The Mind After Midnight: Nocturnal Wakefulness, Behavioral Dysregulation, and Psychopathology

Empirical clustering to identify individuals for whom insomnia is more closely related to suicidal ideation

BACKGROUND

Although the effect sizes are modest, insomnia is consistently associated with suicidal thoughts and behaviors. Subgroup analyses can efficiently identify for whom insomnia is most relevant to suicidal ideation. To improve clinical case identification, the present study sought to identify subclusters of lifetime suicidal ideators for whom insomnia was most closely related to current suicidal ideation.

METHODS

Data on N = 4750 lifetime suicidal ideators were extracted from the Military Suicide Research Consortium's Common Data Elements. Data on sociodemographic characteristics, severity and history of suicidal thoughts and behaviors, and related clinical characteristics were clustered by unsupervised machine learning algorithms. Robust Poisson regression estimated cluster by insomnia associations with current suicidal ideation.

RESULTS

Three clusters were identified: a modest symptom severity cluster (N = 1757, 37.0 %), an elevated severity cluster (N = 1444 30.4 %), and a high severity cluster (N = 1549 32.6 %). In Cluster 1, insomnia was associated with current suicidal ideation (PRR 1.29 [1.13-1.46]) and remained significant after adjusting for sociodemographic and clinical covariates. In Cluster 2, insomnia was associated with current suicidal ideation (PRR 1.14 [1.01-1.30]), but not after adjusting for sociodemographic and clinical covariates. In Cluster 3, insomnia was associated with current suicidal ideation (PRR 1.12 [1.03-1.21]) and remained significant after adjusting for sociodemographic covariates, but not clinical covariates.

LIMITATIONS

Cross-sectional design, lack of diagnostic data, non-representative sample.

CONCLUSION

Insomnia appears more closely related to current suicidal ideation among modest severity individuals than other subgroups. Future work should use prospective designs and more comprehensive risk factor measures to confirm these findings.

Role of the Locus Coeruleus Arousal Promoting Neurons in Maintaining Brain Criticality across the Sleep-Wake Cycle

Sleep control depends on a delicate interplay among brain regions. This generates a complex temporal architecture with numerous sleep-stage transitions and intermittent fluctuations to micro-states and brief arousals. These temporal dynamics exhibit hallmarks of criticality, suggesting that tuning to criticality is essential for spontaneous sleep-stage and arousal transitions. However, how the brain maintains criticality remains not understood. Here, we investigate θ- and δ-burst dynamics during the sleep-wake cycle of rats (Sprague-Dawley, adult male) with lesion in the wake-promoting locus coeruleus (LC). We show that, in control rats, θ- and δ-bursts exhibit power-law (θ-bursts, active phase) and exponential-like (δ-bursts, quiescent phase) duration distributions, as well as power-law long-range temporal correlations (LRTCs)-typical of non-equilibrium systems self-organizing at criticality. Furthermore, consecutive θ- and δ-bursts durations are characterized by anti-correlated coupling, indicating a new class of self-organized criticality that emerges from underlying feedback between neuronal populations and brain areas involved in generating arousals and sleep states. In contrast, we uncover that LC lesion leads to alteration of θ- and δ-burst critical features, with change in duration distributions and correlation properties, and increase in θ-δ coupling. Notably, these LC-lesion effects are opposite to those observed for lesions in the sleep-promoting ventrolateral preoptic (VLPO) nucleus. Our findings indicate that critical dynamics of θ- and δ-bursts arise from a balanced interplay of LC and VLPO, which maintains brain tuning to criticality across the sleep-wake cycle-a non-equilibrium behavior in sleep micro-architecture at short timescales that coexists with large-scale sleep-wake homeostasis.

Identifying mechanistic links between sleep disturbance and binge eating: the role of depressed mood

Global sleep disturbance is robustly linked with a subjective sense of loss-of-control over eating (LOC). Depressed mood has been proposed as a mechanism to explain the bi-directional relationship between sleep disturbance and LOC eating. The current study evaluated whether sleep disturbance indirectly affects LOC eating via depressed mood. Adults seeking treatment for a DSM-5 binge-spectrum eating disorder (e.g. bulimia nervosa, binge-eating disorder) were recruited (n = 79) and asked to complete self-report questionnaires assessing sleep disturbance and depression, and a semi-structured interview assessing LOC eating. Tests of indirect effects evaluated the effect of depressed mood on the association between global sleep disturbance and LOC frequency covarying for BMI and parent study. A significant indirect effect of depressed mood on the association between global sleep disturbance and frequency of LOC eating was identified (Est = 1.519, S.E. = 0.859, p = .033). The indirect effect of depressed mood on the association between sleep disturbance and LOC eating may indicate that depressed mood serves as a mechanistic link between sleep disturbance and LOC eating. The findings offer preliminary support for adjunctive treatments targeting both sleep disturbance and depressed mood for LOC eating. Future research should explore these pathways in a larger clinical sample.

Diurnal variation in anxiety and activity is influenced by chronotype and probable anxiety-related disorder status

Anxiety symptoms vary moment-to-moment within a day. One factor that may influence these variations is chronotype. Evening chronotypes prefer to engage in activities (e.g., sleep, physical and social activity) later in the day, and evening chronotype is implicated in psychopathology, including anxiety-related disorders. However, it is unknown whether chronotype influences diurnal variation in anxiety symptoms and whether these effects are amplified in individuals with a probable anxiety-related disorder. We examined the diurnal variation in anxiety symptoms and daily activities in morning and evening chronotypes with and without probable generalized anxiety disorder (GAD) or obsessive-compulsive disorder (OCD) in a community sample of adults (N = 410). Evening chronotypes reported higher anxiety symptoms, particularly in the evening hours, and lower engagement in daily activities, predominantly in the morning hours. Evening chronotypes with probable GAD or OCD reported worse anxiety symptoms in the evening. Our findings indicate that anxiety symptoms and engagement in daily activities fluctuate considerably across the day, and these patterns differ depending on chronotype. Evening chronotypes have more anxiety symptoms in the evening, despite preferring this time of day. Personalized treatment approaches that consider chronotype and target certain times of day may be efficient in alleviating peaks in anxiety symptoms.

[Effects of Extreme Environments on Human Sleep]

Recently, with the rapid growth of the global population and the exhaustion of resources, exploration activities in extreme environments such as the polar regions, the outer space, the deep sea, the deep underground and highlands are becoming increasingly more frequent. This in-depth exploration of the external environment and the consequent dramatic changes in lifestyles impact on sleep, a basic life activity of humans, in ways that cannot be overlooked. the basic life activity of human beings. Sleep, a basic life activity and the result of the evolution of organisms to adapt to their environment, is closely associated with sleep homeostasis and endogenous rhythms. However, external environmental changes and lifestyle shifts in extreme environments have had a significant impact on the patterns and the quality of sleep in humans. Furthermore, this impact can lead to many physiological and psychological problems, posing a great threat to human health. In this review, we delved into the specific effects of different extreme natural environments and enclosed environments on sleep, elaborating on how these environments alter the patterns and the quality of sleep in humans. In addition, we summarized the changes in human sleep under extreme environments to help gain a better understanding of the mechanisms by which these specific environments impact human sleep. It is expected that this review will provide a solid theoretical foundation for optimizing long-term survival strategies in extreme environments and help humans adapt to and overcome the challenges posed by extreme environments more effectively.

Daily sleepiness magnifies the relation between same-day passive and active suicide ideation

Disrupted sleep has been linked to suicidal thoughts and behavior. Less is known, however, about the underlying mechanisms of this relationship. A more nuanced understanding of the link between sleep and suicide may help inform treatment decisions and the development of prevention and intervention strategies. The present study examined daily average sleepiness as a moderator to the relation between same-day passive and active suicide ideation (SI). Fifty-nine young adults (mean age = 21.04; SD = 2.22) endorsing SI at least twice in the two weeks prior to baseline completed 3-5 daily surveys of sleepiness and SI over 2 weeks as part of a broader study. Across several indicators of sleepiness (desire to stay awake, desire to fall asleep), passive SI (desire to die, desire to live), and active SI (occurrence, intensity, duration, and controllability), the overall findings demonstrated that daily average sleepiness magnified the relation between same-day passive SI and active SI severity. These findings indicate that being sleepier than usual may increase the likelihood that passive SI transitions to active SI. Future research is needed to test the causal influence of sleepiness on this transition.

Perils of the nighttime: Impact of behavioral timing and preference on mental health in 73,888 community-dwelling adults

Mental health is independently influenced by the inclination to sleep at specific times (chronotype) and the actual sleep timing (behavior). Chronotype and timing of actual sleep are, however, often misaligned. This study aims to determine how chronotype, sleep timing, and the alignment between the two impact mental health. In a community-dwelling cohort of middle- and older-aged adults (UK Biobank, n = 73,888), we examined the impact of chronotype (questionnaire-based), the timing of behavior (determined with 7-day accelerometry), and the alignment between the two on mental, behavioral, neurodevelopmental disorders (MBN), depression, and anxiety, as assessed through ICD-10 codes. As compared to morning types with early behavior (aligned), morning types with late behavior (misaligned) had an increased risk of having MBN, depression, and anxiety (p's<0.001). As compared to evening-types with late behavior (aligned), however, evening-types with early behavior (misaligned) had a decreased risk of depression (p < 0.01), with a trend for MBN (p = 0.04) and anxiety (p = 0.05). Longitudinal analyses, in which the likelihood of developing de novo mental health disorders was associated with chronotype, behavioral timing, and alignment between the two, confirmed cross-sectional findings. To age healthily, individuals should start sleeping before 1AM, despite chronobiological preferences.

Estimating Community Disruption from Nighttime Gunshots in 6 U.S. Cities, 2015 to 2021

BACKGROUND

Gunshots affect those directly involved in an incident and those in the surrounding community. The community-level impact of nighttime gunshots, which may be particularly disruptive to the sleep of nearby community members, is unknown.

OBJECTIVE

Our aim is to estimate the number of people potentially affected by nighttime gunshots and the relationship between nighttime gunshots and median household income in the USA.

DESIGN

We collected publicly available data on the timing and location of gunshots in six U.S. cities (Baltimore, MD; Boston, MA; Washington, D.C.; New York, NY; Philadelphia, PA; and Portland, OR) from 2015 to 2021. We then analyzed the data by computing rate ratios (RRs) to compare the frequency of gunshots during nighttime hours (6:00 pm to 5:59 am) versus daytime hours (6:00 am to 5:59 pm). Additionally, we used geospatial mapping to create choropleth maps to visualize the variation in nighttime gunshot density across cities. We estimated, using city-wide population, person-nights potentially impacted by the sound of gunshots within areas of 0.2- (low) and 0.5-mile (high) radius. Finally, for five of six cities where data on median household income were available by census tract, we built nonlinear regression models to estimate the relationship between the number of nighttime gunshots and median household income.

KEY RESULTS

We analyzed 72,236 gunshots. Gunshots were more common during the nighttime than daytime (overall RR = 2.5). Analyses demonstrated that the low estimates for the mean annual number of person-nights impacted by nighttime gunshots were 0.4 million in Baltimore and Portland, 1.3 million in Philadelphia, 1.6 million in Boston, 2.9 million in New York City, and 5.9 million in Washington. The number of nighttime gunshots was inversely related to median household income.

CONCLUSIONS

Nighttime gunshots are prevalent, particularly in low-income neighborhoods, and may have under-recognized effects on the surrounding community.

Social and circadian rhythm dysregulation and suicide: A systematic review and meta-analysis

This systematic review of 52 studies provides a quantitative synthesis of the empirical literature on social and circadian rhythm correlates of suicidal thoughts and behaviors (STB). Small-to-medium pooled effect sizes were observed for associations between evening chronotype and STB and suicidal ideation (SI), although the pooled effect size diminished when accounting for publication bias. Three studies employed longitudinal designs and suggested eveningness was predictive of future STB, with a small-to-medium effect size. Social rhythm irregularity was also a significant correlate of STB with pooled effect sizes in the medium range. Overall circadian rhythm disruption was not associated with STB, although certain circadian rhythm metrics, including mean daytime activity, circadian rhythm sleep-wake disorder diagnosis, and actigraphy-assessed amplitude were associated with STB. Pooled effect sizes for these indices were in the medium to large range. There is a need for additional longitudinal research on actigraphy-based circadian parameters and objective markers of circadian phase (i.e., dim-light melatonin onset) to gain a clearer understanding of associations of endogenous circadian function and STB beyond that which can be captured via self-report.

The sleep-circadian interface: A window into mental disorders

Sleep, circadian rhythms, and mental health are reciprocally interlinked. Disruption to the quality, continuity, and timing of sleep can precipitate or exacerbate psychiatric symptoms in susceptible individuals, while treatments that target sleep-circadian disturbances can alleviate psychopathology. Conversely, psychiatric symptoms can reciprocally exacerbate poor sleep and disrupt clock-controlled processes. Despite progress in elucidating underlying mechanisms, a cohesive approach that integrates the dynamic interactions between psychiatric disorder with both sleep and circadian processes is lacking. This review synthesizes recent evidence for sleep-circadian dysfunction as a transdiagnostic contributor to a range of psychiatric disorders, with an emphasis on biological mechanisms. We highlight observations from adolescent and young adults, who are at greatest risk of developing mental disorders, and for whom early detection and intervention promise the greatest benefit. In particular, we aim to a) integrate sleep and circadian factors implicated in the pathophysiology and treatment of mood, anxiety, and psychosis spectrum disorders, with a transdiagnostic perspective; b) highlight the need to reframe existing knowledge and adopt an integrated approach which recognizes the interaction between sleep and circadian factors; and c) identify important gaps and opportunities for further research.

Characterizing Gun Violence by Time, Day of the Week, Holidays, and Month in 6 US Cities, 2015-2021

Developing interventions to prevent firearm-related violence and to address its consequences requires an improved understanding of when these violent events are most likely to occur. We explored gunshot events in 6 of the most populated cities in the United States by time of day, day of week, holiday/non-holiday, and month using publicly available datasets. In some of these cities, gunshot events occurred most often at nighttime, on holidays and weekends, and during summer months, with significant interaction effects. There were also time-related changes in characteristics of the victims. Primary prevention efforts aimed at curbing firearm-related violence should consider these differential risks.

Animal models of human insomnia

Insomnia disorder (chronic sleep continuity disturbance) is a debilitating condition affecting 5%-10% of the adult population worldwide. To date, researchers have attempted to model insomnia in animals through breeding strategies that create pathologically short-sleeping individuals or with drugs and environmental contexts that directly impose sleeplessness. While these approaches have been invaluable for identifying insomnia susceptibility genes and mapping the neural networks that underpin sleep-wake regulation, they fail to capture concurrently several of the core clinical diagnostic features of insomnia disorder in humans, where sleep continuity disturbance is self-perpetuating, occurs despite adequate sleep opportunity, and is often not accompanied by significant changes in sleep duration or architecture. In the present review, we discuss these issues and then outline ways animal models can be used to develop approaches that are more ecologically valid in their recapitulation of chronic insomnia's natural aetiology and pathophysiology. Conditioning of self-generated sleep loss with these methods promises to create a better understanding of the neuroadaptations that maintain insomnia, including potentially within the infralimbic cortex, a substrate at the crossroads of threat habituation and sleep.

An Examination of the Associations between Nutritional Composition, Social Jet Lag and Temporal Sleep Variability in Young Adults

While dietary intake has previously been related to various indices of poor sleep (e.g., short sleep duration, poor sleep quality), to date, few studies have examined chrononutrition from the perspectives of the relationship between dietary intake and social jet lag and temporal sleep variability. Moreover, recently it has been suggested that previous methods of measuring social jet lag have the potential to lead to large overestimations. Together, this precludes a clear understanding of the role of nutritional composition in the pathophysiology of poor sleep, via social jet lag and temporal sleep variability, or vice versa. The aim of the present study was to determine the relationships between nutrient intake and social jet lag (using a revised index, taking account of intention to sleep and sleep onset and offset difficulties), and temporal sleep variability. Using a cross-sectional survey, 657 healthy participants (mean age 26.7 ± 6.1 years), without sleep disorders, were recruited via an online platform and completed measures of weekly dietary intake, social jet lag, temporal sleep variability, stress/sleep reactivity and mood. Results showed limited associations between nutritional composition and social jet lag. However, levels of temporal sleep variability were predicted by consumption of polyunsaturated fats, sodium, chloride and total energy intake. The results suggest further examinations of specific nutrients are warranted in a first step to tailoring interventions to manage diet and temporal variabilities in sleep patterns.

Examining sleep disturbance components as near-term predictors of suicide ideation in daily life

Suicide ideation emerges and fluctuates over short timeframes (minutes, hours, days); however, near-term predictors of such fluctuations have not been well-elucidated. Sleep disturbance is a distal suicide risk factor, but less work has examined whether daily sleep disturbance predicts near-term changes in suicide ideation. We examined subjective sleep disturbance components as predictors of passive and active suicide ideation at the within-person (i.e., day-to-day changes within individuals relative to their own mean) and between-persons (individual differences relative to the sample mean) levels. A transdiagnostic sample of 102 at-risk young adults ages 18-35 completed a 21-day ecological momentary assessment protocol, during which they reported on sleep and passive and active suicide ideation. At the within-persons level, nightmares, sleep quality, and wake after sleep onset predicted passive suicide ideation, and sleep quality and wake after sleep onset predicted active suicide ideation. At the between-persons level, nightmares, sleep onset latency, and sleep quality were associated with passive suicide ideation, and sleep onset latency was associated with active suicide ideation. In contrast, suicide ideation did not predict subsequent sleep at the within-person level. Specific sleep disturbance components are near-term predictors of intraindividual increases in suicide ideation and may hold promise for suicide prevention and intervention.

Fatigue and its impact on performance and health

An increasing body of evidence suggests that fatigue among healthcare staff is widespread, owing to a combination of high work intensity, long daytime hours and night-shift working. This has been linked to poorer outcomes for patients and longer inpatient stays, and to increased risks of work-related accidents, errors and injuries for practitioners. These include needlestick injuries and motor vehicle accidents, and other impacts on practitioner health, ranging from cancer, mental health problems, metabolic disorders to coronary disease. Other 24-hour safety-critical industries have fatigue policies that acknowledge the risks of staff fatigue and provide a system to manage it and mitigate harm, but these are still lacking within healthcare. This review explains the basic physiology behind fatigue and outlines its impacts on healthcare practitioners' clinical practice and wellbeing. It proposes methods to minimise these effects for individuals, organisations and the wider UK health service.

Insomnia and the Interpersonal Theory of suicide among civilians, service members, and veterans

BACKGROUND

Insomnia is associated with suicide risk in civilian and military populations. Thwarted belongingness is proposed as a mediator of this relationship under the Interpersonal Theory of Suicide (IPTS). The present study explored how insomnia relates to suicidal ideation in conjunction with thwarted belongingness among civilians, Service members, and Veterans.

METHODS

Data from the Military Suicide Research Consortium for N = 6556 individuals (6316 with non-missing suicidal ideation status) were divided into 4 subgroups: civilians, never deployed Service members, previously deployed Service members, and Veterans. Robust Poisson models evaluated the associations between insomnia severity/subtype and current suicidal ideation, with bootstrap mediation models assessing thwarted belongingness as a mediator.

RESULTS

A 5-point increase in insomnia severity was associated with a 38% increased risk for current suicidal ideation among civilians, a 56% greater risk among never deployed Service members, an 83% greater risk among previously deployed Service members, and a 37% greater risk among Veterans. Moreover, active Service members showed greater associations between difficulty falling asleep and staying asleep with suicidal ideation than civilians. These associations were independent of covariates and only mediated by thwarted belongingness among Veterans.

CONCLUSIONS

The relationship between insomnia and suicide is not purely explained by thwarted belongingness except among Veterans. Future research should explore additional psychological and neurobiological mechanisms connecting insomnia and suicidality.

The circadian system, sleep, and the health/disease balance: a conceptual review

The field of "circadian medicine" is a recent addition to chronobiology and sleep research efforts. It represents a logical step arising from the increasing insights into the circadian system and its interactions with life in urbanised societies; applying these insights to the health/disease balance at home and in the medical practice (outpatient) and clinic (inpatient). Despite its fast expansion and proliferating research efforts, circadian medicine lacks a formal framework to categorise the many observations describing interactions among the circadian system, sleep, and the health/disease balance. A good framework allows us to categorise observations and then assign them to one or more components with hypothesised interactions. Such assignments can lead to experiments that document causal (rather than correlational) relationships and move from describing observations to discovering mechanisms. This review details such a proposed formal framework for circadian medicine and will hopefully trigger discussion among our colleagues, so that the framework can be improved and expanded. As the basis of the framework for circadian medicine, we define "circadian health" and how it links to general health. We then define interactions among the circadian system, sleep, and the health/disease balance and put the framework into the context of the literature with examples from six domains of health/disease balance: fertility, cancer, immune system, mental health, cardiovascular, and metabolism.