Defeat and Entrapment Mediate the Relationship Between Insomnia Symptoms and Suicidal Ideation in Young Adults.

AIM: In recent years, there has been a growing interest in understanding the relationship between sleep disturbance and suicide. The current study aimed to advance understanding of the psychological processes driving these relationships by examining whether insomnia symptoms are related to suicidal ideation via perceptions of defeat and entrapment. METHODS: Young adults (n = 259; 202 students [78.0%], 45 employed [17.4%], 12 unemployed [4.6%]) completed an anonymous self-report survey that was advertised via social media, university participant pools, and fliers. The survey was described as being related to sleep and mood/mental health. Validated measures were used to assess insomnia symptoms, chronotype, defeat, entrapment, suicidal ideation, and affective covariates. RESULTS: Bivariate associations found insomnia severity to be related to poorer affective outcomes including severity of suicidal ideation. Insomnia and depression were significant independent variables in multiple linear regression with suidical ideation as the dependent variable. The relationship between insomnia and suicidal ideation was mediated by perceptions of defeat and entrapment. CONCLUSION: Taken together, these findings shed light on the psychological mechanisms linking sleep disturbance and suicidal ideation by highlighting the role of defeat and entrapment. These findings have the potential to improve suicide risk assessment and prevention in young adults experiencing difficulties initiating or maintaining sleep.HighlightsDefeat and entrapment mediate relationship between insomnia and suicidal ideationEvidence for Integrated Motivational-Volitional Model of Suicidal Behavior in community sampleUses validated multi-item suicide measure.

Insomnia symptoms mediate the association between eveningness and suicidal ideation, defeat, entrapment, and psychological distress in students.

Chronotype describes a person's general preference for mornings, evenings, or neither. It is typically conceptualized as a continuous unidimensional spectrum from morningness to eveningness. Eveningness is associated with poorer outcomes across a myriad of physical and mental health outcomes. This preference for later sleep and wake times is associated with increased risk of depression, anxiety, and suicidal ideation in both clinical and community samples. However, the mechanisms underlying the negative consequences of this preference for evenings are not fully understood. Previous research has found that sleep disturbances may act as a mediator of this relationship. The present study aimed to explore the associations between chronotype and affective outcomes in a sample of students. Additionally, it aimed to investigate the potential role of insomnia as a mediator within these relationships. Participants (n = 190) completed an anonymous self-report survey of validated measures online which assessed chronotype, insomnia symptoms, and a range of affective outcomes (defeat, entrapment, suicide risk, stress, and depressive and anxious symptomology). Eveningness was associated with more severe or frequent experiences of these outcomes, with participants that demonstrated a preference for eveningness more likely to report poorer affective functioning and increased psychological distress. Mediation analysis found the relationship between chronotype and these outcome measures was completely or partially mediated by insomnia symptom severity measured by the validated Sleep Condition Indicator insomnia scale. Taken together, these findings add further evidence for the negative consequences of increased eveningness. Additionally, our results show that chronotype and sleep disturbances should be considered when assessing mental well-being. Implementing appropriate sleep-related behavior change or schedule alterations can offer a tool for mitigation or prevention of psychological distress in students that report a preference for later sleep and wake times.

Nodding off but can't disconnect: development and validation of the iNOD index of Nighttime Offline Distress.

BACKGROUND: There is a pressing need to update sleep models, education and treatment to better reflect the realities of sleep in a 24/7 connected social world. Progress has been limited to date by available measurement tools, which have largely focused on the frequency or duration of individuals' social media use, without capturing crucial sleep-relevant aspects of this inherently social and interactive experience. METHODS: Survey data from 3008 adolescents (aged 10-18 years) was used to rigorously develop and validate a new self-report measure that quantifies difficulty disengaging from social media interactions at night: the index of Nighttime Offline Distress (iNOD). Exploratory and Confirmatory Factor analyses in a random split sample produced a ten-item two-factor solution, with subscales capturing concerns about Staying Connected and Following Etiquette (Cronbach's alphas = 0.91 and 0.92 respectively). RESULTS: Those with higher scores on these subscales tended to report using social media for longer after they felt they should be asleep (rs = 0.41 and 0.26, respectively), shorter sleep duration (rs = -0.24 and -0.17, respectively) and poorer sleep quality (rs = -0.33 and -0.31, respectively). Results also pointed towards a potentially fragmented process of sleep displacement for those who may struggle to disconnect - and to stay disconnected - from social interactions in order to allow sufficient uninterrupted sleep opportunity. CONCLUSIONS: These findings can inform current models for understanding normal and disordered sleep during adolescence, whilst highlighting specific social concerns as important potential targets for sleep education efforts.

Social media use and adolescent sleep patterns: cross-sectional findings from the UK millennium cohort study.

OBJECTIVES: This study examines associations between social media use and multiple sleep parameters in a large representative adolescent sample, controlling for a wide range of covariates. DESIGN: The authors used cross-sectional data from the Millennium Cohort Study, a large nationally representative UK birth cohort study. PARTICIPANTS: Data from 11 872 adolescents (aged 13-15 years) were used in analyses. METHODS: Six self-reported sleep parameters captured sleep timing and quality: sleep onset and wake times (on school days and free days), sleep onset latency (time taken to fall asleep) and trouble falling back asleep after nighttime awakening. Binomial logistic regressions investigated associations between daily social media use and each sleep parameter, controlling for a range of relevant covariates. RESULTS: Average social media use was 1 to <3 hours per day (31.6%, n=3720). 33.7% were classed as low users (<1 hour; n=3986); 13.9% were high users (3 to <5 hours; n=1602) and 20.8% were very high users (5+ hours; n=2203). Girls reported spending more time on social media than boys. Overall, heavier social media use was associated with poorer sleep patterns, controlling for covariates. For example, very high social media users were more likely than comparable average users to report late sleep onset (OR 2.14, 95% CI 1.83 to 2.50) and wake times (OR 1.97, 95% CI 1.32 to 2.93) on school days and trouble falling back asleep after nighttime awakening (OR 1.36, 95% CI 1.10 to 1.66). CONCLUSIONS: This study provides a normative profile of UK adolescent social media use and sleep. Results indicate statistically and practically significant associations between social media use and sleep patterns, particularly late sleep onset. Sleep education and interventions can focus on supporting young people to balance online interactions with an appropriate sleep schedule that allows sufficient sleep on school nights.

Identifying drivers for bedtime social media use despite sleep costs: The adolescent perspective.

OBJECTIVES: Bedtime social media use is associated with poor sleep during adolescence, which in turn contributes to poor mental health, impaired daytime functioning and lower academic achievement. However, the underlying drivers for these bedtime social media habits remain understudied. This study adds an adolescent perspective on motivations for bedtime social media use and perceived impact on sleep. METHODS: Adolescents aged 11-17 years (n = 24) participated in focus group discussions exploring their experiences of using social media, particularly at night. Inductive reflexive thematic analysis produced themes that captured underlying drivers for social media use and associated impact on sleep. RESULTS: Our analyses produced two overarching themes: Missing Out and Norms & Expectations. Adolescents' nighttime social media use was driven by concerns over negative consequences for real-world relationships if they disconnected (often reporting delayed bedtimes, insufficient sleep and daytime tiredness). These concerns included the risk of offline peer exclusion from missing out on online interactions, and the fear of social disapproval from violating norms around online availability and prompt responses. CONCLUSIONS: These findings offer novel insight into why adolescents may choose to prioritize social media over sleep. Researchers and practitioners can respond to the evolving needs of today's adolescents by approaching social media use not as a technology-based activity, but as an embedded social experience underpinned by the same concerns as offline interactions.

Genome-Wide Association Study of Circadian Rhythmicity in 71,500 UK Biobank Participants and Polygenic Association with Mood Instability.

BACKGROUND: Circadian rhythms are fundamental to health and are particularly important for mental wellbeing. Disrupted rhythms of rest and activity are recognised as risk factors for major depressive disorder and bipolar disorder. METHODS: We conducted a genome-wide association study (GWAS) of low relative amplitude (RA), an objective measure of rest-activity cycles derived from the accelerometer data of 71,500 UK Biobank participants. Polygenic risk scores (PRS) for low RA were used to investigate potential associations with psychiatric phenotypes. OUTCOMES: Two independent genetic loci were associated with low RA, within genomic regions for Neurofascin (NFASC) and Solute Carrier Family 25 Member 17 (SLC25A17). A secondary GWAS of RA as a continuous measure identified a locus within Meis Homeobox 1 (MEIS1). There were no significant genetic correlations between low RA and any of the psychiatric phenotypes assessed. However, PRS for low RA was significantly associated with mood instability across multiple PRS thresholds (at PRS threshold 0·05: OR = 1·02, 95% CI = 1·01-1·02, p = 9·6 × 10-5), and with major depressive disorder (at PRS threshold 0·1: OR = 1·03, 95% CI = 1·01-1·05, p = 0·025) and neuroticism (at PRS threshold 0·5: Beta = 0·02, 95% CI = 0·007-0·04, p = 0·021). INTERPRETATION: Overall, our findings contribute new knowledge on the complex genetic architecture of circadian rhythmicity and suggest a putative biological link between disrupted circadian function and mood disorder phenotypes, particularly mood instability, but also major depressive disorder and neuroticism. FUNDING: Medical Research Council (MR/K501335/1).

Association of disrupted circadian rhythmicity with mood disorders, subjective wellbeing, and cognitive function: a cross-sectional study of 91 105 participants from the UK Biobank.

BACKGROUND: Disruption of sleep and circadian rhythmicity is a core feature of mood disorders and might be associated with increased susceptibility to such disorders. Previous studies in this area have used subjective reports of activity and sleep patterns, but the availability of accelerometer-based data from UK Biobank participants permits the derivation and analysis of new, objectively ascertained circadian rhythmicity parameters. We examined associations between objectively assessed circadian rhythmicity and mental health and wellbeing phenotypes, including lifetime history of mood disorder. METHODS: UK residents aged 37-73 years were recruited into the UK Biobank general population cohort from 2006 to 2010. We used data from a subset of participants whose activity levels were recorded by wearing a wrist-worn accelerometer for 7 days. From these data, we derived a circadian relative amplitude variable, which is a measure of the extent to which circadian rhythmicity of rest-activity cycles is disrupted. In the same sample, we examined cross-sectional associations between low relative amplitude and mood disorder, wellbeing, and cognitive variables using a series of regression models. Our final model adjusted for age and season at the time that accelerometry started, sex, ethnic origin, Townsend deprivation score, smoking status, alcohol intake, educational attainment, overall mean acceleration recorded by accelerometry, body-mass index, and a binary measure of childhood trauma. FINDINGS: We included 91 105 participants with accelerometery data collected between 2013 and 2015 in our analyses. A one-quintile reduction in relative amplitude was associated with increased risk of lifetime major depressive disorder (odds ratio [OR] 1·06, 95% CI 1·04-1·08) and lifetime bipolar disorder (1·11, 1·03-1·20), as well as with greater mood instability (1·02, 1·01-1·04), higher neuroticism scores (incident rate ratio 1·01, 1·01-1·02), more subjective loneliness (OR 1·09, 1·07-1·11), lower happiness (0·91, 0·90-0·93), lower health satisfaction (0·90, 0·89-0·91), and slower reaction times (linear regression coefficient 1·75, 1·05-2·45). These associations were independent of demographic, lifestyle, education, and overall activity confounders. INTERPRETATION: Circadian disruption is reliably associated with various adverse mental health and wellbeing outcomes, including major depressive disorder and bipolar disorder. Lower relative amplitude might be linked to increased susceptibility to mood disorders. FUNDING: Lister Institute of Preventive Medicine.

Population-level seasonality in cardiovascular mortality, blood pressure, BMI and inflammatory cells in UK biobank.

INTRODUCTION: The risk of mortality from cardiovascular disease (CVD) is higher in wintertime throughout the world, but it is not known if this reflects annual changes in diet or lifestyle, or an endogenous photoperiodic mechanism that is sensitive to changes in day length. METHODS: Phenotypic data on cardiometabolic and lifestyle factors were collected throughout a 4 year time period from 502,642 middle-aged participants in UK Biobank. To assess the impact of seasonal environmental changes on cardiovascular risk factors, we linked these data to the outdoor temperature and day length at the time of assessment. Self-reported information on physical activity, diet and disease status were used to adjust for confounding factors related to health and lifestyle. RESULTS: Mortality related to CVD was higher in winter, as were risk factors for this condition including blood pressure, markers of inflammation and body mass index (BMI). These seasonal rhythms were significantly related to day length after adjustment for other factors that might affect seasonality including physical activity, diet and outdoor temperature. CONCLUSIONS: The risk of CVD may be modulated by day length at temperate latitudes, and the implications of seasonality should be considered in all studies of human cardiometabolic health. Key messages In this cross-sectional study in UK Biobank, we report annual variations in cardiovascular risk factors and mortality that were associated with day length independent of environmental and lifestyle factors. These seasonal changes in day length might contribute to annual patterns in cardiovascular disease and mortality.

Alterations in glutamatergic signaling contribute to the decline of circadian photoentrainment in aged mice.

Robust physiological circadian rhythms form an integral part of well-being. The aging process has been found to negatively impact systems that drive circadian physiology, typically manifesting as symptoms associated with abnormal/disrupted sleeping patterns. Here, we investigated the age-related decline in light-driven circadian entrainment in male C57BL/6J mice. We compared light-driven resetting of circadian behavioral activity in young (1-2 months) and old (14-18 months) mice and explored alterations in the glutamatergic pathway at the level of the circadian pacemaker, the suprachiasmatic nucleus (SCN). Aged animals showed a significant reduction in sensitivity to behavioral phase resetting by light. We show that this change was through alterations in N-Methyl-D-aspartate (NMDA) signaling at the SCN, where NMDA, a glutamatergic agonist, was less potent in inducing clock resetting. Finally, we show that this shift in NMDA sensitivity was through the reduced SCN expression of this receptor's NR2B subunit. Only in young animals did an NR2B antagonist attenuate behavioral resetting. These results can help target treatments that aim to improve both physiological and behavioral circadian entrainment in aged populations.

Sleep quality and paranoia: The role of alexithymia, negative emotions and perceptual anomalies.

Recent evidence suggests that sleep problems are associated with psychotic like experiences including paranoia. However, the mechanisms underpinning this association are not well understood and thus studies modelling hypothesised mediating factors are required. Alexithymia, the inability to recognise and describe emotions within the self may be an important candidate. In two separate studies we sought to investigate factors mediating the relationship between sleep quality and paranoia using a cross-sectional design. Healthy volunteers without a mental health diagnosis were recruited (study 1, N = 401, study 2, N = 402). Participants completed a series of measures assessing paranoia, negative emotions, alexithymia and perceptual anomalies in an online survey. In study 1, regression and mediation analyses showed that the relationship between sleep quality and paranoia was partially mediated by alexithymia, perceptual anomalies and negative affect. In contrast, study 2 found that the relationship between sleep quality and paranoia was fully mediated by negative affect, alexithymia and perceptual anomalies. The link between sleep quality and paranoia is unclear and reasons for discrepant results are discussed. Novel findings in this study include the link between alexithymia and paranoia.

Clinician perceptions of sleep problems, and their treatment, in patients with non-affective psychosis.

Aims and method: To assess clinicians' views about their understanding and treatment of sleep problems in people with non-affective psychosis. An online survey was emailed to adult mental health teams in two NHS trusts. Results: One hundred and eleven clinicians completed the survey. All clinicians reported disrupted sleep in their patients, and endorsed the view that sleep and psychotic experiences each exacerbate the other. However, most clinicians (n = 92, 82%) assessed sleep problems informally, rather than using standard assessment measures. There was infrequent use of the recommended cognitive-behavioural treatments for sleep problems such as persistent insomnia, with the approaches typically used being sleep hygiene and medications instead. Clinical implications: Clinicians recognise the importance of sleep in psychosis, but the use of formal assessments and recommended treatments is limited. Barriers to treatment implementation identified by the clinicians related to services (e.g. lack of time), patients (e.g. their lifestyle) and environmental features of inpatient settings.

Attention to beds in natural scenes by observers with insomnia symptoms.

Attention biases to sleep-related stimuli are held to play a key role in the development and maintenance of insomnia, but such biases have only been shown with controlled visual displays. This study investigated whether observers with insomnia symptoms allocate attention to sleep-related items in natural scenes, by recording eye movements during free-viewing of bedrooms. Participants with insomnia symptoms and normal sleepers were matched in their visual exploration of these scenes, and there was no evidence that the attention of those with insomnia symptoms was captured more quickly by sleep-related stimuli than that of normal sleepers. However, the insomnia group fixated bed regions on more trials and, once fixated on a bed, also remained there for longer. These findings indicate that sleep stimuli are particularly effective in retaining visual attention in complex natural scenes.

Sleep characteristics modify the association of genetic predisposition with obesity and anthropometric measurements in 119,679 UK Biobank participants.

Background: Obesity is a multifactorial condition influenced by genetics, lifestyle, and environment.Objective: We investigated whether the association of a validated genetic profile risk score for obesity (GPRS-obesity) with body mass index (BMI) and waist circumference (WC) was modified by sleep characteristics.Design: This study included cross-sectional data from 119,859 white European adults, aged 37-73 y, participating in the UK Biobank. Interactions of GPRS-obesity and sleep characteristics (sleep duration, chronotype, day napping, and shift work) with their effects on BMI and WC were investigated. Results: ß Values are expressed as the change in BMI (in kg/m2) or WC per 1-SD increase in GPRS-obesity. The GPRS-obesity was associated with BMI (ß: 0.57; 95% CI: 0.55, 0.60; P = 6.3 × 10-207) and WC (1.21 cm; 95% CI: 1.15, 1.28 cm; P = 4.2 × 10-289). There were significant interactions of GPRS-obesity and a variety of sleep characteristics with their relation with BMI (P-interaction < 0.05). In participants who slept <7 or >9 h daily, the effect of GPRS-obesity on BMI was stronger (ß: 0.60; 95% CI: 0.54, 0.65 and ß: 0.73; 95% CI: 0.49, 0.97, respectively) than in normal-length sleepers (7-9 h; ß: 0.52; 95% CI: 0.49, 0.55). A similar pattern was observed for shift workers (ß: 0.68; 95% CI: 0.59, 0.77 compared with ß: 0.54; 95% CI: 0.51, 0.58 for non-shift workers) and for night-shift workers (ß: 0.69; 95% CI: 0.56, 0.82 compared with ß: 0.55; 95% CI: 0.51, 0.58 for non-night-shift workers), for those taking naps during the day (ß: 0.65; 95% CI: 0.52, 0.78 compared with ß: 0.51; 95% CI: 0.48, 0.55 for those who never or rarely had naps), and for those with a self-reported evening chronotype (ß: 0.72; 95% CI: 0.61, 0.82 compared with ß: 0.52; 95% CI: 0.47, 0.57 for morning chronotype). Similar findings were obtained by using WC as the outcome.Conclusion: This study shows that the association between genetic risk for obesity and phenotypic adiposity measures is exacerbated by adverse sleeping characteristics.

Adverse metabolic and mental health outcomes associated with shiftwork in a population-based study of 277,168 workers in UK biobank.

BACKGROUND: Reported associations between shiftwork and health have largely been based on occupation-specific, or single sex studies that might not be generalizable to the entire working population. The objective of this study was to investigate whether shiftwork was independently associated with obesity, diabetes, poor sleep, and well-being in a large, UK general population cohort. METHODS: Participants of the UK Biobank study who were employed at the time of assessment were included. Exposure variables were self-reported shiftwork (any shiftwork and night shiftwork); and outcomes were objectively measured obesity, inflammation and physical activity and self-reported lifestyle, sleep and well-being variables, including mental health. RESULTS: Shiftwork was reported by 17% of the 277,168 employed participants. Shiftworkers were more likely to be male, socioeconomically deprived and smokers, and to have higher levels of physical activity. Univariately, and following adjustment for lifestyle and work-related confounders, shiftworkers were more likely to be obese, depressed, to report disturbed sleep, and to have neurotic traits. CONCLUSIONS: Shiftwork was independently associated with multiple indicators of poor health and wellbeing, despite higher physical activity, and even in shiftworkers that did not work nights. Shiftwork is an emerging social factor that contributes to disease in the urban environment across the working population. Key messages Studies have linked shiftwork to obesity and diabetes in nurses and industry workers, but little is known about the implications of shiftwork for the general workforce In this large cross sectional study of UK workers, shiftwork was associated with obesity, depression and sleep disturbance, despite higher levels of physical activity. Shiftwork was associated with multiple indicators of compromised health and wellbeing and were more likely to report neurotic traits and evening preference.

Chronic photoperiod disruption does not increase vulnerability to focal cerebral ischemia in young normotensive rats.

Photoperiod disruption, which occurs during shift work, is associated with changes in metabolism or physiology (e.g. hypertension and hyperglycaemia) that have the potential to adversely affect stroke outcome. We sought to investigate if photoperiod disruption affects vulnerability to stroke by determining the impact of photoperiod disruption on infarct size following permanent middle cerebral artery occlusion. Adult male Wistar rats (210-290 g) were housed singly under two different light/dark cycle conditions ( n = 12 each). Controls were maintained on a standard 12:12 light/dark cycle for nine weeks. For rats exposed to photoperiod disruption, every three days for nine weeks, the lights were switched on 6 h earlier than in the previous photoperiod. T2-weighted magnetic resonance imaging was performed at 48 h after middle cerebral artery occlusion. Disruption of photoperiod in young healthy rats for nine weeks did not alter key physiological variables that can impact on ischaemic damage, e.g. blood pressure and blood glucose immediately prior to middle cerebral artery occlusion. There was no effect of photoperiod disruption on infarct size after middle cerebral artery occlusion. We conclude that any potentially adverse effect of photoperiod disruption on stroke outcome may require additional factors such as high fat/high sugar diet or pre-existing co-morbidities.

Perceptual impairment in face identification with poor sleep.

Previous studies have shown impaired memory for faces following restricted sleep. However, it is not known whether lack of sleep impairs performance on face identification tasks that do not rely on recognition memory, despite these tasks being more prevalent in security and forensic professions-for example, in photo-ID checks at national borders. Here we tested whether poor sleep affects accuracy on a standard test of face-matching ability that does not place demands on memory: the Glasgow Face-Matching Task (GFMT). In Experiment 1, participants who reported sleep disturbance consistent with insomnia disorder show impaired accuracy on the GFMT when compared with participants reporting normal sleep behaviour. In Experiment 2, we then used a sleep diary method to compare GFMT accuracy in a control group to participants reporting poor sleep on three consecutive nights-and again found lower accuracy scores in the short sleep group. In both experiments, reduced face-matching accuracy in those with poorer sleep was not associated with lower confidence in their decisions, carrying implications for occupational settings where identification errors made with high confidence can have serious outcomes. These results suggest that sleep-related impairments in face memory reflect difficulties in perceptual encoding of identity, and point towards metacognitive impairment in face matching following poor sleep.

How are normal sleeping controls selected? A systematic review of cross-sectional insomnia studies and a standardized method to select healthy controls for sleep research.

There appears to be some inconsistency in how normal sleepers (controls) are selected and screened for participation in research studies for comparison with insomnia patients. The purpose of the current study is to assess and compare methods of identifying normal sleepers in insomnia studies, with reference to published standards. We systematically reviewed the literature on insomnia patients, which included control subjects. The resulting 37 articles were systematically reviewed with reference to the five criteria for normal sleep specified by Edinger et al. In summary, these criteria are as follows: evidence of sleep disruption, sleep scheduling, general health, substance/medication use, and other sleep disorders. We found sleep diaries, polysomnography (PSG), and clinical screening examinations to be widely used with both control subjects and insomnia participants. However, there are differences between research groups in the precise definitions applied to the components of normal sleep. We found that none of the reviewed studies applied all of the Edinger et al. criteria, and 16% met four criteria. In general, screening is applied most rigorously at the level of a clinical disorder, whether physical, psychiatric, or sleep. While the Edinger et al. criteria seem to be applied in some form by most researchers, there is scope to improve standards and definitions in this area. Ideally, different methods such as sleep diaries and questionnaires would be used concurrently with objective measures to ensure normal sleepers are identified, and descriptive information for control subjects would be reported. Here, we have devised working criteria and methods to be used for the assessment of normal sleepers. This would help clarify the nature of the control group, in contrast to insomnia subjects and other patient groups.

Social interactions, emotion and sleep: A systematic review and research agenda.

Sleep and emotion are closely linked, however the effects of sleep on socio-emotional task performance have only recently been investigated. Sleep loss and insomnia have been found to affect emotional reactivity and social functioning, although results, taken together, are somewhat contradictory. Here we review this advancing literature, aiming to 1) systematically review the relevant literature on sleep and socio-emotional functioning, with reference to the extant literature on emotion and social interactions, 2) summarize results and outline ways in which emotion, social interactions, and sleep may interact, and 3) suggest key limitations and future directions for this field. From the reviewed literature, sleep deprivation is associated with diminished emotional expressivity and impaired emotion recognition, and this has particular relevance for social interactions. Sleep deprivation also increases emotional reactivity; results which are most apparent with neuro-imaging studies investigating amygdala activity and its prefrontal regulation. Evidence of emotional dysregulation in insomnia and poor sleep has also been reported. In general, limitations of this literature include how performance measures are linked to self-reports, and how results are linked to socio-emotional functioning. We conclude by suggesting some possible future directions for this field.

The bright-nights and dim-days of the urban photoperiod: implications for circadian rhythmicity, metabolism and obesity.

Artificial light decreases the amplitude of daily rhythms in human lifestyle principally by permitting activity and food intake to occur during hours of darkness, and allowing day-time activity to occur in dim light, indoors. Endogenous circadian timing mechanisms that oscillate with a period of 24 h have evolved to ensure physiology is synchronized with the daily variations in light, food, and social cues of the environment. Artificial light affects the synchronization between these oscillators, and metabolic disruption may be one consequence of this. By dampening the amplitude of environmental timing cues and disrupting circadian rhythmicity, artificial lighting might initiate metabolic disruption and contribute to the association between global urbanization and obesity. The aim of this review is to explore the historical, physiological, and epidemiological relationships between artificial light and circadian and metabolic dysfunction.