Morningness or Morning Affect? A Short Composite Scale of Morningness

Nonlinear associations between insomnia symptoms and circadian preferences in the general population: Symptom-specific and lifespan differences in men and women

OBJECTIVES

This study investigated (non)linear associations between different eveningness characteristics (bedtime, wake time, morning affect, and peak performance time) and insomnia symptoms (difficulties initiating sleep, difficulties maintaining sleep, and nonrestorative sleep) in a large general population sample.

METHODS

The data came from digital surveys about insomnia (Minimal Insomnia Scale) and circadian preferences (Children's Chronotype Questionnaire/Composite Scale of Morningness) completed by the Dutch general population (37,389 participants aged 4-91years, 42.4% men) in the Lifelines cohort substudy Comorbid Conditions of ADHD.

RESULTS

Using generalized additive modeling, we found that different characteristics of eveningness related to insomnia either exponentially (later wake time/peak performance time, worse morning affect) or quadratically (early and late bedtime/midpoint of sleep). While difficulties initiating sleep and nonrestorative sleep were strongly associated with all eveningness characteristics, difficulties maintaining sleep related only to earlier bedtimes. These relationships were similar for men and women but varied partly in shapes and strengths across the lifespan. Additional analyses showed that bedtime and wake time were associated with insomnia symptoms only when their combination would result in an unusually long or short preferred time in bed.

CONCLUSION

The association between eveningness and insomnia symptoms highly depends on whether eveningness is reflected by daytime performance or sleep-wake time. The pattern and strength of these associations also vary depending on age and insomnia symptom, but less so on sex. Future sleep-related research and policies relying on circadian preferences should account for the nonlinearity, dimension/symptom-related specificity and age-related differences in the association between eveningness and insomnia symptoms.

Evidence for environment hypothesis: Cross-cultural measurement invariance of the composite scale of morningness across Bangladesh and Spain

Morningness-eveningness reflects individual differences in circadian functioning and is related to health and well-being. Cross-cultural comparison could facilitate understanding of the environmental factors affecting morningness-eveningness, which requires establishing cross-cultural validity of the relevant assessment tools. In this study, we applied the Composite Scale of Morningness (CSM) to Bangladeshi (n = 1015; 37.9% women) and Spanish (n = 1054; 73.2% women) university students (aged 18-27 years) to evaluate alternative factorial models of the CSM and to test its measurement invariance across cultures. Moreover, this study tested environment hypothesis, suggesting that higher average temperatures and lower latitudes would be related to greater morningness. From nine competing factorial models, a bifactor model with two specific factors (morning preference and morning affect) showed the best fit for both cultures. The two-factor bifactor model had full metric invariance with partial scalar and strict invariance across cultures. The Bangladesh-Spain comparison of the CSM scores revealed higher morningness in Bangladeshi students which supports the environment hypothesis. Overall, this research confirms that morningness-eveningness construct is perceived and interpreted similarly by the Bangladeshi and Spanish students. Importantly, this study highlights the effects of environmental factors including latitude and temperature on morningness-eveningness, and thus facilitates further cross-cultural morningness-eveningness research.

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

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

Morning affect or sleep inertia? Comparing the constructs and their measurement

The construct of Morning Affect (MA; alertness upon awakening/time required to feel fully awake) emerged from exploratory factor analysis of morningness-eveningness questionnaires, and while it has been equated with morningness-eveningness preference it has much conceptual overlap with sleep inertia (SI; the transitional state between sleep and being fully awake). The current study compared questionnaire measures of these constructs to help clarify their inter-relationships. A volunteer sample of 453 students at an English-medium university in China completed an online survey including the Sleep Inertia Questionnaire (SIQ), the Morningness-Eveningness-Stability-Scale-improved (MESSi), with subscales for MA, Eveningness, and Distinctness (amplitude of diurnal variation), and the reduced Morningness-Eveningness Questionnaire (rMEQ). Measures of depression, sleep quality, mindfulness, and personality were also included. Exploratory factor analysis of the SIQ, MESSi, and rMEQ items revealed seven factors: Cognitive, Emotional, and Physiological SI, Responses to SI (including one MA item), and Duration of SI (one SIQ item, 3/5 MA items, and one rMEQ item); Morningness-Eveningness (MESSi Eveningness items, plus 3/5 rMEQ items); Distinctness (3/5 MESSi items). These results suggest that Morning Affect may be better characterised as a general measure of sleep inertia, and may contribute to ongoing development/refinement of questionnaire measures of circadian functioning.

Assessment of the spectrum of depression and bipolarity in patients with type 1 diabetes

AIMS

The aim of the study was to check the prevalence of unipolarity (depression), bipolarity, as well as the quality of sleep and temperament traits in patients with type 1 diabetes (T1DM) who are provided with optimal conditions of diabetes care and to identify possible risk factors connected with affective traits.

MATERIALS AND METHODS

Out of the 107 T1DM patients, 78 (54 females, 24 males) were included for the analysis (HbA1c [%] 7.11 ± 1.0, BMI [kg/m² ] 25.3 ± 5.6; Years of disease duration [N] 13.7 ± 8.3). The patients filled in a set of questionnaires during their regular visit to the outpatient clinic. Three patients from the whole group were on intensive insulin therapy with Multiple Daily Injections (MDI) and Self-Monitoring of Blood Glucose (SMBG), all the rest were on various types of personal insulin pumps (years on insulin pump [N] 9.1 ± 4.5). All the patients were on regular diabetologist care, with regular visits in a Centre for Advanced Technologies in Diabetes (at least every 6 months).

RESULTS

In QIDS-S (full explanation and abbreviation 26 patients (33.8%) were screened positive for depression, in PHQ (full explanation and ab 57.7% of the patients (45 patients) had symptoms of depression (age was negatively correlated with PHQ score [r = -0.26; p = 0.023]). In CES-D 16 (20%) of the patients assessed their present affect as depressed. None of the analysed clinical variables correlated with depression scores. In the Mood Disorder Questionnaire (MDQ), 16 patients reported having symptoms of bipolarity (20.5% vs. 79.5%). Hypomania Checklist (HCL) analysis indicated 10 patients with bipolar traits (>14) (14.9% vs. 85.1%). None of the analysed clinical variables correlated with HCL results. 11.5% of patients were indicated to be of morning type. Morningness was more often seen in younger patients (r = 0.39; p = 0.001). As many as 46.6% declared that they had poor sleep quality. The temperament traits analysis correlated with clinical parameters: Cyclothymic temperament trait was negatively correlated with age (r = -0.30; p = 0.007) and positively with HbA1c level (r = 0.30; p = 0.025). Hyperthymic temperament was positively correlated with (BMI r = 0.28; p = 0.016). Quality of sleep was highly correlated with depressive symptoms CESD (r = 0.61, p = 0.001), PHQ Score (r = 0.62; p = 0.001), QISD (r = 0.68; p = 0.001) and bipolarity MDQ (p = 0.50, p = 0.001) and HCL (r = 0.42, p = 0.001). In addition, QIDS was shown to be correlated with the following features of temperament: depressive factor (r = 0.41; p = 0.001), irritable factor (r = 0.53; p = 0.001), cyclothymic factor (r = 0.59; p = 0.001), anxious factor (r = 0.58, p = 0.001).

CONCLUSIONS

The prevalence of affective disorders and poor sleep quality in the examined T1DM patients was much higher than in the general population. Even if the patients have in general good glycaemic control, their mental health condition should not be neglected. Well organised cooperation between patients, diabetologists, psychiatrists and psychotherapists is needed (Clinical Trials Identifier: NCT04616391).

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

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

Change in circadian preference predicts sustained treatment outcomes in patients with unipolar depression and evening preference

STUDY OBJECTIVES

Eveningness is associated with worse outcomes in depression. It remained unclear if eveningness could be altered with chronobiological therapy and whether such a change would predict long-term outcomes of depression.

METHODS

Data from a randomized controlled trial of 5-week adjunctive bright light therapy with a gradual advance protocol conducted in 91 adult patients with nonseasonal unipolar depression and eveningness (Morningness-Eveningness Questionnaire, score ≤ 41) was examined. "Change of eveningness" was defined by Morningness-Eveningness Questionnaire score over 41 at posttreatment week 5 and "persistent change of eveningness" was defined as maintenance of Morningness-Eveningness Questionnaire score > 41 throughout the follow-up period from week 5 to posttreatment 5 months.

RESULTS

Thirty-three participants (36%) had change of eveningness at week 5. Generalized estimating equations models showed that a change of eveningness at week 5 predicted a 2-fold increase in remission of depression over the 5-month follow up (odds ratio = 2.61 95% confidence interval 1.20-5.71, P = .016). Twenty-five participants (75.7%) had a persistent change and were more likely to achieve a remission of depression over the 5-month follow up (odds ratio = 3.18, 95% confidence interval: 1.35-7.50, P = .008).

CONCLUSIONS

One-third of the patients with depression changed their evening-preference after 5-week of chronotherapeutic treatment, and such change predicted a higher likelihood of depression remission over 5 months of follow-up.

CLINICAL TRIAL REGISTRATION

Registry: Chinese Clinical Trial Registry; Name: Adjunctive light treatment in major depressive disorder patients with evening chronotype-A randomized controlled trial; URL: https://www.chictr.org.cn/showprojen.aspx?proj=11672; Identifier: ChiCTR-IOR-15006937.

CITATION

Chan JWY, Chan NY, Li SX, et al. Change in circadian preference predicts sustained treatment outcomes in patients with unipolar depression and evening preference. J Clin Sleep Med. 2022;18(2):523-531.

More Than Morningness: The Effect of Circadian Rhythm Amplitude and Stability on Resilience, Coping, and Sleep Duration

Self-report tools that measure circadian rhythms have focused primarily on phase. We add to the sparse literature on assessing amplitude and stability. We randomly recruited 1,163 participants who completed several measures. The correlation between the LV scale (amplitude) and FR scale (stability) was -0.12 (p < 0.01). As expected, amplitude was negatively associated with phase (r = -0.64, p < 0.01) while stability showed a weak link with phase (r = 0.07, p < 0.05). Structural equation modeling suggested a close model-fit of the factor structure in the sample (RMSEA = 0.033). The LV scale explained 22% of the variance, while the FR scale explained 23%. Scale reliability was satisfactory for the LV scale (0.68) and good for the FR scale (0.73). Participants with low amplitude or flexible rhythms reported significantly better resilience, coping, and required less daily sleep. We constructed a composite circadian categorical variable to combine the best attributes from the LV and FR scales; participants with both low amplitude and flexible rhythms, reported significantly better resilience, coping, and less sleep need. We found rhythm amplitude decreased with age, while stability remained constant.

The role of chronotype in the interaction between the alerting and the executive control networks

Chronotype refers to the time of day preferred by individuals to perform daily activities according to their circadian rhythm. We asked whether synchrony effects, that is, the difference in performance between the optimal and non-optimal time of day as a function of chronotype, are observed in two tasks that differently involve the endogenous component of the alerting network, the psychomotor visual task (PVT) and the flanker task. From an initial sample of 132 students that filled in the Morningness-Eveningness Questionnaire (MEQ), 18 were classified as Morning-types and 16 as Evening-types. Evening-types showed synchrony effects in both tasks, whereas Morning-types failed to show synchrony effects in the flanker task and when the PVT was first performed at the non-optimal time of day. Thus, Morning-types might have seen increased their vigilant attention at their non-optimal time of day due to the cognitive demands of the flanker task and to the novelty with the PVT. Phasic alerting generated by alerting tones increased conflict score in the flanker task, but time of day did not modulate the congruence effect. Chronotype determines vigilant attention more decisively in Evening-types than in Morning-types individuals. Also, exogenous but not endogenous alerting exerts a deleterious effect on conflict resolution.

Validity and reliability of the Slovene version of the Morningness-Eveningness Questionnaire

Morningness-eveningness (ME) can be defined as individual differences in sleep-wake patterns, and the time of day people feel and perform best. Various self-report instruments that measure ME have been developed. The Horne and Östberg Morningness-Eveningness Questionnaire (MEQ) has most frequently been used for classifying ME types. The aim of this study was to investigate the validity and reliability of the Slovene version of the MEQ (Slovene MEQ). Two hundred and sixty-five participants (65.3% women, 34,7% men, mean age 38,1 years, range 19-67) took the Slovene MEQ twice, 2 weeks apart (MEQ test and retest). Internal consistency of the Slovene MEQ items was high, with Cronbach's Alpha coefficients of 0.86. The test-retest reliability was also high, with intraclass correlation coefficient (ICC) of 0.96. The classification of chronotypes on middle-aged population offered a more balanced representation of the five chronotypes than those proposed by the authors Horne and Östberg . Age changes in chronotype could be confirmed in this study in the supposed direction with older adults being more morning-oriented. The criterion validity of the Slovene MEQ through the relationship of morningness and basic personality traits showed that conscientiousness and agreeableness demonstrated positive and significant correlations with morningness. A low negative correlation was observed between openness and morningness, with higher eveningness among more open participants.

Sleep restriction and testosterone concentrations in young healthy males: randomized controlled studies of acute and chronic short sleep

OBJECTIVE

Low testosterone in men increases the risk for various disorders. Severe sleep restriction (SR) may reduce testosterone, but the effects of long-term short sleep are unknown. This study tested the effects of SR on circulating testosterone in healthy young men.

DESIGN

Randomized controlled studies of SR vs habitual sleep (HS) in inpatient (study 1, n=14) and outpatient (study 2, n=13) settings.

METHODS

Study 1 involved severe, acute SR (4 hours time in bed [TIB]) vs HS (9 hours TIB) for 5 nights; study 2 consisted of mild, long-term SR (HS 1.5 hours of sleep/night) vs HS for 6 weeks. Plasma testosterone levels were measured at baseline and end point (study 1) or baseline, week 3, and week 6 (study 2) of each phase. Linear model analyses to assess the effects of SR on testosterone were performed separately for each study.

RESULTS

Study 1: There were no significant sleep-time interaction on testosterone concentrations (change in testosterone levels during HS = 22.86 ± 163.79 ng/dL; SR = 43.73 ± 159.96 ng/dL, P = .41) and no main effect of sleep duration (P = .13). Study 2: There were a trend for a sleep-time interaction (P = .067) and a main effect of sleep on testosterone concentrations from 6 weeks of SR (P = .0046). Testosterone concentrations were slightly lower but increased over time with SR relative to HS.

CONCLUSIONS

Sleep restriction does not adversely affect plasma testosterone levels in healthy young men. Given prior contradicting evidence, confirmatory studies should be done to ascertain the influence of sleep duration and quality on testosterone concentrations in men throughout life.

Psychometric properties of a Japanese version of Composite Scale of Morningness

This study aimed to assess the factor structure and validity of the Composite Scale of Morningness (CSM) in Japanese samples. A sample of 348 Japanese university students (196 men, 152 women) and 170 adults from the community (50 men, 120 women) completed a questionnaire including the CSM, the Diurnal Type Scale (DTS) and questions regarding sleeping and waking times. Four measurement models were compared, and a two-factor measurement model with Morningness/Time of day preference (α = 0.78) and Morning Affect/Alertness (α = 0.80) factors yielded the closest fit. Both Morningness/Time of day preference and Morning Affect/Alertness were positively correlated with DTS score. Morningness/Ttime of day preference was negatively correlated with the midpoint of sleep on weekdays and free days. The measurement model was invariant across the university and community groups. The community group, which was older, was characterized by greater morningness. The results provide evidence of the validity of the Japanese CSM, thus opening up the possibility of including Japanese samples in cross-cultural research on morningness.

Owls, larks, swifts, woodcocks and they are not alone: A historical review of methodology for multidimensional self-assessment of individual differences in sleep-wake pattern

Differences between the so-called larks and owls representing the opposite poles of morningness-eveningness dimension are widely known. However, scientific consensus has not yet been reached on the methodology for ranking and typing people along other dimensions of individual variation in their sleep-wake pattern. This review focused on the history and state-of-the-art of the methodology for self-assessment of individual differences in more than one trait or adaptability of the human sleep-wake cycle. The differences between this and other methodologies for the self-assessment of trait- and state-like variation in the perceived characteristics of daily rhythms were discussed and the critical issues that remained to be addressed in future studies were highlighted. These issues include a) a failure to develop a unidimensional scale for scoring chronotypological differences, b) the inconclusive results of the long-lasting search for objective markers of chronotype, c) a disagreement on both number and content of scales required for multidimensional self-assessment of chronobiological differences, d) a lack of evidence for the reliability and/or external validity of most of the proposed scales and e) an insufficient development of conceptualizations, models and model-based quantitative simulations linking the differences between people in their sleep-wake pattern with the differences in the basic parameters of underlying chronoregulatory processes. It seems that, in the nearest future, the wide implementation of portable actigraphic and somnographic devices might lead to the development of objective methodologies for multidimensional assessment and classification of sleep-wake traits and adaptabilities.

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).

Marijuana use patterns and sleep among community-based young adults

Marijuana is the most commonly used recreational drug in the United States. Research on the relationship between marijuana and sleep is still in its infancy. The study examined differences in sleep characteristics between a community sample of daily users, non-daily marijuana users, and non-users. A total of 98 subjects (45 M; 53 F) participated. The mean age was 22.3 (standard deviation = 3.0). There were 53 females and 55% of the sample was Caucasian. Recruitment was done online and via print advertisements in the community. Groups were categorized as non-daily users (n = 29), daily users (n = 49), and non-user controls (n = 20). Sleep was characterized by the Pittsburgh Sleep Quality Index, Insomnia Severity Index, Epworth Sleepiness Scale, and the Morningness Eveningness Questionnaire. A standard cut off score of >10 for the Insomnia Severity Index was found in 38.8% of daily users, 10.3% of non-daily users, and 20% of non-users. Pittsburgh Sleep Quality Index scores in daily users (7.0+/-3.8) were higher than non-daily (4.9+/-3.2) and non-user controls (5.0+/-3.7), p = .02. Insomnia Severity Index scores in daily users (7.9+/-6.1) were higher than non-daily (5.1+/-4.3) and non-user controls (4.3+/-4.8), p = .01. Covariate adjusted regression analyses revealed mean Pittsburgh Sleep Quality Index and Insomnia Severity Index scores were significantly lower for non-daily users and controls relative to the daily users. When adjusting for depression and anxiety, these unique associations were not significant. There were no differences in the Epworth Sleepiness Scale or Morningness Eveningness Questionnaire. Daily marijuana users endorsed more sleep disturbance than non-daily users. Future studies should consider mood in the relationship between marijuana use and sleep.

Reviewing the psychometric properties of contemporary circadian typology measures

The accurate measurement of circadian typology (CT) is critical because the construct has implications for a number of health disorders. In this review, we focus on the evidence to support the reliability and validity of the more commonly used CT scales: the Morningness-Eveningness Questionnaire (MEQ), reduced Morningness-Eveningness Questionnaire (rMEQ), the Composite Scale of Morningness (CSM), and the Preferences Scale (PS). In addition, we also consider the Munich ChronoType Questionnaire (MCTQ). In terms of reliability, the MEQ, CSM, and PS consistently report high levels of reliability (>0.80), whereas the reliability of the rMEQ is satisfactory. The stability of these scales is sound at follow-up periods up to 13 mos. The MCTQ is not a scale; therefore, its reliability cannot be assessed. Although it is possible to determine the stability of the MCTQ, these data are yet to be reported. Validity must be given equal weight in assessing the measurement properties of CT instruments. Most commonly reported is convergent and construct validity. The MEQ, rMEQ, and CSM are highly correlated and this is to be expected, given that these scales share common items. The level of agreement between the MCTQ and the MEQ is satisfactory, but the correlation between these two constructs decreases in line with the number of "corrections" applied to the MCTQ. The interesting question is whether CT is best represented by a psychological preference for behavior or by using a biomarker such as sleep midpoint. Good-quality subjective and objective data suggest adequate construct validity for each of the CT instruments, but a major limitation of this literature is studies that assess the predictive validity of these instruments. We make a number of recommendations with the aim of advancing science. Future studies need to (1) focus on collecting data from representative samples that consider a number of environmental factors; (2) employ longitudinal designs to allow the predictive validity of CT measures to be assessed and preferably make use of objective data; (3) employ contemporary statistical approaches, including structural equation modeling and item-response models; and (4) provide better information concerning sample selection and a rationale for choosing cutoff points.

Circadian typology: a comprehensive review

The interest in the systematic study of the circadian typology (CT) is relatively recent and has developed rapidly in the two last decades. All the existing data suggest that this individual difference affects our biological and psychological functioning, not only in health, but also in disease. In the present study, we review the current literature concerning the psychometric properties and validity of CT measures as well as individual, environmental and genetic factors that influence the CT. We present a brief overview of the biological markers that are used to define differences between CT groups (sleep-wake cycle, body temperature, cortisol and melatonin), and we assess the implications for CT and adjustment to shiftwork and jet lag. We also review the differences between CT in terms of cognitive abilities, personality traits and the incidence of psychiatric disorders. When necessary, we have emphasized the methodological limitations that exist today and suggested some future avenues of work in order to overcome these. This is a new field of interest to professionals in many different areas (research, labor, academic and clinical), and this review provides a state of the art discussion to allow professionals to integrate chronobiological aspects of human behavior into their daily practice.

Self-determination: a buffer against suicide ideation

Self-determination was examined as a protective factor against the detrimental impact of negative life events on suicide ideation in adolescents. It is postulated that for highly self-determined adolescents, negative life events have a weaker impact on both hopelessness and suicide ideation than for non-self-determined adolescents. In turn, hopelessness is hypothesized to generate less suicide ideation for highly self-determined individuals. Results from multigroup analyses confirm that both the direct and indirect links between negative life events and suicide ideation were significantly weaker among participants high in self-determination. The protective role of self-determination against negative life events is discussed.

The Circadian Energy Scale (CIRENS): two simple questions for a reliable chronotype measurement based on energy

This study presents the Circadian Energy Scale (CIRENS), a very short and simple chronotype measurement tool based on energy. The CIRENS consists of two introspective questions about the usual energy level (very low, low, moderate, high, or very high, scored 1 to 5) in the morning and in the evening. The difference between energy level scores (-4 to 4) felt by respondents in the evening and morning defines the chronotype score and classification. A concurrent validity analysis of the CIRENS with the widely used Horne and Östberg Morningness-Eveningness Questionnaire (MEQ) was conducted using a sample of 225 college students, and with MSFsc, a sleep-based chronotype assessment tool based on the Munich Chronotype Questionnaire (MCTQ), using a sample of 34,530 subjects (18-83 yrs, 27% males). This large sample was collected in a Web survey for behavioral correlates of the CIRENS with variables previously associated with chronotype differences. The correlation of the CIRENS chronotype score was r = -.70 with the MEQ and r = .32 with the MSFsc. CIRENS chronotype scores declined with age and were not affected by sex. Both CIRENS and MSFsc chronotype scores were related to differences in tobacco, caffeine, and cola soft-drink consumption (all higher in evening types). The CIRENS provides a simple chronotype index and a measure of absolute energy throughout the day and seems to be a reliable chronotype assessment tool that may be useful both clinically and for large-scale studies.

Demographic factors, fatigue, and driving accidents: An examination of the published literature

This article reviews the literature pertaining to the association between demographic variables (e.g., age, sex, race, socio-economic status) with fatigue, and when feasible, accident risk. It also explores their potential influence and interaction with some working arrangements, commute time, personality characteristics, and circadian chronotype. Fatigue has been implicated in a range of impairments that can have detrimental effects on individuals, and it is differentially associated with conventional demographic variables. However, several major methodological limitations prevent clear conclusions. First, there is absence of a shared definition both within and across disciplines. Second, although fatigue has been investigated using a variety of diverse designs, they have either been too weak to substantiate causality or lacked ecological validity. Third, while both subjective and objective measures have been used as dependent variables, fatigue has been more often found to be more strongly linked with the former. Fourth, with the exception of age and sex, the influence of other demographic variables is unknown, since they have not yet been concomitantly assessed. In instances when they have been assessed and included in statistical analyses, they are considered as covariates or confounders; thus, their contribution to the outcome variable is controlled for, rather than being a planned aspect of investigation. Because the interaction of demographic factors with fatigue is largely a neglected area of study, we recommend greater interdisciplinary collaborations, incorporation of multiple demographic variables as independent factors, and use of within-participant analyses. These recommendations would provide meaningful results that may be used to inform public policy and preventive strategies.

Sleep disorders, medical conditions, and road accident risk

Sleep disorders and various common acute and chronic medical conditions directly or indirectly affect the quality and quantity of one's sleep or otherwise cause excessive daytime fatigue. This article reviews the potential contribution of several prevalent medical conditions - allergic rhinitis, asthma, chronic obstructive pulmonary disease, rheumatoid arthritis/osteoarthritis - and chronic fatigue syndrome and clinical sleep disorders - insomnia, obstructive sleep apnea, narcolepsy, periodic limb movement of sleep, and restless legs syndrome - to the risk for drowsy-driving road crashes. It also explores the literature on the cost-benefit of preventive interventions, using obstructive sleep apnea as an example. Although numerous investigations have addressed the impact of sleep and medical disorders on quality of life, few have specifically addressed their potential deleterious effect on driving performance and road incidents. Moreover, since past studies have focused on the survivors of driver crashes, they may be biased. Representative population-based prospective multidisciplinary studies are urgently required to clarify the role of the fatigue associated with common ailments and medications on traffic crash risk of both commercial and non-commercial drivers and to comprehensively assess the cost-effectiveness of intervention strategies.