Twin-based heritability of actimetry traits

Mouse Models in Circadian Rhythm and Melatonin Research

This contribution reviews the role of inbred and transgenic mouse strains for deciphering the mammalian melatoninergic and circadian system. It focusses on the pineal organ as melatonin factory and two major targets of the melatoninergic system, the suprachiasmatic nuclei (SCN) and the hypophysial pars tuberalis (PT). Mammalian pinealocytes sharing molecular characteristics with true pineal and retinal photoreceptors synthesize and secrete melatonin into the blood and cerebrospinal fluid night by night. Notably, neuron-like connections exist between the deep pinealocytes and the habenular/pretectal region suggesting direct pineal-brain communication. Control of melatonin biosynthesis in rodents involves transcriptional regulation including phosphorylation of CREB and upregulation of mPer1. In the SCN, melatonin acts upon MT1 and MT2 receptors. Melatonin is not necessary to maintain the rhythm of the SCN molecular clockwork, but it has distinct effects on the synchronization of the circadian rhythm by light, facilitates re-entrainment of the circadian system to phase advances in the level of the SCN molecular clockwork by acting upon MT2 receptors and plays a stabilizing role in the circadian system as evidenced from locomotor activity recordings. While the effects in the SCN are subtle, melatonin is essential for PT functions. Via the MT1 receptor it drives the PT-intrinsic molecular clockwork and the retrograde and anterograde output pathways controlling seasonal rhythmicity. Although inbred and transgenic mice do not show seasonal reproduction, the pathways from the PT are fully intact if the animals are melatonin proficient. Thus, only melatonin-proficient strains are suited to investigate the circadian and melatoninergic systems.

The relations between chronotype, stressful life events, and impulsivity in the Adolescent Brain Cognitive Development (ABCD) study

Circadian rhythm disturbances, especially circadian phase delays are associated with impulsive behaviors and have been implicated in psychiatric disorders. Chronotype is a developmentally regulated proxy measure of circadian phase. Past studies have investigated the relationship between chronotype and trauma and found that trauma is associated with evening chronotypes, suggesting the course of chronotype development may be affected by adverse childhood experiences (ACEs). However, the relationships among chronotype, impulsivity and ACEs have largely been studied in a pairwise manner using small, cross-sectional cohorts. We hypothesized that in a cohort of high-risk youth, childhood trauma would be associated with later chronotype, and later chronotype would be associated with higher rates of impulsivity. We analyzed a cross-sectional sample (n = 966) from Year 2 of adolescents at high risk for psychiatric disorders from the ABCD study who were characterized for chronotype, stressful life events, and impulsivity. We used a hierarchical regression model to examine the relationship between chronotype, stressful life events, and impulsivity using the Munich Chronotype Questionnaire (MCTQ), the Life Events Scale, Urgency, Premeditation, Perseverance and Sensation Seeking (UPPS) Impulsive Behavior scale. We found associations between eveningness, stressful life events, and all dimensions of impulsivity. Increased eveningness was associated with a higher number of stressful life events and increased impulsivity. Understanding the role of stressful life events and impulsivity in those predisposed towards eveningness is useful because it may improve our understanding of the biological mechanisms that contribute to psychiatric disorders, and lead to better prevention and treatment efforts using interventions such as increased lifestyle regularity and daytime light exposure.

Neurobiological and behavioral mechanisms of circadian rhythm disruption in bipolar disorder: A critical multi-disciplinary literature review and agenda for future research from the ISBD task force on chronobiology

AIM

Symptoms of bipolar disorder (BD) include changes in mood, activity, energy, sleep, and appetite. Since many of these processes are regulated by circadian function, circadian rhythm disturbance has been examined as a biological feature underlying BD. The International Society for Bipolar Disorders Chronobiology Task Force (CTF) was commissioned to review evidence for neurobiological and behavioral mechanisms pertinent to BD.

METHOD

Drawing upon expertise in animal models, biomarkers, physiology, and behavior, CTF analyzed the relevant cross-disciplinary literature to precisely frame the discussion around circadian rhythm disruption in BD, highlight key findings, and for the first time integrate findings across levels of analysis to develop an internally consistent, coherent theoretical framework.

RESULTS

Evidence from multiple sources implicates the circadian system in mood regulation, with corresponding associations with BD diagnoses and mood-related traits reported across genetic, cellular, physiological, and behavioral domains. However, circadian disruption does not appear to be specific to BD and is present across a variety of high-risk, prodromal, and syndromic psychiatric disorders. Substantial variability and ambiguity among the definitions, concepts and assumptions underlying the research have limited replication and the emergence of consensus findings.

CONCLUSIONS

Future research in circadian rhythms and its role in BD is warranted. Well-powered studies that carefully define associations between BD-related and chronobiologically-related constructs, and integrate across levels of analysis will be most illuminating.

Toward a Digital Future in Bipolar Disorder Assessment: A Systematic Review of Disruptions in the Rest-Activity Cycle as Measured by Actigraphy

BACKGROUND

Disruptions in rest and activity patterns are core features of bipolar disorder (BD). However, previous methods have been limited in fully characterizing the patterns. There is still a need to capture dysfunction in daily activity as well as rest patterns in order to more holistically understand the nature of 24-h rhythms in BD. Recent developments in the standardization, processing, and analyses of wearable digital actigraphy devices are advancing longitudinal investigation of rest-activity patterns in real time. The current systematic review aimed to summarize the literature on actigraphy measures of rest-activity patterns in BD to inform the future use of this technology.

METHODS

A comprehensive systematic review using PRISMA guidelines was conducted through PubMed, MEDLINE, PsycINFO, and EMBASE databases, for papers published up to February 2021. Relevant articles utilizing actigraphy measures were extracted and summarized. These papers contributed to three research areas addressed, pertaining to the nature of rest-activity patterns in BD, and the effects of therapeutic interventions on these patterns.

RESULTS

Seventy articles were included. BD was associated with longer sleep onset latency and duration, particularly during depressive episodes and with predictive value for worsening of future manic symptoms. Lower overall daily activity was also associated with BD, especially during depressive episodes, while more variable activity patterns within a day were seen in mania. A small number of studies linked these disruptions with differential patterns of brain functioning and cognitive impairments, as well as more adverse outcomes including increased suicide risk. The stabilizing effect of therapeutic options, including pharmacotherapies and chronotherapies, on activity patterns was supported.

CONCLUSION

The use of actigraphy provides valuable information about rest-activity patterns in BD. Although results suggest that variability in rhythms over time may be a specific feature of BD, definitive conclusions are limited by the small number of studies assessing longitudinal changes over days. Thus, there is an urgent need to extend this work to examine patterns of rhythmicity and regularity in BD. Actigraphy research holds great promise to identify a much-needed specific phenotypic marker for BD that will aid in the development of improved detection, treatment, and prevention options.

Heritability of Sleep and Its Disorders in Childhood and Adolescence

Purpose of Review

This review summarizes recent literature on the heritability of sleep and sleep disorders in childhood and adolescence. We also identify gaps in the literature and priorities for future research.

Recent Findings

Findings indicate that age, measurement method, reporter, and timing of sleep measurements can influence heritability estimates. Recent genome-wide association studies (GWAS) have identified differences in the heritability of sleep problems when ancestral differences are considered, but sample sizes are small compared to adult GWAS. Most studies focus on sleep variables in the full range rather than on disorder. Studies using objective measures of sleep typically comprised small samples.

Summary

Current evidence demonstrates a wide range of heritability estimates across sleep phenotypes in childhood and adolescence, but research in larger samples, particularly using objective sleep measures and GWAS, is needed. Further understanding of environmental mechanisms and the interaction between genes and environment is key for future research.

Real-time mobile monitoring of bipolar disorder: a review of evidence and future directions

Rapidly accumulating data from mobile assessments are facilitating our ability to track patterns of emotions, behaviors, biologic rhythms, and their contextual influences in real time. These approaches have been widely applied to study the core features, traits, changes in states, and the impact of treatments in bipolar disorder (BD). This paper reviews recent evidence on the application of both passive and active mobile technologies to gain insight into the role of the circadian system and patterns of sleep and motor activity in people with BD. Findings of more than two dozen studies converge in demonstrating a broad range of sleep disturbances, particularly longer duration and variability of sleep patterns, lower average and greater variability of motor activity, and a shift to later peak activity and sleep midpoint, indicative of greater evening orientation among people with BD. The strong associations across the domains tapped by real-time monitoring suggest that future research should shift focus on sleep, physical/motor activity, or circadian patterns to identify common biologic pathways that influence their interrelations. The development of novel data-driven functional analytic tools has enabled the derivation of individualized multilevel dynamic representations of rhythms of multiple homeostatic regulatory systems. These multimodal tools can inform clinical research through identifying heterogeneity of the manifestations of BD and provide more objective indices of treatment response in real-world settings. Collaborative efforts with common protocols for the application of multimodal sensor technology will facilitate our ability to gain deeper insight into mechanisms and multisystem dynamics, as well as environmental, physiologic, and genetic correlates of BD.

The Pennsylvania Longitudinal Study of Parents and Children (PALSPAC) Twin Registry

The Pennsylvania Longitudinal Study of Parents and Children Twin Registry was developed to capture a representative sample of multiple births and their parents in the state of Pennsylvania. The registry has two main efforts. The first began in 2012 through recruitment of adolescents in Pennsylvania schools. The second effort began in January 2019 in partnership with the Pennsylvania Department of Health to capture the birth cohort of twins born from 2007 to 2017. Study recruitment, sample demographics, focus and measures are provided, as well as future directions.

Chronotype and Social Jetlag: A (Self-) Critical Review

The Munich ChronoType Questionnaire (MCTQ) has now been available for more than 15 years and its original publication has been cited 1240 times (Google Scholar, May 2019). Additionally, its online version, which was available until July 2017, produced almost 300,000 entries from all over the world (MCTQ database). The MCTQ has gone through several versions, has been translated into 13 languages, and has been validated against other more objective measures of daily timing in several independent studies. Besides being used as a method to correlate circadian features of human biology with other factors-ranging from health issues to geographical factors-the MCTQ gave rise to the quantification of old wisdoms, like "teenagers are late", and has produced new concepts, like social jetlag. Some like the MCTQ's simplicity and some view it critically. Therefore, it is time to present a self-critical view on the MCTQ, to address some misunderstandings, and give some definitions of the MCTQ-derived chronotype and the concept of social jetlag.