Association between morningness-eveningness and behavioral/emotional problems among adolescents

Adolescent eveningness is associated with age, parental monitoring, daytime sleepiness, sleep problems, moodiness, and the use of coffee. This study investigated the association between adolescent morningness-eveningness and psychopathology, substance use, and suicidality in 1332 students ages 12 to 13. Each student-participant completed the Chinese version of the Child Morningness/Eveningness Scale (CMES), the Pubertal Development Scale, and a questionnaire about their sleep schedule, trouble sleeping, habitual substance use, and suicidality. Their mothers completed the Child Behavioral Checklist and Chinese Health Questionnaire. The morning (n = 412), intermediate (n = 740), and evening (n = 180) groups were operationally defined by the CMES t scores. The mixed model was used for data analysis. The evening group had shorter weekday sleep time, longer weekend sleep time, more daytime napping, and greater sleep compensation on weekends and was more likely than the other 2 groups to have behavioral/emotional problems, suicidality, and habitual substance use. Internalizing and externalizing problems partially explained the association between eveningness, substance use, and suicidality. The findings suggest that eveningness may be an indicator for adolescents with behavioral/emotional problems and risky behaviors and suggest an investigation for possible intervention.     

Morningness–eveningness interferes with perceived health,physical activity,diet and stress levels in working women: A cross-sectional study

Sleep and health are closely interrelated and sleep quality is a well-known contributor to perceived health. However, effects of sleep-timing preference i.e. morningness–eveningness on health has yet to be revealed. In this study, we explored the relationship between morningness–eveningness and perceived health in a sample of female working professionals (N?=?202). Sleep-timing preference was measured using the Composite Scale of Morningness. Perceived health was characterized by Center for Epidemiologic Studies Depression Scale, WHO Well-Being Scale-5 and Patient Health Questionnaire-15 scores. We also investigated possible mechanisms, including stress and health-impairing behaviours. In accordance with previous data, we found more depressive mood, lower well-being and poorer perceived health among evening types. To assess health-impairing behaviours we collected data on smoking habits, alcohol consumption, physical activity and diet. Among the possible mechanism variables, greater stress, less frequent physical activity and less healthy diet were associated with eveningness. Furthermore, stress diminished the strength of the association between morningness–eveningness and depressed mood. Physical activity attenuated the strength of the association between morningness–eveningness and well-being. No effects of alcohol consumption could be identified. Our data show that evening preference behaves as a health risk in terms of associating with poor perceived health. Our findings also suggest that this effect might be mediated by health behaviours and stress.     

Angry night birds: Emotionality,activity and sociability temperament in adolescent chronotypes

ABSTRACT

There is growing interest in personality profiles associated with morningness–eveningness to foster an understanding of the behaviors and mental states of chronotypes. This study aimed to analyze the domains of emotionality, activity and sociability (EAS) temperament in relation to morningness–eveningness in adolescents. A sample of 539 school pupils aged 13–19 years completed the EAS Temperament Survey, the Composite Scale of Morningness and the Munich Chronotype Questionnaire. Amongst the five EAS domains (emotionality-distress, emotionality-fearfulness, emotionality-anger, activity and sociability), greater emotionality-anger was related to eveningness, while greater emotionality-distress was related to lower social jet lag. The results suggest that evening chronotypes can be temperamentally inclined to anger. The possible mechanisms of this association are discussed.     

Clinical correlates of chronotypes in young persons with mental disorders

While important changes in circadian rhythms take place during adolescence and young adulthood, it is unclear how circadian profiles during this period relate to emerging mental disorders. This study aimed to: (i) characterise morningness–eveningness preference in young people with primary anxiety, depression, bipolar or psychotic disorders as compared to healthy controls, and (ii) to investigate associations between morningness–eveningness preference and the severity of psychiatric symptoms. Four hundred and ninety-six males and females aged between 12 and 30 years were divided into five groups according to primary diagnosis. The Hamilton Depression Rating Scale and the Brief Psychiatric Rating Scale were administered by a research psychologist and participants completed the Kessler Psychological Distress Scale and the Horne–Östberg Morningness–Eveningness Questionnaire (ME). ME scores were significantly lower (i.e. higher levels of “eveningness”) in all patient diagnosis subgroups compared to the control group. The psychosis group had higher ME scores than the depression and anxiety groups. Compared to the control group, the anxiety, depression and bipolar subgroups had a significantly higher proportion of “moderate evening” types, with a similar trend for the psychosis group. The proportion of “extreme evening” types was significantly higher in the anxiety and depression subgroups than in the control group. Lower ME scores correlated with worse psychological distress in males from the bipolar group. Lower ME scores correlated with higher depression severity in females with depression and in males with bipolar disorder. These results suggest that young persons with various mental disorders, especially those with affective disorders, present with a stronger “eveningness” preference and higher rates of evening chronotypes than healthy controls from the same age group. Later chronotypes were generally associated with worse psychological distress and symptoms severity. These associations were modulated by sex and primary diagnosis.     

Morningness–eveningness and treatment response in major depressive disorder

In a large, prospective, 8-week open study of 721 outpatients receiving agomelatine treatment for a current major depressive episode (MDE), morningness–eveningness (Composite Scale of Morningness) was assessed before and after treatment to investigate possible changes in morningness–eveningness after treatment and evaluate whether morningness–eveningness at baseline predicted treatment response. A change towards morningness was observed after treatment. This change was greater in responders than non-responders. Moreover, being a morning type at baseline was an independent predictor of response to treatment. Once thought to be a trait variable, morningness–eveningness is a potential treatment target that should be systematically assessed in MDE patients.     

Associations between diurnal preference,impulsivity and substance use in a young-adult student sample

ABSTRACT

A diurnal preference for eveningness is common in young adulthood and previous research has associated eveningness with anxiety symptoms as well as increased smoking and alcohol use behaviors. There is some evidence that impulsivity might be an important explanatory variable in these associations, but this has not been comprehensively researched. Here we used both subjective and objective measures of impulsivity to characterize impulsive tendencies in young adults and investigated whether trait impulsivity or trait anxiety could mediate the link between eveningness and substance use. A total of 191 university students (169 females), age range 18–25 y, completed the study. Diurnal preference, sleep quality, anxiety, impulsivity, and substance use were assessed by questionnaire. Impulsivity was also measured using a delay discounting task. Eveningness correlated with trait anxiety and trait impulsivity, and these associations were still significant after controlling for sleep quality. On the delayed discounting task, eveningness correlated with a tendency to prefer smaller immediate rewards over delayed, larger ones. Evening types also reported higher levels of alcohol and cigarette use even after controlling for sleep quality. These associations were found to be completely mediated by self-reported impulsivity; anxiety did not contribute. The current results could help inform interventions aiming to reduce substance use in young adult populations.     

Perceived morningness–eveningness predicts academic adjustment and substance use across university,but social jetlag is not to blame

Past research has consistently found that evening-types typically report poorer academic adjustment and higher levels of substance use compared to morning-types. An important development within the morningness–eveningness and psychosocial adjustment literature has been the hypothesis that social jetlag (i.e. the asynchrony between an individual’s “biological” and “social” clocks) is one factor that may explain why evening-types are at a greater risk for negative psychosocial adjustment. Yet, only a handful of studies have assessed social jetlag. Furthermore, the few studies that have assessed social jetlag have done so only with concurrent data, and thus have not been able to determine the direction of effects among morningness–eveningness, social jetlag and psychosocial adjustment. To address this important gap in the literature, the present 3-year longitudinal study employed the use of a cross-lagged auto-regressive model to specifically examine the predictive role of perceived morningness–eveningness and social jetlag on two important indices of psychosocial adjustment among university students: academic adjustment and substance use. We also assessed whether there would be an indirect effect between perceived morningness–eveningness and psychosocial adjustment through social jetlag. Participants were 942 (71.5% female; M?=?19 years, SD?=?0.90) undergraduates at a mid-sized university in Southern Ontario, Canada, who completed a survey at three assessments, each one year apart, beginning in first-year university. Measures were demographics (age, gender and parental education), sleep problems, perceived morningness–eveningness, social jetlag, academic adjustment and substance use. As hypothesized, results of path analyses indicated that a greater perceived eveningness preference significantly predicted higher social jetlag, poorer academic adjustment and higher substance use over time. In contrast, we found no support for social jetlag as a predictor of academic adjustment and substance use, indicating that social jetlag did not explain the link between perceived morningness–eveningness and negative psychosocial adjustment. An important finding was the significant predictive effect of higher substance use on social jetlag over time. Results of the present study highlight the importance of employing a longitudinal framework within which to specifically determine the direction of effects among the study variables in order to validate proposed theoretical models that aim to guide our understanding of how perceived morningness–eveningness, social jetlag, academic adjustment and substance use relate to each other.     

Morningness/eveningness and satisfaction with life in a Polish sample

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 magnitude and direction of association between morningness/eveningness and satisfaction with life could be independent of culture or geographical location.     

Eveningness and poor sleep quality contribute to depressive residual symptoms and behavioral inhibition in patients with bipolar disorder

ABSTRACT

Eveningness and sleep disturbances are considered as markers of Bipolar Disorder (BD) and influence mood and emotional or behavioral states. This study investigates the associations between circadian markers and sleep quality on residual depressive symptoms and inhibition/activation dimensions during the euthymic phase. A sample of 89 euthymic adult individuals with BD was assessed for circadian preference and typology using the Composite Scale of Morningness (CSM) and the Circadian Type Inventory (CTI) and for sleep quality using the Pittsburgh Sleep Quality Index (PSQI). The Montgomery and Asberg Depression Rating Scale (MADRS) and the Multidimensional Assessment of Thymic States (MAThyS) were used to measure residual depressive symptoms and the inhibition/activation dimensions. We examined any associations between these parameters using correlations and path analyses. We identified significant associations between eveningness and poorer sleep quality that correlated to higher depressive residual symptoms and a global inhibition. The use of path analyses led us to conclude that poor sleep quality mediated the relationship between eveningness and either residual mood symptoms or behavioral inhibition (motivation, sensory perception, interpersonal interaction, and cognition). These factors should be considered in the clinical evaluation of individuals with BD, with a specific attention during the euthymic phase, in order to achieve the best functional outcome possible.     

The influence of subjective sleep quality on the association between eveningness and depressive symptoms

Increasing evidence suggests that eveningness is associated with increased risk for depression. Eveningness, however, is also associated with poor sleep quality and the unique role of eveningness in depressive symptomatology remains to be elucidated. The goal of the current study, therefore, was to examine the inter-relationships between eveningness, subjective sleep quality and depressive symptoms in healthy participants free of current or previous depression and sleep disorder. Here, 167 healthy participants (mean age 24.16, 129/38 females/males) completed the reduced Morningness–Eveningness Questionnaire (rMEQ), the Pittsburgh Sleep Quality Index (PSQI) and the Centre for Epidemiological Studies Depression Scale (CES-D). Bootstrap mediation analysis for a simple mediation model including rMEQ, PSQI and CES-D was applied. Eveningness was associated with increased depressive symptoms and mediation analysis showed that this relationship was partly mediated by sleep quality. Our results suggest that indicators of depression observed in evening-type individuals cannot be attributed exclusively to disturbed sleep. We suggest that interventions that target both sleep quality and dysfunctional cognitive styles would be optimal to promote well-being in evening-type individuals.     

Facebook Use Predicts Declines in Subjective Well-Being in Young Adults

Over 500 million people interact daily with Facebook. Yet, whether Facebook use influences subjective well-being over time is unknown. We addressed this issue using experience-sampling, the most reliable method for measuring in-vivo behavior and psychological experience. We text-messaged people five times per day for two-weeks to examine how Facebook use influences the two components of subjective well-being: how people feel moment-to-moment and how satisfied they are with their lives. Our results indicate that Facebook use predicts negative shifts on both of these variables over time. The more people used Facebook at one time point, the worse they felt the next time we text-messaged them; the more they used Facebook over two-weeks, the more their life satisfaction levels declined over time. Interacting with other people “directly” did not predict these negative outcomes. They were also not moderated by the size of people''s Facebook networks, their perceived supportiveness, motivation for using Facebook, gender, loneliness, self-esteem, or depression. On the surface, Facebook provides an invaluable resource for fulfilling the basic human need for social connection. Rather than enhancing well-being, however, these findings suggest that Facebook may undermine it.     

Chronotype differences in suicidal behavior and impulsivity among suicide attempters

Morning- and evening-type individuals differ on a number of psychological and biological variables. There has been increasing interest in the relationship between chronotype and personality traits. The aim of this study was to investigate the relationship between impulsivity and chronotype in suicide attempters. Eighty-nine suicide attempters were included in the study, and systematic information on suicide attempts was recorded. The Morningness-Eveningness Questionnaire was applied to determine chronotype, and attempter impulsivity was measured by the total score of the Barratt Impulsiveness Scale. Significant differences between chronotype and impulsivity scores were found. Evening-type subjects reported significantly higher impulsivity scores than both neither- and morning-types. A significant association between chronotype and type of suicide attempt was detected. The largest proportion of violent suicide attempters were evening-type subjects. Violent suicide attempters also reported significantly higher impulsivity scores than nonviolent attempters. Previous studies have pointed out possible relations between eveningness and impulsivity. Current findings suggest that eveningness may be a risk factor for violent suicide attempts by increasing impulsivity.     

Is self-reported morbidity related to the circadian clock?

Morningness and eveningness preference, an endogenous component of the circadian clock, is characterized by an interindividual difference in circadian phase and requires of humans a specific timing of behavior. The biological rhythms of morning and evening types are consequently phase shifted with fixed socioeconomic constraints. The impact of this phase shift on health is widely debated. The purpose of the authors' study was to determine the influence of morningness/eveningness preference on self-reported morbidity and health in an active population. A total of 1165 nonshift workers of the French national electrical and gas company, enrolled in the GAZEL cohort and aged 51.3+/-3.3 years, were included in this study. They replied by mail with a completed questionnaire, including morningness/eveningness preference, self-reported morbidity, subjective sleep patterns, and daytime somnolence and sleeping schedules for 3 weeks, during the spring of 1997. Annual self-reported health impairments were assessed with the annual general questionnaire of the GAZEL cohort for 1997. After adjustment for age, sex, and occupational status, morningness-like and eveningness-like participants reported a specific worse self-reported morbidity. Whereas morningness was associated with worse sleep (p = 0.0001), eveningness was associated with feeling less energetic (p = 0.04) and physical mobility (p = 0.02). These relationships were observed even in good sleepers, except for physical mobility. After adjustment for confounding variables, eveningness-like participants reported more sleep (p = 0.0004) and mood (p = 0.00018) disorders than morningness-like participants. Morningness/eveningness preference was related to specific chronic complaints of insomnia: morningness was related with difficulty in maintaining sleep (p = 0.0005) and the impossibility to return to sleep in the early morning (p = 0.0001) (sleep phase-advance syndrome); eveningness was related to difficulty in initiating sleep (p = 0.0001) and morning sleepiness (p = 0.0001). In good sleepers, morningness was related with sleep phase-advance syndrome (p = 0.0001) and eveningness with morning sleepiness (p = 0.0001). In conclusion, the expression (phase advance or delay) of the circadian clock could be related to worse self-reported morbidity and health. These findings must be verified by further epidemiological studies, but they suggest that the impossibility to return to sleep in the early morning is not only associated with age.     

Chronotype and depressive symptoms in students: An investigation of possible mechanisms

ABSTRACT

Individuals with an evening chronotype are at increased risk of experiencing emotional problems, including depressive symptoms. However, the mechanisms underlying these associations remain unclear. The present study aimed to determine whether poor sleep quality, substance use and cognitive emotion regulation difficulties – which have been implicated in the etiology of depression – mediate the relationship between chronotype and depressive symptoms in a student sample, which was assessed cross-sectionally and after 1 year. A total of 742 Dutch students (75% women, mean age 21.4 ± 2.9 years) completed the Quick Inventory of Depressive Symptomatology, the Morningness-Eveningness Questionnaire, the Pittsburgh Sleep Quality Index, a questionnaire assessing alcohol, caffeine, tobacco and cannabis use, the Cognitive Emotion Regulation Questionnaire and the Behavioral Inhibition/Activation Scale. A subsample (n = 115) was assessed 1 year later with the same questionnaires. Cross-sectional analyses showed that evening chronotype was associated with more depressive symptoms, adjusted for age and gender (β = ?0.082, p = 0.028). The relationship between eveningness and depressive symptoms was mediated by sleep quality, alcohol consumption and the cognitive emotion regulation strategies of self-blame and positive reappraisal. In longitudinal analyses, eveningness at baseline predicted more depressive symptoms at follow-up, adjusted for age and gender (β = ?0.29, p = 0.002); after additional adjustment for baseline depressive symptoms, chronotype remained a significant predictor of depressive symptoms at T2 (β = ?0.16, t = ?2.01, p = 0.047). Only poor sleep quality at follow-up was a significant mediator of this relationship. Even though the effect is small in terms of explained variance, eveningness is related to depressive symptoms and this relationship is mediated by poor sleep quality, also in a prospective design. Self-blame and reduced positive reappraisal are correlated with eveningness. Further research is needed to assess the efficacy of chronotherapeutic interventions for the prevention of depression, in addition to sleep education and cognitive approaches.     

The effects of biological rhythms and sleep quality on benign paroxysmal positional vertigo and reflux symptom severity

Recently, there has been increased interest in chronotypes and clinical differences between them. However, there is limited information about the potential influence of the chronotypes on clinical manifestations and symptom intensity of somatic diseases. The aim of this study is to evaluate the impact of biological rhythm differences and sleep quality on benign paroxysmal positional vertigo (BPPV) and larengo pharyngeal reflux (LPR) severity. Forty-four LPR patients, 43 BBPV patients and 42 controls were included in the study. The morningness–eveningness questionnaire was used to determine chronotypes, and the Pittsburgh Sleep Quality Index was used to assess subjective sleep quality. Both patient groups reported a significantly greater tendency to eveningness diurnal preferences compared to healthy controls. As with the circadian preferences, patients with BPPV or LPR characterized by poorer sleep quality and worse insomnia than non-patient individuals. It can be concluded that the circadian rhythm and sleep quality are related to the severity of LPR and BPPV.     

Associations between chronotype,sleep disturbances and seasonality with fatigue and inflammatory bowel disease symptoms

Growing number of studies suggests link between circadian rhythms and inflammatory bowel diseases (IBD) manifestation. We hypothesize that: 1) IBD are associated with increased eveningness and sleep disturbances; 2) eveningness and sleep disturbances are related to more severe IBD symptoms. In total, 129 participants were enrolled to this study, divided into three groups: 34 Crohn’s disease (CD) patients, 38 ulcerative colitis (UC) patients and 57 healthy controls (HC) group. They all fulfilled a questionnaire, consisting of the Composite Scale of Morningness (CSM), Seasonal Pattern Assessment Questionnaire (SPAQ), Pittsburgh Sleep Quality Index, Inflammatory Bowel Disease Questionnaire (IBDQ) and Multidimensional Fatigue Inventory (MFI). Multiple regression models controlled for age and sex revealed that in CD group higher eveningness measured with CSM was associated with higher general fatigue, physical fatigue, mental fatigue and reduced motivation measured by MFI. Lower CSM morning affect is associated with greater general fatigue, physical fatigue and more reduced activity. Greater seasonality scores are associated with increased physical fatigue and more reduced activity and motivation. Lower sleep quality measured with PSQI is associated with higher physical fatigue and more reduced activity. Correlational analysis revealed that higher seasonality and lower sleep quality are associated with increased systemic and bowel symptoms and decreased emotional and social functions measured with IBDQ. In UC group, eveningness is associated with greater general fatigue, physical fatigue and more reduced activity. Higher CSM morning affect is associated with decreased general fatigue, physical fatigue and less reduced activity. Higher CSM circadian preference scores are associated with decreased general and physical fatigue, and less reduced activity. Increased seasonality is associated with more physical fatigue. Lower sleep quality is associated with greater general and physical fatigue. To our best knowledge this is the first study evaluating associations between chronotype and sleep disturbances with IBD symptoms. We have found that chronotype preferences, whose role in IBD has been until now overlooked, may be one of the important factors contributing to fatigue in this clinical group.     

Chronotype and its relationship with sleep disorders in children with attention deficit hyperactivity disorder

Chronotype can be classified as morningness types, people who prefer morning hours for their physical and mental activities; eveningness types, people who prefer the afternoon or evening hours; and intermediate types, those who show characteristics of both morningness and eveningness types. Attention deficit hyperactivity disorder (ADHD) has been linked with disturbances in chronotype, particularly increased eveningness. Despite the possibility of an association between chronotypes, sleep disturbances and ADHD symptoms, there is little evidence of this association considering the child population. The purpose of this study was to examine chronotype preferences in children aged between 7 and 12 years who were diagnosed as having ADHD in the context of sleep disturbances. The Schedule for Affective Disorders and Schizophrenia for School Age Children-Present and Lifetime Version, Conner’s Rating Scales, Children’s Sleep Habit Questionnaire and Children’s Chronotype Questionnaire were used for the evaluation of children with ADHD and healthy controls. The ADHD group was 73% combined-type, and the eveningness scores of the ADHD group (n = 52) were significantly higher than the control group (n = 52) (p < 0.01). There was a positive correlation between the higher scores of eveningness and total scores on resistance to sleep time (p < 0.09), respiratory problems during sleep and daytime sleepiness in the ADHD group. CSHQ total score was found to be a predictive factor for eveningness among children with ADHD (p < 0.01). These findings highlight possible reciprocal links between ADHD symptoms, sleep disturbances and chronotype in children aged 7–12 years, which might lead to individualized treatment options.     

Morningness/Eveningness and Satisfaction With Life in a Polish Sample

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 magnitude and direction of association between morningness/eveningness and satisfaction with life could be independent of culture or geographical location. (Author correspondence: E-mail: konrad.jankowski@psych.uw.edu.pl)     

Morningness-eveningness and seasonality

The study aimed to elucidate previously observed associations between morningness–eveningness and seasonality by analysing their distinct aspects separately: morning affect (MA) and time-of-day preference, different seasonal types and patterns (winter, summer, etc.), the degree of seasonality and perceived negative impact of seasonality. Students from Warsaw (N = 522) completed the Seasonal Pattern Assessment Questionnaire and the Composite Scale of Morningness. Winter seasonality was related to lower MA, but unrelated to time-of-day preference. Global seasonality score was negatively associated with MA in winter seasonality, but not in other seasonality patterns, and unrelated to time-of-day preference. These associations remained significant after controlling for sex, age and season of assessment. It is concluded that winter seasonality is related to low MA, but not to time-of-day preference. The above results indicate that MA can be considered as an all year round indicator of proneness to winter seasonality and eventually to seasonal affective disorder. The results also suggest that MA and time-of-day preference should be analysed separately in future research on morningness–eveningness.     

A twin-study of genetic contributions to morningness–eveningness and depression

Circadian rhythms are associated with the preference for sleep–wake timing, also known as morningness–eveningness (ME). Both circadian rhythms and ME are influenced by genetic factors. Studies show an association between eveningness and depression. This study investigates the heritability of ME and whether ME and depression share common genetic influences. Study participants (n?=?1237) were from the Vietnam Era Twin Study of Aging, a longitudinal study of aging with a baseline in midlife. Participants received the Morningness–Eveningness Questionnaire (MEQ) and the Center for Epidemiologic Studies Depression (CES-D) Scale as part of an extensive neurocognitive and psychosocial assessment. MEQ correlations between members of twin pairs were 0.41 (95% CI 0.31–0.49) for monozygotic (MZ) twins and 0.28 for dizygotic (DZ) twins (95% CI 0.19–0.41). CES-D correlations were 0.38 (95% CI 0.28–0.46) for MZ twins and 0.24 (95% CI 0.14–0.36) for DZ twins. Greater eveningness (i.e. lower MEQ scores) was significantly related to more depression symptoms (phenotypic correlation?=??0.15 (95% CI ?0.21 to ?0.09). In the best fitting model, the heritability estimates are 0.42 for the MEQ and 0.37 for the CES-D. A significant genetic correlation of ?0.21 indicated that ME and depression share a significant amount of their underlying genetic variance. The genetic covariance between ME and depression accounted for 59.1% of the phenotypic correlation. Of the CES-D sub-scales, Depressed Mood and Interpersonal Difficulties were significantly heritable, while only Well-Being had a significant genetic correlation with ME. ME and depression are both heritable (ME 0.42, depression 0.37) and share common genetic factors, suggesting an overlap in etiology and the relevance of circadian rhythms to depression. Further study of this relationship may help elucidate etiological factors in depression and targets for treatment.