The Chinese Morningness-Eveningness-Stability-Scale improved (MESSi): validity,reliability, and associations with sleep quality,personality, affect and life satisfaction

ABSTRACT

Individual differences in time of day preference have important correlates. Morningness is associated with greater well-being, while eveningness is associated with more maladaptive behaviors, psychological distress, and disorder. The availability of valid, reliable, questionnaire scales is central to this ongoing research. The recently developed Morningness–Eveningness-Stability-Scale improved (MESSi) utilizes items from previously established scales to assess the dimensions of Morning Affect (MA), Eveningness (EV), and amplitude of diurnal variation/distinctness (DI). The current study developed a Chinese version of the MESSi scale. A sample of 767 Chinese university students completed the translated MESSi, the reduced Morningness-Eveningness Questionnaire (rMEQ), and scales assessing sleep quality, positive and negative affect, the big five personality dimensions, and life satisfaction. An independent sample of 80 undergraduates completed the MESSi twice over a 14–19 day period. Exploratory and confirmatory factor analysis both supported the original three-factor structure of the MESSi, with the subscales of MA, EV, and DI. Internal consistency and test–retest reliability were acceptable/good, and expected correlations with other measures were found, including: MA correlated positively with the rMEQ, conscientiousness, positive affect, and life satisfaction; EV correlated negatively with rMEQ and conscientiousness; DI correlated positively with poor sleep quality, negative affect, and neuroticism. Overall, the results support the validity and reliability of the Chinese version of the MESSi.     

Adaptation of the Morningness–Eveningness Stability Scale improved (MESSi) into Turkish

Morningness–eveningness is an individual difference that is related with various traits such as behavioral problems, personality, and health. The aim of the current study is to adopt the Morningness–Eveningness Stability Scale improved (MESSi) which is a novel assessment tool that consists of subscales of morning affect (MA), eveningness (EV), and distinctness (DI) into Turkish. Concurrent validity of the MESSi along with Big five inventory (BIG-5), Subjective alertness level, Pittsburg Sleep Quality Index (PSQI), Positive and Negative Affect Schedule (PANAS) were analyzed. The scale was administered to 1,076 high school and university students aged 14–47 years (M = 19.49, SD = 3.53). The explanatory factor analysis (EFA) and confirmatory factor analysis (CFA) revealed the three-factor structure of MESSi. According to the concurrent validity result of the MESSi with BIG-5, conscientiousness was found to correlate positively with MA and negatively with EV. Also, extraversion showed a negative correlation with DI and positive correlation with MA. Furthermore, the subjective alertness rating results showed that MA was positively related to alertness in the morning hours and negatively in the evening hours. Also, sleep quality-related results showed that EV and DI are positively related to total PSQI scores and negatively related to MA. In addition, concerning positive affect (PA) and negative affect (NA), MA was positively related with PA and negatively with NA, while DI was negatively related with PA and positively with NA. In overall, MESSi is a valid and reliable instrument and can be used in Turkish students.     

Preliminary findings for the validity of the Morningness–Eveningness-Stability Scale improved (MESSi): Correlations with activity levels and personality

Aim of the present study is an additional validation of the Morningness–Eveningness-Stability Scale improved (MESSi). We screened a total of 97 German students using the reduced Morningness–Eveningness Questionnaire (rMEQ) to identify a subsample (N = 42) of definite morning and evening types (31% males, mean age: 24.8 ± 5.8?years). The participants provided information about their sleep–wake rhythm (diary), personality traits (questionnaire) and experienced actigraphic monitoring. Correlations of the MESSi components “Morning affect subscale” (MA) (r = 0.91, p < 0.01) and “Eveningness subscale” (r = ?0.87, p < 0.01) with the rMEQ showed good convergent validity. MA was also significantly negatively correlated with the acrophase and the midpoint of sleep as measured by actigraphy.     

Sleep habits,circadian preferences and substance use in a Mexican population: the use of the Morningness-Eveningness-Stability-Scale improved (MESSi)

ABSTRACT

This study aimed to validate the Morningness-Eveningness-Stability-Scale improved (MESSi) in Mexico, analyzing the factor structure and sleep habits, combined with the proposal of cutoff values for the scales, and to assess the relationship with substance use. We applied the questionnaires through an online survey to a total sample of 510 Mexicans, aged 18–77 years (M = 27.79, SD = 10.24). The MESSi showed an acceptable fit and the Cronbach’s alpha coefficients were good to satisfactory in the Mexican sample in every subscale: Morning Affect (MA, α = 0.90), Eveningness (EV, α = 0.88), Distinctness (DI, α = 0.80). In order to obtain a better interpretation of the MESSi subscales, we decided to propose cutoff points corresponding to the 25th–75th percentile. The categories were depicted as strong trait presence, intermediate trait presence and weak trait presence. When applying the cutoff points for the MESSi sub-scales, with Morning Affect (MA), strong-types went to bed and woke up earlier and had more sleep than weak-types during weekdays and weekends and reported less social jetlag. For Eveningness (EV), strong-types went to bed and woke up later than weak-types on weekdays and weekends. Also, strong-types had a shorter time in bed during weekdays but not on weekends and reported more social jetlag. Lastly, with Distinctness (DI), the results reported that those with a strong-type showed greater amplitude on weekdays and weekends. Furthermore, the MESSi scale found that evening people consumed more alcohol and tobacco. Our study supported the validity and reliability of the MESSi in a Mexican population and the relationship between eveningness and substance consumption. Furthermore, the proposed cutoff scores for the MESSi sub-scales add a novel approach for the measurement and interpretation of the scale.     

Cross-cultural validity of Morningness-Eveningness Stability Scale improved (MESSi) in Iran,Spain and Germany

Morningness-Eveningness Stability Scale improved (MESSi) is a newly constructed measure to assess circadian types and amplitude. In this study, we applied this measure to participants from three different countries: Germany, Spain and Iran. Confirmatory factorial analysis (CFA) of MESSi displayed mediocre fit in the three countries. Comparing increasingly stringent models using multigroup confirmatory factor analyses indicated at least partial measurement invariance (metric invariance) by country for Morning Affect and Distinctness subscales. Age was positively related to Morning Affect (MA), and negatively related to Eveningness (EV) and Distinctness (DI). Men reported higher MA than women, whereas women reported higher DI than men. Regarding country effect, Iranian participants reported highest MA compared to Spaniards and Germans, whereas Germans reported higher DI compared to Iranians and Spaniards. As a conclusion, our study corroborated the validity and reliability of MESSi across three different countries with different geographical and cultural characteristics.     

Circadian preference and decision-making styles

The present study aimed to explore for the first time the relationship between circadian preference and different decision-making styles. In total, 501 young adults (330 females), with a mean age of 21.07 ± 1.99 years, took part in the study. The participants completed the reduced version of the morningness–eveningness questionnaire (rMEQ) and the general decision-making style inventory (GDMS). The rMEQ enabled to assess the circadian preference, with lower rMEQ scores pointing toward eveningness preference. The GDMS measured five decision-making styles: rational, intuitive, dependent, avoidant and spontaneous. Higher scores on each GDMS decision-making style reflect a higher prevalence of the corresponding style. A set of multiple regression analyses was performed with rMEQ score, gender and age as predictors together with each GDMS decision-making style as dependent variable. rMEQ score proved to be the only significant (negative) predictor of avoidant and spontaneous decision-making styles, i.e. lower rMEQ score (tendency toward eveningness) significantly predicted higher score at these decision-making styles. The present results suggest that eveningness preference is significantly related to avoidant and spontaneous decision-making styles in young adults. Such results will be discussed with reference to the effects of decision-making styles on decision-making in different types of workers and mental health.     

The reduced Morningness–Eveningness Questionnaire: Psychometric properties and related factors in a young Swedish population

During puberty, there is a delay in sleep patterns and the circadian clock, and the prevalence of sleep difficulties is high among young adults. Thus, it is important to be able to measure chronotype (CT) in this group, both in the clinic and for broader epidemiological studies, to better understand the sleep difficulties observed. The reduced version of one of the most widely used questionnaire to measure CT, the Horne & Östberg Morningness–Eveningness Questionnaire (MEQ), has been developed and validated in many languages. The aim of the present study was to investigate the reliability and validity of the Swedish reduced MEQ (rMEQ) and to investigate factors correlated with rMEQ scores in a random sample of young Swedish participants. We sent the rMEQ, sleep questions, demographic questions, the Insomnia Severity Index (ISI), the Epworth Sleepiness Scale, and the Hospital Anxiety and Depression Scale (HADS-A and HADS-D) to 1000 randomly selected individuals aged 16–26 years in Uppsala, Sweden (response rate = 68%). A parallel analysis of the rMEQ revealed a single factor solution. Inter-item correlations within the questionnaire were between 0.08 and 0.46. One of the rMEQ items displayed weak correlations with the other questions. Cronbach’s alpha of the rMEQ was 0.68. Low rMEQ scores (eveningness) were correlated with more frequent late bedtimes and difficulties getting up in the morning. Lower rMEQ scores were significantly related to male sex, no educational activity or work, nicotine use, younger age, and higher ISI and HADS-D scores. Even though the inter-item correlations of the rMEQ were very low to moderate, the rMEQ had a Cronbach’s alpha not far off from acceptable levels, and the strong correlations of the rMEQ scores with responses to the sleep questions indicated that the rMEQ had an adequate validity. To conclude, the rMEQ can be used to effectively estimate CT when a short questionnaire is required; however, caution should be taken when interpreting the results considering the reliability of the questionnaire.     

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.     

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.     

Psychometric properties of the Russian version of the Composite Scale of Morningness

Morningness–eveningness preference is commonly measured by questionnaires, such as the Composite Scale of Morningness (CSM). Purpose of our study was to assess the Russian translation of the CSM and provide psychometric properties of this scale. Participants (N = 406) were students from high schools and university in Petrozavodsk. Mean age was 20.47 ± 3.66 with a range of 12–38 years. Mean CSM scores were 31.43 ± 6.32, with a range from 14 to 50. Internal reliability, as measured by Cronbach’s α, was 0.823. There was no negative correlation among the items. The reliability of 0.82 is good and fits into previous work done with the CSM in many different countries. The factor structure appears as a two-factor structure based on parallel analysis and a three-factor structure based on the eigenvalue greater than one criterion. We suggest retaining the two-factor structure, one factor could be labelled as morning affect and the other one as self-assessment/activity planning. Construct validity was checked with the MCTQ and showed that the correlations between midpoint of sleep and CSM are comparable to other studies.     

Initial psychometric characterization for the Portuguese version of the Morningness-Eveningness-Stability-Scale improved (MESSi)

ABSTRACT

This work reports the initial psychometric characterization of the Morningness-Eveningness-Stability-Scale improved (MESSi) for Portuguese young-adults (N = 466). A confirmatory factor analysis confirmed a three-factor model (i.e. Morning Affect, Eveningness and Distinctness) in our data, as originally proposed. Furthermore, construct validity evidence in relation to external variables (i.e. morningness/eveningness and satisfaction with life), as well as adequate reliability (i.e. internal consistency and test-retest reliability), were found. Finally, sex-based invariance and between-sex differences were investigated for the three subscales, as were correlations with age. Results point to the suitability of the MESSi for multi-cultural research on relevant and multiple aspects of chronotype.     

Advanced phases and reduced amplitudes are suggested to characterize the daily rest-activity cycles in depressed adolescent boys

Self-reported eveningness has been previously associated with depressed mood among adults and adolescents. Here, we study how circadian indicators based on actigraphic data differ between depressed and healthy adolescent boys. Our sample consisted of 17 medication-free adolescent boys, aged 14.5 to 17.5 years, of which eight had depressive disorder and were currently depressed and nine were healthy comparison participants. Psychiatric assessment was conducted by diagnostic interviews and complemented with observer-rating and self-rating scales. Actigraphic data were collected with wrist actigraphs for a minimum period of 25 consecutive days (range of 25 to 44 days). The behavioral trait of morningness–eveningness was measured with the 19-item Horne-Östberg Morningness–Eveningness Questionnaire. Based on the self-report, the depressed boys were more prone to eveningness than healthy controls, but based on the actigraphic data, they had earlier phases especially on school days and lower activity levels especially on weekends. On weekends, the depressed boys showed a greater shift toward later-timed phases than healthy controls. Our results confirm a mismatch of the subjective morningness–eveningness preference (late-preference) and the objective rest-activity rhythm (early-prone) during school days in depressed adolescent boys.     

Morningness–eveningness and sleep habits at school: a comparative study between Mexico and Spain

Morningness–eveningness and sleep habits relationship were studied between Mexican and Spanish adolescents. A total sample of 611 Mexican and Spanish adolescents (13–15 years old; 14.12 ± 0.75) participated in this comparative study and filled out the preferred timing of sleep and activity using item 19 of Morningness–Eveningness Questionnaire and reported sleep habits from open questions about typical bed and rise times during the weekdays and weekends. Spanish adolescents reported differences in sleep habits according to sex and chronotype, whereas Mexican adolescents only reported differences regarding chronotype on weekends. When country effect was analyzed, the most relevant result was the short sleep length on weekdays of Mexican adolescents (7:11 vs. 8:05), who reported earlier weekday rise time (6:11 vs. 7:15) but similar weekday bedtime (23:00 vs. 23:09) compared to Spanish adolescents. Sleep habits among Mexicans seem more influenced by a social factor related to school schedule than environmental factor related to latitude.     

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.     

Discrimination between extreme chronotypes using the full and reduced version of the Morningness-Eveningness Questionnaire

The aim of this study was to carry out a comparison of the ability to discriminate between extreme chronotypes, i.e., morning- and evening-types, among the Morningness-Eveningness Questionnaire (MEQ) and its reduced version (rMEQ). To this end a secondary analysis of cohort studies, using two different approaches, was carried out. The first, subjective, relied on the computing of overlap between extreme chronotypes according to their hourly ideal bedtime, get-up time and midpoint of sleep reported at the MEQ and rMEQ, while the second, objective, on the corresponding actual-actigraphic times. At the subjective approach, 2706 participants filled in the MEQ, while 940 the rMEQ (age range of both groups: 18–30 years). The overlap was significantly lower among those who filled the rMEQ than MEQ when considering ideal midpoint of sleep (13.70% and 46.28%, respectively) and get-up time (47.04% and 62.34%, respectively). At the objective approach, 51 participants filled in the MEQ while 52 the rMEQ (age range: 19–30 years in both groups) at the end of one week of actigraphic recording. No significantly different overlap across those who filled the MEQ or rMEQ was observed with reference to the examined actigraphic times. Results of subjective assessment showed as rMEQ more clearly discriminated between extreme chronotypes than MEQ. The attempt to find an objective confirmation did not provide the same results, probably as a consequence of a masking effect by social rhythms.     

Morningness–eveningness and amplitude – development and validation of an improved composite scale to measure circadian preference and stability (MESSi)

Measuring morningness–eveningness is an important aspect of individual differences because it is associated with many aspects of personality and health. The present study outlines recent advancements in the field of measurement and proposes an improved assessment of morningness–eveningness, such as the measurement of circadian amplitude, updating and reflecting new item developments, addressing the clock time based measures, the morning-biased items and the aspect of uni versus multidimensionality. Four studies have been carried out in Germany to present a novel development (with a total sample of N = 1181). In study I, the exploratory factor analysis (EFA) revealed three dimensions, one of morningness, one of eveningness and one of amplitude/stability. Then, items were reduced to present a clearer factor structure by removing ambiguous items. In the second study, a shortened questionnaire was applied, with 15 items (5 per construct), but Confirmatory Factor Analysis (CFA) did not provide acceptable fit indices. Refining items were made in study III, which again showed a clearer factor structure in EFA, and subsequently, in study IV, the refined set of 15 items provided a good fit of a CFA. The final questionnaire was tested for validity by applying clock times, personality questions and alertness ratings. Thus, this newly developed questionnaire contains three distinct dimensions. To reflect the new content, the scale is labelled morningness–eveningness-stability-scale improved (MESSi).     

Premature birth and circadian preference in young adulthood: evidence from two birth cohorts

A preference for eveningness (being a “night owl”) and preterm birth (<37 weeks of gestation) are associated with similar adversities, such as elevated blood pressure, impaired glucose regulation, poorer physical fitness, and lower mood. Yet, it remains unclear if and how preterm birth is associated with circadian preference. The aim of this study was to assess this association across the whole gestation range, using both objective and subjective measurements of circadian preference.

Circadian preference was measured among 594 young adults (mean age 24.3 years, SD 1.3) from two cohorts: the ESTER study and the Arvo Ylppö Longitudinal Study. We compared 83 participants born early preterm (<34 weeks) and 165 late preterm (34 to <37 weeks) with those born at term (≥37 weeks, n = 346). We also compared very low birth weight (VLBW, <1500 g) participants with term-born controls. We obtained objective sleep data with actigraphs that were worn for a mean period of 6.8 (SD 1.4) nights. Our primary outcome was sleep midpoint during weekdays and weekend. The sleep midpoint is the half-way time between falling asleep and waking up, and it represents sleep timing. We also investigated subjective chronotype with the Morningness–Eveningness Questionnaire (MEQ) in 688 (n = 138/221/329) ESTER participants. The MEQ consists of 19 questions, which estimates the respondent to be of a “morning”, “evening,” or “intermediate” chronotype, based on the Morningness–Eveningness Score (MES). We analyzed the data from the actigraphs and the MES with three linear regression models, and analyzed distribution of the chronotype class with Pearson χ2.

There were no consistent differences across the study groups in sleep midpoint. As compared with those born at term, the mean differences in minutes:seconds and 95% confidence intervals for the sleep midpoint were: early preterm weekdays 11:47 (?8:34 to 32:08), early preterm weekend 4:14 (?19:45 to 28:13), late preterm weekdays ?10:28 (?26:16 to 5:21), and late preterm weekend ?1:29 (?20:36 to 17:37). There was no difference in sleep timing between VLBW-participants and controls either. The distribution of chronotype in the MEQ among all participants was 12.4% morningness, 65.4% intermediate, and 22.2% eveningness. The distribution of the subjective chronotype class did not differ between the three gestational age groups (p = 0.98). The linear regression models did not show any influence of gestational age group or VLBW status on the MES (all p > 0.5).

We found no consistent differences between adults born early or late preterm and those born at term in circadian preference. The earlier circadian preference previously observed in those born smallest is unlikely to extend across the whole range of preterm birth.     

School start times matter,eveningness does not

ABSTRACT

Morningness–Eveningness (M–E) has been associated with school performance when school activities are arranged early in the morning. This study aims to evaluate this association in 224 adolescents of a secondary school in Montevideo, Uruguay, attending either morning or afternoon shifts. Students’ socio-demographic characteristics and performance indicators were similar across shifts, while afternoon-shift students exhibited later circadian preferences. After controlling for socio-demographic and other educational variables, eveningness was associated with lower grades only in morning-shift students. Our study suggests that eveningness influence on school performance is contingent on the temporal arrangement of scholar activities.     

Do different circadian typology measures modulate their relationship with personality? A test using the Alternative Five Factor Model

The relationship between personality and circadian typology shows some inconsistent results and it has been hypothesized that the model used to measure personality might have a moderating effect on this relationship. However, it has never been explored if this inconsistency was dependent on the questionnaire used to measure differences in circadian rhythms as well. We explored this issue in a sample of 564 university students (32% men; 19–40 years) using the Zuckerman–Kuhlman Personality Questionnaire, which is based on an evolutionary-biological approach, in combination with the Composite Scale of Morningness (CSM) and the reduced Morningness–Eveningness Questionnaire (rMEQ). Both questionnaires detected differences between circadian typologies in Sociability (highest in evening types; ET) and Impulsive Sensation-Seeking scales (highest in ET), while the CSM also detected differences in Activity (lowest in ET) and Aggression-Hostility (highest in ET). Further, both questionnaires detected differences between circadian typologies in the subscales General Activity (morning types [MT] higher than ET), Impulsivity (ET highest) and Sensation-Seeking (highest in ET). Differences between circadian typologies/groups in the subscales Parties (highest in ET) and Isolation Intolerance (lowest in MT) were only detected by the rMEQ. The CSM clearly separated evening types from neither and morning types while the rMEQ showed that neither types are not intermediate but closer to evening types in General Activity and Isolation Intolerance, and closer to morning types in Impulsive Sensation-Seeking, Parties, Impulsivity and Sensation Seeking. The obtained results indicate that the relationship between circadian typology and personality may be dependent on the instrument used to assess circadian typology. This fact may help to explain some of the conflicting data available on the relationship between these two concepts.     

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.