of age and sex The magnitude of this relationship did not differ significantly between the Polish and the German sample, which suggests that the magni

Abstract: The human circadian clock regulates the daily timing of sleep, alertness and performance and is synchronized to the 24-h day by the environmental light-dark cycle. Bright light exposure has been shown to positively affect sleepiness and alertness, yet little is known about its effects on physical performance, especially in relation to chronotype. We, therefore, exposed 43 male participants (mean age 24.5 yrs ± SD 2.3 yrs) in a randomized crossover study to 160 minutes of bright (BL: ≈ 4.420 lx) and dim light (DL: ≈ 230 lx). During the last 40 minutes of these exposures, participants performed a bicycle ergometer test. Time-of-day of the exercise sessions did not differ between the BL and DL condition. Chronotype (MSF(sc), mid-sleep time on free days corrected for oversleep due to sleep debt on workdays) was assessed by the Munich ChronoType Questionnaire (MCTQ). Total work was significantly higher in BL (median 548.4 kJ, min 411.82 kJ, max 875.20 kJ) than in DL (median 521.5 kJ, min 384.33 kJ, max 861.23 kJ) (p = 0.004) going along with increased exhaustion levels in BL (blood lactate (+12.7%, p = 0.009), heart rate (+1.8%, p = 0.031), and Borg scale ratings (+2.6%, p = 0.005)) in all participants. The differences between total work levels in BL and DL were significantly higher (p = 0.004) if participants were tested at a respectively later time point after their individual mid-sleep (chronotype). These novel results demonstrate, that timed BL exposure enhances physical performance with concomitant increase in individual strain, and is related not only to local (external) time, but also to an individual's internal time.

Abstract: The aim of the present study was to investigate, for the first time, the relationship between circadian preference and mood seasonality in adolescents. To this end, 1539 participants (881 female; 658 male) completed the Morningness-Eveningness Questionnaire for Children and Adolescents and the Seasonal Pattern Assessment Questionnaire for Children and Adolescents to determine circadian preference and mood seasonality, respectively. Evening types achieved significantly higher mood seasonality scores than intermediate and morning types, as intermediates did than morning types. Agreeing with previous studies on young adults and adults, the present data indicate a significant relationship between eveningness and higher mood seasonality in adolescents.

Abstract: The study investigates the effect of the month of birth and ambient light conditions at birth on sleep length and chronotype among residents of high latitudes. The authors surveyed 1172 persons (609 girls, 563 boys) age 11 to 18 yrs living in five villages and four towns located between 59.5°N and 67.6°N latitude. Survey participation was voluntary and anonymous. Sleep length and chronotype were assessed using the Munich chronotype questionnaire (MCTQ). The study showed the sleep length and chronotype of the children and adolescents depended on sex, age, type of settlement (town/village), and latitude of residence. Latitude exerted a stronger impact on sleep length and chronotype of children and adolescents living in villages than on those of their urban counterparts. Month of birth had no effect on sleep length and chronotype. There was a significant effect of the time of sunrise, sunset, and day length at birth on the chronotype of children and adolescents. A later chronotype was observed in the sample ...

Abstract: There are few studies suggesting that chronotype or morningness-eveningness (M/E) is a predictor of depressive symptoms. A sample of 277 women (university students) of a mean age of 22.25 years ± (SD) 2.47 participated in this study. We used the Composite Scale of Morningness to assess circadian typology, the Patient Health Questionnaire (PHQ-9) to assess depressive symptomatology, and – because M/E as well as depressive symptoms are associated with personality – we controlled for personality using a short measure of the Big Five Inventory as well as including a scale to measure hypochondriasis. There were 28 women classified with moderate, one with moderately severe, and three with severe depression. Negative correlations existed between CSM score, average sleep duration, extraversion, conscientiousness, and PHQ-9 scores, and positive correlations between hypochondriasis, neuroticism, and PHQ-9 scores. In a hierarchical regression, the model predicts 28% of variance in the PHQ-9 scores. Personality expla...