A schizophrenic patient with an arrhythmic circadian rest-activity cycle

The circadian system: A neglected player in neurodevelopmental disorders

Patients with neurodevelopmental disorders, such as autism spectrum disorder, often display abnormal circadian rhythms. The role of the circadian system in these disorders has gained considerable attention over the last decades. Yet, it remains largely unknown how these disruptions occur and to what extent they contribute to the disorders' development. In this review, we examine circadian system dysregulation as observed in patients and animal models of neurodevelopmental disorders. Second, we explore whether circadian rhythm disruptions constitute a risk factor for neurodevelopmental disorders from studies in humans and model organisms. Lastly, we focus on the impact of psychiatric medications on circadian rhythms and the potential benefits of chronotherapy. The literature reveals that patients with neurodevelopmental disorders display altered sleep-wake cycles and melatonin rhythms/levels in a heterogeneous manner, and model organisms used to study these disorders appear to support that circadian dysfunction may be an inherent characteristic of neurodevelopmental disorders. Furthermore, the pre-clinical and clinical evidence indicates that circadian disruption at the environmental and genetic levels may contribute to the behavioural changes observed in these disorders. Finally, studies suggest that psychiatric medications, particularly those prescribed for attention-deficit/hyperactivity disorder and schizophrenia, can have direct effects on the circadian system and that chronotherapy may be leveraged to offset some of these side effects. This review highlights that circadian system dysfunction is likely a core pathological feature of neurodevelopmental disorders and that further research is required to elucidate this relationship.

Fluoxetine Decreases Phagocytic Function via REV-ERBα in Microglia

Although fluoxetine (FLX) is a commonly used drug in psychiatric disorders, such as major depressive disorder, anxiety disorder, panic disorder, and obsessive-compulsive disorder, the mechanism by which FLX exerts its therapeutic effect is not completely understood. In this study, we aimed to determine the possible mechanism by which FLX focuses on microglial phagocytosis. FLX reduced phagocytic function in BV2 cells and increased REV-ERBα without affecting other microglia-related genes, such as inflammation and phagocytosis. Although FLX did not change BMAL1 protein levels, it restricted the nucleocytoplasmic transport (NCT) of BMAL1, leading to its cytosolic accumulation. REV-ERBα antagonist SR8278 rescued the decreased phagocytic activity and restricted NCT of BMAL1. We also found that REV-ERBα mediates the effect of FLX via the inhibition of phospho-ERK (pERK). The ERK inhibitor FR180204 was sufficient to reduce phagocytic function in BV2 cells and restrict the NCT of BMAL1. These results were recapitulated in the primary microglia. In conclusion, we propose that FLX decreases phagocytic function and restricts BMAL1 NCT via REV-ERBα. In addition, ERK inhibition mimics the effects of FLX on microglia.

Psychotropic Drug Effects on Steroid Stress Hormone Release and Possible Mechanisms Involved

There is no doubt that chronic stress accompanied by adrenocortical stress hormone release affects the development and treatment outcome of several mental disorders. Less attention has been paid to the effects of psychotropic drugs on adrenocortical steroids, particularly in clinical studies. This review focuses on the knowledge related to the possible modulation of cortisol and aldosterone secretion under non-stress and stress conditions by antipsychotic drugs, which are being used in the treatment of several psychotic and affective disorders. The molecular mechanisms by which antipsychotic drugs may influence steroid stress hormones include the modulation of central and/or adrenocortical dopamine and serotonin receptors, modulation of inflammatory cytokines, influence on regulatory mechanisms in the central part of the hypothalamic-pituitary axis, inhibition of corticotropin-releasing hormone gene promoters, influencing glucocorticoid receptor-mediated gene transcription, indirect effects via prolactin release, alteration of signaling pathways of glucocorticoid and mineralocorticoid actions. Clinical studies performed in healthy subjects, patients with psychosis, and patients with bipolar disorder suggest that single and repeated antipsychotic treatments either reduce cortisol concentrations or do not affect its secretion. A single and potentially long-term treatment with dopamine receptor antagonists, including antipsychotics, has a stimulatory action on aldosterone release.

Effects of antipsychotics on circadian rhythms in humans: a systematic review and meta-analysis

Antipsychotics are widely used to treat psychiatric illness and insomnia. However, the etiology of insomnia is multifactorial, including disrupted circadian rhythms. Several studies show that antipsychotics might modulate even healthy circadian rhythms. The purpose of this systematic review is to integrate current knowledge about the effects of antipsychotics on the circadian rhythms in humans, and to conduct a meta- analysis with the available data. Nine electronic databases were searched. We followed the PRISMA guidelines and included randomized controlled trials (RCTs), non-RCTs, case-control studies, case series, and case reports. Of 7,217 articles, 70 were included. The available data was mainly from healthy individuals, or patients having schizophrenia, but the findings showed a transdiagnostic impact on circadian parameters. This was consistently seen as decreased amplitude of cortisol, melatonin, and body temperature. Particularly, a meta-analysis of 16 RCTs measuring cortisol rhythm showed that antipsychotics, especially atypical antipsychotics, decreased the cortisol area under the curve and morning cortisol level, compared to placebo. The data with melatonin or actigraphy was limited. Overall, this evidence about the circadian effect of antipsychotics showed a need for longitudinal, real-time monitoring of specific circadian markers to differentiate a change in amplitude from a shift in phasing, and for knowledge about optimal timing of administration of antipsychotics, according to individual baseline circadian parameters. Standardizing selection criteria and outcome methods could facilitate good quality intervention studies and evidence-based treatment guidelines. This is relevant considering the accumulating evidence of the high prevalence and unfavorable impact of disrupted circadian rhythms in psychiatric disorders.

Prevalence of Circadian Rhythm Sleep-Wake Disorder in Outpatients with Schizophrenia and Its Association with Psychopathological Characteristics and Psychosocial Functioning

The prevalence of circadian rhythm sleep-wake disorder (CRSWD) among patients with schizophrenia is not clear. The effect of comorbid CRSWD on such patients has also not been fully evaluated yet. Outpatients with schizophrenia in the maintenance phase who visited Tokyo Women’s Medical University Hospital between April 2018 and March 2019 participated in this study. The Brief Psychiatric Rating Scale (BPRS), the Clinical Global Impressions–Severity Illness Scale (CGI-S), Global Assessment of Functioning (GAF), World Health Organization Disability Assessment Schedule II, Insomnia Severity Index (ISI), and Morningness–Eveningness Questionnaire (MEQ) were administered, and the patient responses with and without CRSWD were compared. Of the 105 patients with schizophrenia, 19 (18.1%) had CRSWD. There were trends toward higher BPRS and lower GAF scores in the CRSWD group than in the non-CRSWD group, although these did not reach statistical significance following a false discovery rate correction. Among the BPRS subitems, the anxiety scores were significantly higher in the CRSWD group than in the non-CRSWD group (p < 0.01). CRSWD was highly prevalent among patients with schizophrenia in the maintenance phase. Comorbidities of CRSWD may affect psychopathological characteristics and psychosocial functioning.

Disrupted circadian rhythms and mental health

During the evolution of life, the temporal rhythm of our rotating planet was internalized in the form of circadian rhythms. Circadian rhythms are ~24h internal manifestations that drive daily patterns of physiology and behavior. These rhythms are entrained (synchronized) to the external environment, primarily by the light-dark cycle, and precisely controlled via molecular clocks located within the suprachiasmatic nucleus of the hypothalamus. Misalignment and/or disruption of circadian rhythms can have detrimental consequences for human health. Indeed, studies suggest strong associations between mental health and circadian rhythms. However, direct interactions between mood regulation and the circadian system are just beginning to be uncovered and appreciated. This chapter examines the relationship between disruption of circadian rhythms and mental health. The primary focus will be outlining the association between circadian disruption, in the form of night shift work, exposure to light at night, jet lag, and social jet lag, and psychiatric illness (i.e., anxiety, major depressive disorder, bipolar disorder, and schizophrenia). Additionally, we review animal models of disrupted circadian rhythms, which provide further evidence in support of a strong association between circadian disruption and affective responses. Finally, we discuss future directions for the field and suggest areas of study that require further investigation.

Disrupted Sleep and Circadian Rhythms in Schizophrenia and Their Interaction With Dopamine Signaling

Sleep and circadian rhythm disruption (SCRD) is a common feature of schizophrenia, and is associated with symptom severity and patient quality of life. It is commonly manifested as disturbances to the sleep/wake cycle, with sleep abnormalities occurring in up to 80% of patients, making it one of the most common symptoms of this disorder. Severe circadian misalignment has also been reported, including non-24 h periods and phase advances and delays. In parallel, there are alterations to physiological circadian parameters such as body temperature and rhythmic hormone production. At the molecular level, alterations in the rhythmic expression of core clock genes indicate a dysfunctional circadian clock. Furthermore, genetic association studies have demonstrated that mutations in several clock genes are associated with a higher risk of schizophrenia. Collectively, the evidence strongly suggests that sleep and circadian disruption is not only a symptom of schizophrenia but also plays an important causal role in this disorder. The alterations in dopamine signaling that occur in schizophrenia are likely to be central to this role. Dopamine is well-documented to be involved in the regulation of the sleep/wake cycle, in which it acts to promote wakefulness, such that elevated dopamine levels can disturb sleep. There is also evidence for the influence of dopamine on the circadian clock, such as through entrainment of the master clock in the suprachiasmatic nuclei (SCN), and dopamine signaling itself is under circadian control. Therefore dopamine is closely linked with sleep and the circadian system; it appears that they have a complex, bidirectional relationship in the pathogenesis of schizophrenia, such that disturbances to one exacerbate abnormalities in the other. This review will provide an overview of the evidence for a role of SCRD in schizophrenia, and examine the interplay of this with altered dopamine signaling. We will assess the evidence to suggest common underlying mechanisms in the regulation of sleep/circadian rhythms and the pathophysiology of schizophrenia. Improvements in sleep are associated with improvements in symptoms, along with quality of life measures such as cognitive ability and employability. Therefore the circadian system holds valuable potential as a new therapeutic target for this disorder.

Circadian rhythm disruption and mental health

Circadian rhythms are internal manifestations of the solar day that permit adaptations to predictable environmental temporal changes. These ~24-h rhythms are controlled by molecular clockworks within the brain that are reset daily to precisely 24 h by exposure to the light-dark cycle. Information from the master clock in the mammalian hypothalamus conveys temporal information to the entire body via humoral and neural communication. A bidirectional relationship exists between mood disorders and circadian rhythms. Mood disorders are often associated with disrupted circadian clock-controlled responses, such as sleep and cortisol secretion, whereas disruption of circadian rhythms via jet lag, night-shift work, or exposure to artificial light at night, can precipitate or exacerbate affective symptoms in susceptible individuals. Evidence suggests strong associations between circadian rhythms and mental health, but only recently have studies begun to discover the direct interactions between the circadian system and mood regulation. This review provides an overview of disrupted circadian rhythms and the relationship to behavioral health and psychiatry. The focus of this review is delineating the role of disruption of circadian rhythms on mood disorders using human night shift studies, as well as jet lag studies to identify links. We also review animal models of disrupted circadian rhythms on affective responses. Lastly, we propose low-cost behavioral and lifestyle changes to improve circadian rhythms and presumably behavioral health.

Mitochondria, Metabolism, and Redox Mechanisms in Psychiatric Disorders

Significance: Our current knowledge of the pathophysiology and molecular mechanisms causing psychiatric disorders is modest, but genetic susceptibility and environmental factors are central to the etiology of these conditions. Autism, schizophrenia, bipolar disorder and major depressive disorder show genetic gene risk overlap and share symptoms and metabolic comorbidities. The identification of such common features may provide insights into the development of these disorders. Recent Advances: Multiple pieces of evidence suggest that brain energy metabolism, mitochondrial functions and redox balance are impaired to various degrees in psychiatric disorders. Since mitochondrial metabolism and redox signaling can integrate genetic and environmental environmental factors affecting the brain, it is possible that they are implicated in the etiology and progression of psychiatric disorders. Critical Issue: Evidence for direct links between cellular mitochondrial dysfunction and disease features are missing. Future Directions: A better understanding of the mitochondrial biology and its intracellular connections to the nuclear genome, the endoplasmic reticulum and signaling pathways, as well as its role in intercellular communication in the organism, is still needed. This review focuses on the findings that implicate mitochondrial dysfunction, the resultant metabolic changes and oxidative stress as important etiological factors in the context of psychiatric disorders. We also propose a model where specific pathophysiologies of psychiatric disorders depend on circuit-specific impairments of mitochondrial dysfunction and redox signaling at specific developmental stages.

Evidence for an association of serum melatonin concentrations with recognition and circadian preferences in patients with schizophrenia

Melatonin, a neuro-differentiation factor, may play a role in the neurodevelopmental origins of schizophrenia. Cognitive impairment and decreased melatonin are reported in schizophrenia; however, the relationship between them remains unclear. We hypothesised that patients with schizophrenia would have lower concentrations of circulating melatonin than healthy controls and that melatonin levels would be associated with cognitive impairment. This study included 47 patients with schizophrenia and 40 healthy controls (HC). Serum melatonin concentrations were measured using the enzyme-linked immunosorbent assay. Positive and Negative Syndrome Scales (PANSS), The Morningness-Eveningness Questionnaire (MEQ), Pittsburgh Sleep Quality Index (PSQI), the Stroop and Oktem verbal memory processes (VMPT) tests were applied. Patients with schizophrenia had lower levels of melatonin compared to the HC group (p = 0.016), also after controlling for age, sex, and body mass index (BMI) (p = 0.024). In patients with schizophrenia, melatonin concentrations were associated with higher BMI (rho = 0.34, p = 0.01) and lower MEQ score (rho = -0.29, p = 0.035). The patient sample was split into low and high melatonin categories by using the median melatonin concentration in HC as the cut-off. Patients in the low melatonin group had poorer performance in VMPT-Recognition (p = 0.026) and Stroop-Colour Error (p = 0.032). Notwithstanding its limitations, the findings of this exploratory study suggest that decreased serum melatonin concentrations observed in schizophrenia might also be associated with cognitive impairment and circadian preferences. Future studies are required to investigate the role of melatonergic pathways in patients with schizophrenia.

Joint analysis of cognitive and circadian variation in Schizophrenia and Bipolar I Disorder

BACKGROUND

Impairment in cognitive variables and alterations in circadian function have been documented among patients with schizophrenia (SZ) and bipolar I disorder (BP1), but it is not known whether joint analysis of these variables can define clinically relevant sub-groups in either disorder.

OBJECTIVES

To evaluate the pattern and relationship of cognitive and circadian function in SZ and BP1 patients with respect to diagnosis and indices of clinical severity.

METHODS

Among patients with SZ and BP1, cognitive function was evaluated using the Penn Computerized Neurocognitive Battery and circadian function was assessed using the Composite Scale of Morningness/ Eveningness (CSM). Clinical severity was estimated using the Global Assessment of Function (GAF) scale, and age at onset of illness (AAO). The patients were compared with community based non-psychotic control individuals and non-psychotic first degree relatives of the SZ patients. The cluster distributions of cognitive function, circadian function and clinical severity were investigated and identified clusters compared across diagnostic groups.

RESULTS

Across participants, the cognitive domains could be separated into two clusters. Cluster 1 included the majority of control individuals and non-psychotic relatives, while SZ patients predominated in Cluster 2. BP1 patients were distributed across both clusters. The clusters could be differentiated by GAF scores, but not AAO. CSM scores were not significantly correlated with individual cognitive domains or with the clusters.

CONCLUSIONS

Clusters based on levels of cognitive function can discriminate SZ patients from control individuals, but not BP1 patients. CSM scores do not contribute to such discrimination.

Capturing Rest-Activity Profiles in Schizophrenia Using Wearable and Mobile Technologies: Development, Implementation, Feasibility, and Acceptability of a Remote Monitoring Platform

Background

There is growing interest in the potential for wearable and mobile devices to deliver clinically relevant information in real-world contexts. However, there is limited information on their acceptability and barriers to long-term use in people living with psychosis.

Objective

This study aimed to describe the development, implementation, feasibility, acceptability, and user experiences of the Sleepsight platform, which harnesses consumer wearable devices and smartphones for the passive and unobtrusive capture of sleep and rest-activity profiles in people with schizophrenia living in their homes.

Methods

A total of 15 outpatients with a diagnosis of schizophrenia used a consumer wrist-worn device and smartphone to continuously and remotely gather rest-activity profiles over 2 months. Once-daily sleep and self-rated symptom diaries were also collected via a smartphone app. Adherence with the devices and smartphone app, end-of-study user experiences, and agreement between subjective and objective sleep measures were analyzed. Thresholds for acceptability were set at a wear time or diary response rate of 70% or greater.

Results

Overall, 14 out of 15 participants completed the study. In individuals with a mild to moderate symptom severity at baseline (mean total Positive and Negative Syndrome Scale score 58.4 [SD 14.4]), we demonstrated high rates of engagement with the wearable device (all participants meeting acceptability criteria), sleep diary, and symptom diary (93% and 86% meeting criteria, respectively), with negative symptoms being associated with lower diary completion rate. The end-of-study usability and acceptability questionnaire and qualitative analysis identified facilitators and barriers to long-term use, and paranoia with study devices was not a significant barrier to engagement. Comparison between sleep diary and wearable estimated sleep times showed good correspondence (ρ=0.50, P<.001).

Conclusions

Extended use of wearable and mobile technologies are acceptable to people with schizophrenia living in a community setting. In the future, these technologies may allow predictive, objective markers of clinical status, including early markers of impending relapse.

Influence of Schizophrenia-Associated Gene Egr3 on Sleep Behavior and Circadian Rhythms in Mice

Up to 80% of people meeting DSM-IV definitions for schizophrenia will exhibit difficulties with sleep, along with a breakdown in circadian entrainment and rhythmicity. The changes to the sleep and circadian systems in this population are thought to be interdependent, as evidenced by the frequent use of the combined term "sleep and circadian rhythm disruption" or "SCRD" to describe their occurrence. To understand links between sleep and circadian problems in the schizophrenia population, we analyzed the duration and rhythmicity of sleep behavior in mice lacking function of the immediate early gene early growth response 3 ( Egr3). EGR3 has been associated with schizophrenia risk in humans, and Egr3-deficient (-/-) mice display various features of schizophrenia that are responsive to antipsychotic treatment. While Egr3-/- mice slept less than their wildtype (WT) littermates, they showed no evidence of circadian disorganization; in fact, circadian rhythms of activity were more robust in these mice compared with WT, as measured by time series analysis and the relative amplitude index of Van Someren's suite of non-parametric circadian rhythm analyses. Differences in circadian robustness were maintained when the animals were transferred to several weeks of housing under constant darkness or constant light. Together, our results suggest that Egr3-/- mice retain control over the circadian timekeeping of sleep and wake, while showing impaired sleep. The findings are compatible with those from a surprising array of mouse models of schizophrenia and raise the possibility that SCRD may be 2 separate disorders in the schizophrenia population requiring different treatment strategies.

The Circadian Clock and Human Health

Epidemiological studies provided the first evidence suggesting a connection between the circadian clock and human health. Mutant mice convincingly demonstrate the principle that dysregulation of the circadian system leads to a multitude of pathologies. Chrono-medicine is one of the most important upcoming themes in the field of circadian biology. Although treatments counteracting circadian dysregulation are already being applied (e.g., prescribing strong and regular zeitgebers), we need to comprehend entrainment throughout the body's entire circadian network before understanding the mechanisms that tie circadian dysregulation to pathology. Here, we attempt to provide a systematic approach to understanding the connection between the circadian clock and health. This taxonomy of (mis)alignments on one hand exposes how little we know about entrainment within any organism and which 'eigen-zeitgeber' signals are used for entrainment by the different cells and tissues. On the other hand, it provides focus for experimental approaches and tools that will logically map out how circadian systems contribute to disease as well as how we can treat and prevent them.

Schizophrenia: the role of sleep and circadian rhythms in regulating dopamine and psychosis

Schizophrenia has long been associated with abnormalities in circadian rhythms and sleep. Up until now, there have been no thorough reviews of the potential mechanisms behind the myriad of circadian and sleep abnormalities observed in schizophrenia and psychosis. We present evidence of sleep playing an important role in psychosis predominantly mediated by dopaminergic pathways. A synthesis of both human and animal experimental work suggests that the interplay between sleep and dopamine is important in the generation and maintenance of psychosis. In particular, both animal and human data point to sleep disruption increasing dopamine release and sensitivity. Furthermore, elevated dopamine levels disrupt sleep and circadian rhythms. The synthesis of knowledge suggests that circadian rhythms, dopamine dysregulation, and psychosis are intricately linked. This suggests that treatment of circadian disturbance may be a useful target in improving the lives and symptoms of patients with schizophrenia.

Altered circadian clock gene expression in patients with schizophrenia

Impaired circadian rhythmicity has been reported in several psychiatric disorders. Schizophrenia is commonly associated with aberrant sleep-wake cycles and insomnia. It is not known if schizophrenia is associated with disturbances in molecular rhythmicity. We cultured fibroblasts from skin samples obtained from patients with chronic schizophrenia and from healthy controls, respectively, and analyzed the circadian expression during 48h of the clock genes CLOCK, BMAL1, PER1, PER2, CRY1, CRY2, REV-ERBα and DBP. In fibroblasts obtained from patients with chronic schizophrenia, we found a loss of rhythmic expression of CRY1 and PER2 compared to cells from healthy controls. We also estimated the sleep quality in these patients and found that most of them suffered from poor sleep in comparison with the healthy controls. In another patient sample, we analyzed mononuclear blood cells from patients with schizophrenia experiencing their first episode of psychosis, and found decreased expression of CLOCK, PER2 and CRY1 compared to blood cells from healthy controls. These novel findings show disturbances in the molecular clock in schizophrenia and have important implications in our understanding of the aberrant rhythms reported in this disease.

The two-process model of sleep regulation: a reappraisal

In the last three decades the two-process model of sleep regulation has served as a major conceptual framework in sleep research. It has been applied widely in studies on fatigue and performance and to dissect individual differences in sleep regulation. The model posits that a homeostatic process (Process S) interacts with a process controlled by the circadian pacemaker (Process C), with time-courses derived from physiological and behavioural variables. The model simulates successfully the timing and intensity of sleep in diverse experimental protocols. Electrophysiological recordings from the suprachiasmatic nuclei (SCN) suggest that S and C interact continuously. Oscillators outside the SCN that are linked to energy metabolism are evident in SCN-lesioned arrhythmic animals subjected to restricted feeding or methamphetamine administration, as well as in human subjects during internal desynchronization. In intact animals these peripheral oscillators may dissociate from the central pacemaker rhythm. A sleep/fast and wake/feed phase segregate antagonistic anabolic and catabolic metabolic processes in peripheral tissues. A deficiency of Process S was proposed to account for both depressive sleep disturbances and the antidepressant effect of sleep deprivation. The model supported the development of novel non-pharmacological treatment paradigms in psychiatry, based on manipulating circadian phase, sleep and light exposure. In conclusion, the model remains conceptually useful for promoting the integration of sleep and circadian rhythm research. Sleep appears to have not only a short-term, use-dependent function; it also serves to enforce rest and fasting, thereby supporting the optimization of metabolic processes at the appropriate phase of the 24-h cycle.

A highly tunable dopaminergic oscillator generates ultradian rhythms of behavioral arousal

Ultradian (∼4 hr) rhythms in locomotor activity that do not depend on the master circadian pacemaker in the suprachiasmatic nucleus have been observed across mammalian species, however, the underlying mechanisms driving these rhythms are unknown. We show that disruption of the dopamine transporter gene lengthens the period of ultradian locomotor rhythms in mice. Period lengthening also results from chemogenetic activation of midbrain dopamine neurons and psychostimulant treatment, while the antipsychotic haloperidol has the opposite effect. We further reveal that striatal dopamine levels fluctuate in synchrony with ultradian activity cycles and that dopaminergic tone strongly predicts ultradian period. Our data indicate that an arousal regulating, dopaminergic ultradian oscillator (DUO) operates in the mammalian brain, which normally cycles in harmony with the circadian clock, but can desynchronize when dopamine tone is elevated, thereby producing aberrant patterns of arousal which are strikingly similar to perturbed sleep-wake cycles comorbid with psychopathology.

DOI:http://dx.doi.org/10.7554/eLife.05105.001

The sleep-wake cycle of mammals is controlled by a ‘circadian clock’ within the brain, which is synchronized to the day–night cycle. However, other aspects of mammalian physiology including alertness and activity levels, as well as appetite and body temperature—fluctuate in cycles that repeat every few hours. These cycles are known as ultradian rhythms, and they may offer survival benefits by enabling potentially risky behaviors, such as foraging, to be coordinated between members of a group.

Despite their widespread nature and the fact that they appear to be conserved in evolution, virtually nothing is known about the molecular basis of ultradian rhythms. Blum et al. have now identified a second internal clock within the brain, which they name ‘the DUO’, and shown that this clock normally works in concert with the circadian clock to regulate daily patterns of activity and alertness.

Experiments in mice revealed that the DUO uses the brain chemical dopamine to generate bursts of activity roughly every four hours. Moreover, it continues to work when the circadian clock has been destroyed. Measurements of dopamine in freely moving mice showed that levels of the chemical fluctuate in synchrony with the animals' activity levels. Moreover, drugs that flood the brain with dopamine, such as methamphetamine, disrupt the 4-hour cycle by lengthening the period between bursts of activity, whereas drugs that block dopamine receptors have the opposite effect.

As well as revealing a mechanism by which the brain coordinates processes that repeat several times per day, the identification of the DUO could also provide insights into the biological basis of psychiatric disorders. Conditions such as schizophrenia and bipolar disorder are often accompanied by disturbances in patterns of activity and rest. While these have previously been attributed to the disruption of circadian rhythms, there is little direct evidence for this, which raises the possibility that these changes might instead reflect the disruption of ultradian rhythms.

DOI:http://dx.doi.org/10.7554/eLife.05105.002

Circadian Activity Rhythms and Sleep in Nurses Working Fixed 8-hr Shifts

Shift work is associated with adverse health outcomes. The aim of this study was to explore the effects of shift work on circadian activity rhythms (CARs) and objective and subjective sleep quality in nurses. Female day-shift (n = 16), evening-shift (n = 6), and night-shift (n = 13) nurses wore a wrist actigraph to monitor the activity. We used cosinor analysis and time-frequency analysis to study CARs. Night-shift nurses exhibited the lowest values of circadian rhythm amplitude, acrophase, autocorrelation, and mean of the circadian relative power (CRP), whereas evening-shift workers exhibited the greatest standard deviation of the CRP among the three shift groups. That is, night-shift nurses had less robust CARs and evening-shift nurses had greater variations in CARs compared with nurses who worked other shifts. Our results highlight the importance of assessing CARs to prevent the adverse effects of shift work on nurses' health.

Effects of N-acetylcysteine and imipramine in a model of acute rhythm disruption in BALB/c mice

Circadian rhythm disturbances are among the risk factors for depression, but specific animal models are lacking. This study aimed to characterize the effects of acute rhythm disruption in mice and investigate the effects of imipramine and N-acetylcysteine (NAC) on rhythm disruption-induced changes. Mice were exposed to 12:12-hour followed by 10:10-hour light:dark cycles (LD); under the latter, mice were treated with saline, imipramine or NAC. Rhythms of rest/activity and temperature were assessed with actigraphs and iButtons, respectively. Hole-board and social preference tests were performed at the beginning of the experiment and again at the 8th 10:10 LD, when plasma corticosterone and IL-6 levels were also assessed. Actograms showed that the 10:10 LD schedule prevents the entrainment of temperature and activity rhythms for at least 13 cycles. Subsequent light regimen change activity and temperature amplitudes showed similar patterns of decline followed by recovery attempts. During the 10:10 LD schedule, activity and temperature amplitudes were significantly decreased (paired t test), an effect exacerbated by imipramine (ANOVA/SNK). The 10:10 LD schedule increased anxiety (paired t test), an effect prevented by NAC (30 mg/kg). This study identified mild but significant behavioral changes at specific time points after light regimen change. We suggest that if repeated overtime, these subtle changes may contribute to lasting behavioral disturbancess relevant to anxiety and mood disorders. Data suggest that imipramine may contribute to sustained rhythm disturbances, while NAC appears to prevent rhythm disruption-induced anxiety. Associations between sleep/circadian disturbances and the recurrence of depressive episodes underscore the relevance of potential drug-induced maintenance of disturbed rhythms.

Links between Circadian Rhythms and Psychiatric Disease

Determining the cause of psychiatric disorders is a goal of modern neuroscience, and will hopefully lead to the discovery of treatments to either prevent or alleviate the suffering caused by these diseases. One roadblock to attaining this goal is the realization that neuropsychiatric diseases are rarely due to a single gene polymorphism, environmental exposure, or developmental insult. Rather, it is a complex interaction between these various influences that likely leads to the development of clinically relevant syndromes. Our lab is exploring the links between environmental exposures and neurobehavioral function by investigating how disruption of the circadian (daily) clock alters the structure and function of neural circuits, with the hypothesis that disrupting this crucial homeostatic system can directly contribute to altered vulnerability of the organism to other factors that interact to produce psychiatric illness. This review explores some historical and more recent findings that link disrupted circadian clocks to neuropsychiatric disorders, particularly depression, mania, and schizophrenia. We take a comparative approach by exploring the effects observed in human populations, as well as some experimental models used in the laboratory to unravel mechanistic and causal relationships between disruption of the circadian clock and behavioral abnormalities. This is a rich area of research that we predict will contribute greatly to our understanding of how genes, environment, and development interact to modulate an individual’s vulnerability to psychiatric disorders.

Sleep and circadian rhythm dysregulation in schizophrenia

Sleep-onset and maintenance insomnia is a common symptom in schizophrenic patients regardless of either their medication status (drug-naive or previously treated) or the phase of the clinical course (acute or chronic). Regarding sleep architecture, the majority of studies indicate that non-rapid eye movement (NREM), N3 sleep and REM sleep onset latency are reduced in schizophrenia, whereas REM sleep duration tends to remain unchanged. Many of these sleep disturbances in schizophrenia appear to be caused by abnormalities of the circadian system as indicated by misalignments of the endogenous circadian cycle and the sleep-wake cycle. Circadian disruption, sleep onset insomnia and difficulties in maintaining sleep in schizophrenic patients could be partly related to a presumed hyperactivity of the dopaminergic system and dysfunction of the GABAergic system, both associated with core features of schizophrenia and with signaling in sleep and wake promoting brain regions. Since multiple neurotransmitter systems within the CNS can be implicated in sleep disturbances in schizophrenia, the characterization of the neurotransmitter systems involved remains a challenging dilemma.

Role of melatonin in schizophrenia

Schizophrenia is a chronic mental disease that disturbs several cognitive functions, such as memory, thought, perception and volition. Schizophrenia’s biological etiology is multifactorial and is still under investigation. Melatonin has been involved in schizophrenia since the first decades of the twentieth century. Research into melatonin regarding schizophrenia has followed two different approaches. The first approach is related to the use of melatonin as a biological marker. The second approach deals with the clinical applications of melatonin as a drug treatment. In this paper, both aspects of melatonin application are reviewed. Its clinical use in schizophrenia is emphasized.

Are cardiometabolic and endocrine abnormalities linked to sleep difficulties in schizophrenia? A hypothesis driven review

Schizophrenia is a psychiatric disorder that includes symptoms such as hallucinations, disordered thoughts, disorganized or catatonic behaviour, cognitive dysfunction and sleep-wake disturbance. In addition to these symptoms, cardiometabolic dysfunction is common in patients with schizophrenia. While previously it has been thought that cardiometabolic symptoms in patients with schizophrenia were associated with medications used to manage this disorder, more recently it has been demonstrated that these symptoms are present in drug naive and unmedicated patients. Sleep-wake disturbance, resulting in chronic sleep loss has also been demonstrated to induce changes in cardiometabolic function. Chronic sleep loss has been associated with an increased risk for weight gain, obesity and cardiac and metabolic disorders, independent of other potentially contributing factors, such as smoking and body mass index. We hypothesise that the sleep-wake disturbance comorbid with schizophrenia may play a significant role in the high prevalence of cardiometabolic dysfunction observed in this patient population. Here we present a critical review of the evidence that supports this hypothesis.

Sleep and circadian rhythm disruption in schizophrenia

BACKGROUND

Sleep disturbances comparable with insomnia occur in up to 80% of people with schizophrenia, but very little is known about the contribution of circadian coordination to these prevalent disruptions.

AIMS

A systematic exploration of circadian time patterns in individuals with schizophrenia with recurrent sleep disruption.

METHOD

We examined the relationship between sleep-wake activity, recorded actigraphically over 6 weeks, along with ambient light exposure and simultaneous circadian clock timing, by collecting weekly 48 h profiles of a urinary metabolite of melatonin in 20 out-patients with schizophrenia and 21 healthy control individuals matched for age, gender and being unemployed.

RESULTS

Significant sleep/circadian disruption occurred in all the participants with schizophrenia. Half these individuals showed severe circadian misalignment ranging from phase-advance/delay to non-24 h periods in sleep-wake and melatonin cycles, and the other half showed patterns from excessive sleep to highly irregular and fragmented sleep epochs but with normally timed melatonin production.

CONCLUSIONS

Severe circadian sleep/wake disruptions exist despite stability in mood, mental state and newer antipsychotic treatment. They cannot be explained by the individuals' level of everyday function.

Haloperidol alters circadian clock gene product expression in the mouse brain

OBJECTIVES

Circadian rhythms are patterns in behavioural and physiological measures that recur on a daily basis and are driven by an endogenous circadian timekeeping system whose molecular machinery consists of a number of clock genes. The typical anti-psychotic haloperidol has previously been shown to induce significant deficiencies in circadian timing in patients. In this study we examined the impact of haloperidol treatment on molecular components of the circadian clock in the mouse brain.

METHODS

We examined how haloperidol treatment, either acute (both at day and night) or chronically over 14 days, alters the expression of three clock gene protein products (PER1, PER2, BMAL1) across the mouse brain by means of immunohistochemistry.

RESULTS

Chronic haloperidol treatment significantly decreases the expression levels of PER1 in a number of brain areas, including the hippocampus, the prefrontal and cingulate cerebral cortex and the paraventricular nucleus of the hypothalamus. PER2 expression was only altered in the dentate gyrus and the CA3, and BMAL1 expression was only altered in the paraventricular nucleus of the hypothalamus.

CONCLUSION

These data indicate that haloperidol has the potential to alter circadian rhythms via modulation of circadian clock gene expression.

Sleep-wake cycles and cognitive functioning in schizophrenia

BACKGROUND

Irregular sleep-wake cycles and cognitive impairment are frequently observed in schizophrenia, however, how they interact remains unclear.

AIMS

To investigate the repercussions of circadian rhythm characteristics on cognitive performance and psychopathology in individuals with schizophrenia.

METHOD

Fourteen middle-aged individuals diagnosed with schizophrenia underwent continuous wrist actimetry monitoring in real-life settings for 3 weeks, and collected saliva samples to determine the onset of endogenous melatonin secretion as a circadian phase marker. Moreover, participants underwent multiple neuropsychological testing and clinical assessments throughout the study period.

RESULTS

Sleep-wake cycles in individuals with schizophrenia ranged from well entrained to highly disturbed rhythms with fragmented sleep epochs, together with delayed melatonin onsets and higher levels of daytime sleepiness. Participants with a normal rest-activity cycle (objectively determined by high relative amplitude of day/night activity) performed significantly better in frontal lobe function tasks. Stepwise regression analysis revealed that relative amplitude and age represented the best predictors for cognitive performance (Stroop colour-word interference task, Trail Making Test A and B, semantic verbal fluency task), whereas psychopathology (Positive and Negative Syndrome Scale) did not significantly correlate with either cognitive performance levels or the quality of sleep-wake cycles.

CONCLUSIONS

Consolidated circadian rhythms and sleep may be a prerequisite for adequate cognitive functioning in individuals with schizophrenia.

Sleep habits in middle-aged, non-hospitalized men and women with schizophrenia: a comparison with healthy controls

Patients with schizophrenia may have sleep disorders even when clinically stable under antipsychotic treatments. To better understand this issue, we measured sleep characteristics between 1999 and 2003 in 150 outpatients diagnosed with Diagnostic and Statistical Manual of Mental Disorders, fourth edition (DSM-IV) schizophrenia or schizoaffective disorder and 80 healthy controls using a sleep habits questionnaire. Comparisons between both groups were performed and multiple comparisons were Bonferroni corrected. Compared to healthy controls, patients with schizophrenia reported significantly increased sleep latency, time in bed, total sleep time and frequency of naps during weekdays and weekends along with normal sleep efficiency, sleep satisfaction, and feeling of restfulness in the morning. In conclusion, sleep-onset insomnia is a major, enduring disorder in middle-aged, non-hospitalized patients with schizophrenia that are otherwise clinically stable under antipsychotic and adjuvant medications. Noteworthy, these patients do not complain of sleep-maintenance insomnia but report increased sleep propensity and normal sleep satisfaction. These results may reflect circadian disturbances in schizophrenia, but objective laboratory investigations are needed to confirm subjective sleep reports.

The suitability of actigraphy, diary data, and urinary melatonin profiles for quantitative assessment of sleep disturbances in schizophrenia: A case report

Sleep disruption is a commonly encountered clinical feature in schizophrenic patients, and one important concern is to determine the extent of this disruption under "real" life situations. Simultaneous wrist actigraphy, diary records, and repeated urine collection for urinary 6-sulphatoxymelatonin (aMT6s) profiles are appropriate tools to assess circadian rhythms and sleep patterns in field studies. Their suitability for long-term recordings of schizophrenic patients living in the community has not been evaluated. In this case report, we document long-term simultaneous wrist actigraphy, light detection, repeated urine collection, and diary records as a suitable combination of non-invasive techniques to quantify and assess changes in sleep-wake cycles, light exposure, and melatonin profiles in a schizophrenic patient. The actigraph was well-tolerated by the patient, and compliance to diary records and 48 h urine collection was particularly good with assistance from family members. The data obtained by these techniques are illustrated, and the results reveal remarkable abnormal patterns of rest-activity patterns, light exposure, and melatonin production. We observed various rest-activity patterns, including phase-shifts, highly delayed sleep on- and offsets, and irregular rest-activity phases. The period of the rest-activity rhythm, light-dark cycle, and melatonin rhythm was longer than 24 h. These circadian abnormalities may reinforce the altered sleep patterns and the problems of cognitive function and social engagement associated with schizophrenic.

Dream content in chronically-treated persons with schizophrenia

Many clinical, laboratory and non-laboratory studies have examined dream content reported by patients with schizophrenia but findings have been variable and inconsistent. Using both questionnaire-based measures and laboratory REM sleep awakenings, we investigated dream content in 14 patients with schizophrenia (mean age=25.5+/-3.2 years) under atypical antipsychotic medication and 15 healthy controls (mean age=22.3+/-4.2 years). The relationship between eye movement density during REM sleep and dream content was also explored. Questionnaire data revealed that when compared to controls, patients with schizophrenia report experiencing a greater number of nightmares but no significant differences were found on other measures including overall dream recall, presence of recurrent dreams, and frequency of specific emotions. 39 dream reports were collected from each group following awakenings from REM sleep. Laboratory dream narratives from the patients were shorter and, after controlling for report length, most significant differences in dream content between the two groups disappeared with the exception of a greater proportion of unknown characters in the participant group. Patients with schizophrenia spontaneously rated their dream reports as being less bizarre than did controls, despite a similar density of bizarre elements as scored by external judges. Finally, both groups had a comparable density of rapid eye movements during REM sleep but a significant positive correlation between eye-movement density and dream content variables was only found in controls. Taken together, the findings suggest that dream content characteristics in schizophrenia may reflect neurocognitive processes, including emotional processing, specific to this disorder.

Delayed sleep phase in severe obsessive-compulsive disorder: a systematic case-report survey

INTRODUCTION

To study the prevalence of delayed sleep phase (DSP) in a cohort of inpatients with severe obsessive-compulsive disorder (OCD) and to identify clinical and demographic correlates.

METHODS

A systematic retrospective case-report study of consecutive OCD admissions to a specialist inpatient unit from January 1995 to December 2003. Nursing and medical records of sleep, demographic, clinical, and other relevant details were recorded.

RESULTS

Of 194 eligible consecutive case reports, 187 were located, and nursing and medical reports of sleep were identified in all 187 (100%). Thirty-three patients (17.6%) fulfilled operationally defined criteria for DSP after exclusion of possible confounding factors. All the patients with DSP were unemployed. Phase-shifted patients were significantly younger than non-shifted patients (P=.019) and reported an earlier age of onset of their OCD (P=.005). There was a non-significant trend toward more severe OCD in the phase-shifted group, but they were not more depressed than their non-shifted counterparts.

CONCLUSION

A substantial number of patients with severe, enduring OCD also suffer with DSP, which seems to be specifically linked to OCD as opposed to comorbid depression. Clarification of the etiology within DSP and its interaction with core OCD symptoms on clinical function and disability may identify new treatment targets. To this end, further studies of sleep in OCD using actigraphy and biological measures are indicated.

The role of circadian clock genes in mental disorders

The study of molecular clock mechanisms in psychiatric disorders is gaining significant interest due to data suggesting that a misalignment between the endogenous circadian system and the sleep-wake cycle might contribute to the clinical status of patients suffering from a variety of psychiatric disorders. Sleep disturbances in major depressive disorder (MDD) are characterized by increased sleep latency, poorer sleep efficiency, reduced latency to the first rapid eye movement (REM) sleep episode, and early-morning awakening, but there is little data to indicate a role of circadian clock genes in MDD. There is also relatively little information regarding the role of clock genes in anxiety. In contrast, a significant amount of evidence gathered in bipolar disorder (BPD) patients suggests a circadian rhythm disorder, namely an advanced circadian rhythm and state-dependent alterations of REM sleep latency. Most research on the role of clock genes in BPD has focused on polymorphisms of CLOCK, but the lithium target GSK3 may also play a significant role. A circadian phase shift is also theorized to contribute to the pathophysiology of winter seasonal affective disorder (SAD). Certain allelic combinations of NPAS2, PER3, and BMAL1 appear to contribute to the risk of SAD. In chronic shizophrenia, disturbances of sleep including insomnia and reduced sleep efficiency have been observed. Genetic studies have found associations with CLOCK, PER1, PER3, and TIMELESS. Sleep and circadian changes associated with dementia due to Alzheimer's disease suggest a functional change in the circadian master clock, which is supported by postmortem studies of clock gene expression in the brain.

Biological clocks and the practice of psychiatry

Endogenous biological clocks enable living species to acquire some independence in relation to time. They improve the efficiency of biological systems, by allowing them to anticipate future constraints on major physyological systems and cell energy metabolism. The temporal organization of a giwen biological function can be impaired in its coordination with astronomical time or with other biological function. There are also external conditions that influence biological clocks. This temporal organization is complex, and it is possible that a series of psychiatric disorders and syndromes involve primary or secondary changes in biological clocks: seasonal and other mood disorders, premenstrual syndromes, social jet lag, free-running rhythms, and several sleep disorders are among them. In this review, we describe the main concepts relevant to chronobiology and explore the relevance of knowledge about biological clocks to the clinical practice of psychiatry

Behavioral and psychiatric consequences of sleep-wake schedule disorders

Circadian rhythm sleep disorders (CRSDs) arise when an individual's sleep-wake rhythm mismatches the environmental 24-h schedule. Physiological data and genetic studies in patients with CRSDs suggest that these disorders result from abnormal functioning of the circadian timing system. Diagnosis involves recognition of the characteristics of CRSDs, which can be achieved by clinical interview and actigraphic monitoring of rest-activity patterns. Bright-light therapy and melatonin administration have proved to be the most effective treatment modalities of CRSDs. In psychiatric practice, CRSDs can be encountered on various occasions. Some evidence indicates that a deviant sleep-wake schedule might be a predisposing factor to personality disorders. CRSDs can emerge as an iatrogenic effect of certain psychoactive drugs, such as haloperidol and fluvoxamine. It is not uncommon that the daytime functional difficulties that accompany CRSDs are misinterpreted as symptoms of psychopathology. Recognition and awareness of these disorders should prevent years of erroneous diagnosis and treatment in these patients.

Older schizophrenia patients have more disrupted sleep and circadian rhythms than age-matched comparison subjects

Patient reports and laboratory studies suggest schizophrenia patients have disrupted sleep across age groups. Studies have not compared overall sleep/wake patterns or circadian (24-h) activity rhythms of older community dwelling schizophrenia patients to matched comparison subjects. This study examined whether older schizophrenia patients had more disrupted sleep/wake patterns and circadian activity rhythms than age- and gender-matched normal comparison subjects (NCS). Twenty-eight older schizophrenia patients and 28 age- and gender-matched NCS were studied with three days of continuous wrist actigraphy. Nighttime and daytime actigraphically estimated sleep and wake, circadian activity rhythms and light exposure patterns were compared with and without years of education as a covariate. Patients spent longer in bed, had more disrupted nighttime sleep, slept more during the day, and had less robust circadian rhythms of activity and light exposure compared to NCS. Differences persisted in education-adjusted analyses. Within patients, working was associated with improved sleep and circadian rhythms. Findings suggest the sleep and circadian rhythm disruption of older schizophrenia patients was more extensive than that of matched NCS suggesting patients' sleep disruption was above and beyond what is attributable to advanced age alone. A need exists to develop multicomponent interventions to address sleep difficulties specific to older schizophrenia patients.

Quality of sleep in patients with schizophrenia is associated with quality of life and coping

BACKGROUND

While sleep disturbance is widespread in schizophrenia it is less clear whether sleep disturbance is uniquely related to impaired coping and perceived quality of life.

METHODS

We simultaneously assessed sleep quality, symptoms, and coping in 29 persons with schizophrenia or schizoaffective disorder in a post acute phase of illness. Assessment instruments included the Pittsburgh Sleep Quality Index; the Positive and Negative Symptom Scale; the Heinrichs Quality of Life Scale; and the Ways of Coping Scale. Multiple regressions were performed predicting quality of life and coping from sleep quality controlling for age and symptom severity. On a subset of seven subjects non-dominant wrist actigraphy was used as an objective check of their self-reported poor sleep.

RESULTS

Analyses revealed that poor sleep quality predicted low quality of life (r = -0.493; p = .022) and reduced preference for employing positive reappraisal when facing a stressor (r = -0.0594; p = 0.0012). Actigraphy confirmed poor sleep quality in a subset of subjects. They had shorter sleep duration (p < .0005), shorter average sleep episodes (p < .005) and more episodes of long awakening (p < 0.05) than community norms.

CONCLUSION

The results are consistent with the hypotheses that poor sleep may play a unique role in sustaining poor quality of life and impaired coping in patients with schizophrenia. These associations may hold for community controls as well.

Pharmacological modulation of circadian rhythms: a new drug target in psychotherapeutics

Daily variation in an organism's physiology and behaviour is regulated by the synchrony that is achieved between the internal timing mechanisms - the circadian rhythms of the biological clock - and the prevailing environmental cues. Proper synchrony constitutes an adaptive response; improper or lost synchrony may well yield maladaptation and, in the case of humans, a psychiatric disorder. On a basic level, the circadian system is comprised of three parts: a central oscillator, its various neuronal inputs and its outputs. For all three of these parts, the dissemination of new information is moving at an unprecedented pace, and the number of molecular targets for the opportunistic pharmacologist is growing in step. Monoamines, neuropeptides, kinases - sorting through all these, much less developing one into a drug discovery programme, may be the biggest challenge. However, the potential benefits in targeting a basic flaw in a fundamental biological system may be enormous.

Changes in toxicity and effectiveness with timing of drug administration: implications for drug safety

The effectiveness and toxicity of many drugs can vary depending on the time of administration in relation to 24-hour rhythms of biochemical, physiological and behavioural processes under the control of the circadian clock. Such chronopharmacological phenomena are influenced by not only the pharmacokinetics but also pharmacodynamics of medications. Chronotherapy is especially relevant when the risk and/or intensity of the symptoms of disease vary predictably over time as exemplified by allergic rhinitis, arthritis, asthma, myocardial infarction, congestive heart failure, stroke and peptic ulcer disease. Morning, once-daily administration of corticosteroids results in little adrenocortical suppression, while the same daily dose split into four equal doses to coincide with daily meals and bedtime results in significant hypothalamus-pituitary-adrenal axis suppression. In a randomised, multicentre trial involving patients with previously untreated metastases from colorectal cancer, the chronomodulated infusion of oxaliplatin, fluorouracil and folinic acid was compared with a constant-rate infusion method. Adverse effects such as stomatitis and peripheral sensory neuropathy were lower and objective response was higher with chronotherapy as compared with the fixed-rate infusion. The merit of chronomodulated infusion is supported by the 24-hour rhythm of DNA synthesis and the activity of dehydropyrimidine dehydrogenase, which brings about the intracellular catabolism of fluorouracil. On the other hand, haloperidol and selective serotonin reuptake inhibitors have diverse effects on sleep continuity and nocturnal arousals. Although interferon also alters the clock function, this disruptive effect can be overcome by devising an administration regimen that minimises adverse drug effects on clock function. Thus, one approach to increasing the efficiency of pharmacotherapy is the administration of drugs at times at which they are most effective and/or best tolerated.

Temporal organization of the brain: Neurocognitive mechanisms and clinical implications

The synchrony between the individual brain and its environment is maintained by a system of internal clocks that together reflect the temporal organization of the organism. Extending the theoretical work of Edelman and others, the temporal organization of the brain is posited as functioning through "re-entry" and "temporal tagging" and binds the wide range of possible times to a unified cognitive experience which is held in unison with the outside world. Dysfunction in this system is reflected in the temporal discord seen in cases of aging, sleep disorder, jet-lag, and shift-work, as well as in mental disorders and drug-induced changes in consciousness. The extent to which neuroendocrine structures contribute to the neurocognitive mechanisms which underlie consciousness has so far not been explored. Therefore, neuroendocrine mechanisms contributing to the temporal organization of the brain are reviewed. It is concluded that time-and its neuroendocrine correlate melatonin-is a binding principle for organizing conscious experience.

Sleep Dysfunction in Alzheimer's Disease and Other Dementias

Changes in sleep architecture and circadian rhythms, including increased sleep latency and nighttime awakenings, decreased slow-wave sleep, rapid eye movement sleep, and total sleep time, and increased daytime napping are widespread in people with dementia. In addition, cyclic agitation episodes ("sundowning"), nightmares or hallucinations, sleep attacks, and nocturnal behavioral outbursts are associated with specific dementia syndromes. Sleep hygiene recommendations, particularly those aimed at reducing daytime sleep and improving the sleep environment and routine, can offset the circadian disturbances of some dementia patients. However, they can be burdensome for caregivers to implement, and must be targeted to the specific patterns of sleep disturbances patients are experiencing. Pharmacologic treatments may be useful for symptomatic treatment of insomnia and nighttime behavioral disturbances in dementia patients, but there have been few controlled trials demonstrating their efficacy or long-term safety. Clonazepam is highly effective for treating the nighttime behaviors associated with rapid eye movement behavior disorder. For most dementia patients, however, the side effect risks of prolonged use of sedating medications must be weighed against the potential benefits. Dementia patients should be evaluated for common primary sleep disorders that may contribute to nighttime behavioral disturbances and impact treatment decisions. Continuous positive airway pressure, the gold standard for treating obstructive sleep apnea, can be tolerated by mild to moderately demented individuals with support from supervising caregivers. Increased daily light exposure and physical activity may help normalize circadian rest-activity rhythms in some dementia patients, although the frequency and dose needed to maintain treatment effects is currently not known.

Case study of circadian rhythm sleep disorder following haloperidol treatment: reversal by risperidone and melatonin

A patient with Gilles de la Tourette syndrome treated with haloperidol, ingested once daily after awakening from sleep, exhibited an irregular sleep-wake pattern with a free-running component of approximately 48 h. Transfer to risperidone, ingested once daily after awakening from sleep, was beneficial resulting in a sleep-wake cycle more synchronized at the appropriate phase to the external zeitgebers, and fewer nocturnal disturbances. The circadian sleep-wake schedule was fully synchronized when the patient had been subsequently treated with melatonin at 21:00h, before intended nocturnal sleep, in addition to risperidone in the morning. Restoration of the sleep-wake circadian pattern was accompanied by the patient's subjective report of significant improvement in his quality of life, social interactions, and occupational status. This observation suggests that circadian rhythm sleep disorders can be related to the typical neuroleptic haloperidol and restored by the atypical neuroleptic risperidone. Similar findings reported in patients suffering from other disorders support the hypothesis that the described disruption of the sleep-wake schedule is medication rather than illness-related. Therefore, it is very important to realize that circadian rhythm sleep disorders may be a side effect of neuroleptics.

Circadian rhythm sleep disorders (CRSD)

Circadian Rhythm Sleep Disorders (CRSD) are a group of sleep disorders characterized by a malsynchronization between a person's biological clock and the environmental 24-h schedule. These disorders can lead to harmful psychological and functional difficulties and are often misdiagnosed and incorrectly treated due to the fact that doctors are unaware of their existence. In the following review we describe the characteristics of CRSD, diagnosis, treatment as well as their relationship to psychopathology, psychotropic drugs and head trauma.

Effects of clozapine on sleep measures and sleep-associated changes in growth hormone and cortisol in patients with schizophrenia

There have been limited reports on the effect of the atypical anti-psychotic agent clozapine on sleep measures and hormone secretion. The goal of this study was to determine the type, rate, and extent of changes in sleep measures and nighttime secretion of growth hormone (GH) and cortisol during clozapine treatment. Five schizophrenic patients (age: 32.4+/-7.4) and five age- and sex-matched normal subjects (age: 33.0+/-5.1) underwent nocturnal polysomnography (NPSG) before clozapine therapy (S1), and during early and late clozapine therapy (S2 and S3). Serum GH and cortisol levels were monitored during each NPSG. NPSG findings showed that the mean total sleep time, sleep efficiency, and duration of awakening were increased at S2, and maintained until S3. The mean amounts of stage 2 sleep at S2 and S3 increased significantly compared with that of S1. In unmedicated schizophrenic patients, the mean plasma GH level in rapid eye movement sleep was lower than during the waking stage, and the mean level of plasma cortisol was higher during the waking stage. Plasma cortisol levels did not differ between control subjects and patients at any time, but clozapine treatment decreased plasma cortisol levels at S2 compared with S1 and S3. Plasma GH levels were unchanged by clozapine treatment. Clozapine improved sleep continuity and increased stage 2 sleep time from the beginning of therapy. These effects were maintained through at least 7 weeks of therapy. However, clozapine did not affect the relationship of plasma GH and cortisol levels with sleep stages in schizophrenic patients.

Circadian rhythm sleep disorders as a possible side effect of fluvoxamine

Sleep problems, day somnolence, and fatigue as a result of psychotropic drugs are very common. Psychiatrists usually consider these effects a result of insomnia and treat them by prescribing sleeping pills or other benzodiazepine agents. We describe here 10 cases of circadian rhythm sleep disorders (CRSD)--and not merely insomnia--as a possible side effect of fluvoxamine (FVA). Two other serotonin reuptake inhibitors, fluoxetine and clomipramine, did not induce CRSD in any of these 10 patients. We speculate that FVA-induced CRSD is caused by the effect of FVA on serotonin and melatonin levels in the central nervous system. CRSD as a side effect of FVA can be treated by replacing the suspected FVA or adding melatonin to a beneficial FVA treatment. Thus, it is important to be aware of possible iatrogenic CRSD in order to treat appropriately. Prospective studies are needed to confirm our observation and to study the influence of other psychotropic drugs on sleep-wake schedule.