Multivariate study of sleep EEG in depression

The effects of antidepressant treatment on sleep disturbances in depression

Sleep problems are classical complaints in depressed patients. Polygraphie recordings performed in drug free depressed patients during an acute episode of the illness have allowed description of sleep continuity, architecture and REM sleep disturbances. While the specificity of these abnormalities is not fully established, these perturbations appear to be core symptoms of the depressive episode. Antidepressants drugs, whatever their pharmacological profile have been shown to suppress or at least to reduce REM sleep. However, the effects of these drugs on sleep continuity and architecture seem to be related to their specific pharmacological action.

Alterations of neural network organisation during rapid eye movement sleep and slow-wave sleep in major depression: Implications for diagnosis, classification, and treatment

The aim of this study was to empirically investigate the network organisation during rapid eye movement sleep (REMS) and slow-wave sleep (SWS) using the effective connectivity measured using the Granger causality to identify new potential biomarkers for the diagnosis, classification, and potential favourable response to treatment in major depression. Polysomnographic data were analysed from 24 healthy individuals and 16 major depressed individuals recruited prospectively. To obtain the 19×19 connectivity matrix of all possible pairwise combinations of electrodes by the Granger causality method from our electroencephalographic data, we used the Toolbox MVGC multivariate Granger causality. The computation of network measures was realised by importing these connectivity matrices into the EEGNET Toolbox. Major depressed individuals (versus healthy individuals) and those with endogenous depression (versus those with neurotic depression) present alterations of small-world network organisation during REMS, whereas major depressed individuals with potential favourable response to electroconvulsive therapy (versus those with potential unfavourable response) have a less efficient small-world network organisation during SWS. Thus, alterations in network organisation during REMS could be biomarkers for the diagnosis and classification of major depressive episodes, whereas alterations of network organisation during SWS could be a biomarker to predict potential favourable response to treatment by electroconvulsive therapy.

Sleep-wake cycle in young and older persons with a lifetime history of mood disorders

Considering the marked changes in sleep and circadian rhythms across the lifespan, age may contribute to the heterogeneity in sleep-wake profiles linked to mood disorders. This study aimed to investigate the contributions of age and depression severity to sleep-wake disturbances. The Hamilton Depression Rating Scale (HDRS) was administered to assess current symptoms severity in 238 persons with a history of a mood disorder between 12 and 90 years of age (y.o.). Actigraphy was recorded over five to 22 days. Regression analyses and analyses of variance [age (12–19 y.o., 20–39 y.o., 40–59 y.o., and ≥60 y.o.) by depression severity (HDRS< and ≥8)] were conducted. The 12–19 y.o. and 20–39 y.o. groups had a delayed sleep schedule and acrophase compared to all other groups. The ≥60 y.o. group had a lower rhythmicity and amplitude (p≤.006) than the 12–19 y.o. group (p≤.046). Participants with a HDRS≥8 spent longer time in bed, had later sleep offset times and had lower circadian rhythmicity than those with a HDRS<8 (p≤.036). Younger age and higher HDRS score correlated with later sleep onset and offset times, longer time in bed, higher WASO, lower sleep efficiency and later acrophase (p≤.023). Age was a significant predictor of delayed sleep and activity schedules (p≤.001). The profile of sleep-wake cycle disturbances associated with mood disorders changes with age, with prominent sleep phase delay during youth and reduced circadian strength in older persons. Conversely, disruptions in sleep consolidation seem more stable across age.

Sleep Disturbances in Pediatric Depression

Depressive illness beginning early in life can have serious developmental and functional consequences. Therefore, understanding its etiology and pathophysiology during this developmental stage is critical for developing effective prevention and intervention strategies. There is considerable evidence of sleep alterations in adult major depressive disorder. However, studies in children and adolescents have not found consistent changes in sleep architecture paralleling adult depression. This review article summarizes sleep polysomnography research in early-onset depression, highlighting the factors associated with variable findings across studies. In addition, potential avenues for future research will be suggested in order to develop more comprehensive theoretical models and interventions for pediatric depression.

A meta-analysis of electroencephalographic sleep in depression: evidence for genetic biomarkers

BACKGROUND

Research on whether any electroencephalographic (EEG) sleep abnormalities observed among individuals with major depressive disorder (MDD) represent genetic biomarkers remains inconclusive. We aimed to identify EEG-based biomarkers of MDD through a review of studies from three populations: individuals with MDD, individuals with MDD under remission, and never depressed high-risk probands (HRPs) of individuals with MDD.

METHODS

We searched databases such as MEDLINE and PsycINFO for EEG studies published since 1970. Of the 886 records, our selection criteria identified 56 studies that employed standardized EEG scoring procedures and addressed confounds such as participant reactivity and drug effects. We then used fixed-effects models to calculate average weighted mean differences in EEG parameters between clinical groups across these studies.

RESULTS

Individuals with MDD differed significantly from control subjects on several EEG variables. However, remitted individuals showed normalization of all affected EEG parameters except rapid eye movement (REM) density and slow-wave sleep (SWS). Surprisingly, proportion of SWS was significantly shorter during remission than depression. Never-depressed HRPs also exhibited significantly elevated REM density and reduced SWS. Finally, these parameters constituted the only two EEG variables that were not moderated by depression severity.

CONCLUSIONS

Individuals experiencing MDD and those in remission exhibit increased REM density and shortened SWS, as do HRPs with no history of MDD. Thus, this combination of EEG features may represent a genetic biomarker of MDD. Further, SWS appears to be shorter during remission than depression, suggesting its role as both a genetic marker as well as a biological scar of the disorder.

Smoking and sleep disorders

Cigarette smoking is the most important cause of preventable disease, disability, and premature death in the United States. In addition to adverse effects on respiratory, cardiovascular, cerebrovascular, and other systems, accumulating evidence indicates that cigarette smoking may also increase morbidity by adversely affecting sleep. This article focuses on the effects of cigarette smoking, nicotine, and pharmacologic agents used for smoking cessation on neuronal systems regulating sleep and clinically apparent sleep disorders.

Sleep-wake mechanisms and drug discovery: sleep EEG as a tool for the development of CNS-acting drugs

Sleep laboratory investigations constitute a unique noninvasive tool to analyze brain functioning, Polysomnographic recordings, even in the very early phase of development in humans, are mandatory in a developmental plan of a new sleep-acting compound. Sleep is also an interesting tool for the development of other drugs acting on the central nervous system (CNS), Indeed, changes in sleep electroencephalographic (EEG) characteristics are a very sensitive indication of the objective central effects of psychoactive drugs, and these changes are specific to the way the drug acts on the brain neurotransmitter systems. Moreover, new compounds can be compared with reference drugs in terms of the sleep EEG profile they induce. For instance, cognitive enhancers involving cholinergic mechanism have been consistently demonstrated to increase rapid eye movement (REM) sleep pressure, and studying drug-induced slow wave sleep (SWS) alteration is a particularly useful tool for the development of CNS compounds acting at the 5-HT(2A/C) receptor, such as most atypical antipsychotics and some antidepressant drugs. The sleep EEG profile of antidepressants, and particularly their effects on REM sleep, are specific to their ability to enhance noradrenergic or serotonergic transmission, it is suggested that the effects of noradrenergic versus serotonergic reuptake inhibition could be disentangled using specific monoamine depletion tests and by studying drug effects on sleep microsiructure.

Sleep and depression--results from psychobiological studies: an overview

Disturbances of sleep are typical for most depressed patients and belong to the core symptoms of the disorder. Polysomnographic sleep research has demonstrated that besides disturbances of sleep continuity, in depression sleep is characterized by a reduction of slow wave sleep and a disinhibition of REM sleep, with a shortening of REM latency, a prolongation of the first REM period and increased REM density. These findings have stimulated many sleep studies in depressive patients and patients with other psychiatric disorders. In the meantime, several theoretical models, originating from basic research, have been developed to explain sleep abnormalities of depression, like the two-process-model of sleep and sleep regulation, the GRF/CRF imbalance model and the reciprocal interaction model of non-REM and REM sleep regulation. Interestingly, most of the effective antidepressant agents suppress REM sleep. Furthermore, manipulations of the sleep-wake cycle, like sleep deprivation or a phase advance of the sleep period, alleviate depressive symptoms. These data indicate a strong bi-directional relationship between sleep, sleep alterations and depression.

Morning and evening TSH response to TRH and sleep EEG disturbances in major depressive disorder

1. The aim of this study was to investigate hypothalamo-pituitary-thyroid axis (HPTA) functioning and sleep EEG disturbances in major depressive disorder. 2. Thyroid function was evaluated by determination of TSH levels before and after 8 AM and 11 PM TRH administration on the same day in a sample of 113 consecutively-admitted DSM-IV major depressed inpatients (72 females aged 44.3 +/- 13.0 and 41 males aged 45.7 +/- 10.7) that underwent sleep EEG recordings. 3. A blunted TSH response occurred in 15.9% for 8 AM deltaTSH (maximum increment above baseline at the 8 AM TRH challenge), in 39.8% for 11 PM deltaTSH and in 77% for deltadeltaTSH (difference between 11 PM deltaTSH and 8 AM deltaTSH). A negative correlation between deltadeltaTSH and duration of awakenings after sleep onset, and a shorter sleep onset latency in patients with a blunted 11 PM deltaTSH were found, but these two significant relationships disappeared after controlling for the effects of gender and age. 4. The present findings do not support the hypothesis that, in major depression, HPTA dysfunctioning, as reflected in TSH response to TRH, may be related to sleep EEG disturbances.

Shortened REM latency as a psychobiological marker for psychotic depression? An age-, gender-, and polarity-controlled study

BACKGROUND

Previous reports suggest that the clinical dichotomy separating psychotic and nonpsychotic depression corresponds to different neurobiological profiles. The aim of the present study is to further investigate the psychobiological correlates of these two particular depressive subtypes.

METHODS

Thyroid-stimulating hormone response to thyrotropin-releasing hormone postdexamethasone cortisol levels, and electroencephalgraphic sleep characteristics of 44 psychotic major depressive patients were compared to those of 44 nonpsychotic depressives matched for age, gender, and polarity.

RESULTS

Some biological disturbances usually associated with depression (increased wakefulness, diminished rapid eye movement latency, hypercortisolism, blunted thyroid-stimulating hormone response to thyrotropin-releasing hormone stimulation) seemed to be significantly more pronounced in the psychotic depressed group as a reflection of greater illness severity; however, shortened REM latency was not influenced by severity and seemed to be more specifically related to the co-occurrence of psychotic and depressive symptoms.

CONCLUSIONS

Our data provide further support for the validity of the clinical dichotomy separating psychotic and nonpsychotic major depression independently of severity.

Does sleep EEG data distinguish between UP, BPI or BPII major depressions? An age and gender controlled study

Clinical characteristics and sleep EEG data of 14 unipolar (UPR), 14 bipolar I (BPI) and 14 bipolar II (BPII) patients, matched for age and gender, were investigated during a major depressive episode. We observed a remarkable similarity in the clinical characteristics of the three samples and, concerning sleep EEG data, a trend to a higher percentage of awakening among BPI patients. Pairwise comparisons of the three subgroups showed that only the Newcastle rating scale score reached significant difference between BPI and UPR groups. We observed trends regarding the difference of awakening both between BPI and BPII groups and between BPI and UPR groups, difference of percentage of REM sleep between BPI and BPII groups and difference of Sleep Period Time between BPII and UPR groups. We also observed that the distribution of REM latencies in the BPI subgroup was different from the two others.

Neuroendocrine and clinical characteristics of major depressed patients exhibiting sleep-onset REM

BACKGROUND

Previous reports suggest an association between sleep-onset REM (SOREM) and some clinical characteristics in depressive illness such as age, psychosis, and depression severity. The present study is aimed at further investigating clinical and neuroendocrine correlates of SOREM, controlling for the age-related variability in clinical data.

METHODS

Thyroid-stimulating hormone response to thyrotropin-releasing hormone, postdexamethasone cortisol levels, and clinical characteristics of 25 major depressive (MD) patients exhibiting SOREM in at least one of three consecutive recording nights were compared to those of 25 age- and sex-matched MD patients with three REM latencies above 50 min.

RESULTS

SOREM patients experienced more affective episodes leading to hospitalization and a shorter duration of current episode than patients with three REM latencies above 50 min. No association between psychosis and SOREM could be demonstrated, and hypothalamic-pituitary-adrenal or -thyroid axis disturbances were not more prevalent in SOREM patients.

CONCLUSIONS

Our results suggest that clinical history rather than cross-sectional clinical characteristics relates to the occurrence of SOREM in major depressed patients.

The dexamethasone suppression test and sleep electroencephalogram in nonbipolar major depressed inpatients: a multivariate analysis

BACKGROUND

The present study further examined relationships between postdexamethasone cortisol plasma values and sleep electroencephalogram (EEG) parameters.

METHODS

The dexamethasone suppression test (DST) and polysomnographic recordings were performed in a sample of 300 inpatients with primary major depressive disorder (MDD) (102 men and 198 women, mean age 44 +/- 12 years, range 20-74 years) consecutively admitted to Erasme Hospital (Brussels, Belgium) between 1981 and 1992.

RESULTS

The DST was abnormal in 40% of the sample. Postdexamethasone cortisol plasma values at 4:00 PM were significantly influenced by age, but not by gender. They were also significantly and positively correlated with weight loss, total scores on the Hamilton Depression Rating Scale, total scores on the Newcastle Scale, percentage of awakenings during sleep, and percent of stage 1. They were significantly and negatively correlated with percent of stage 2, slow-wave sleep, and REM sleep. Multiple regression analyses were conducted in two successive steps. First among clinical variables, only age and depressive symptom severity remained correlated with postdexamethasone plasma cortisol values. In the second step, with age and severity held constant, postdexamethasone plasma cortisol values were positively associated with amount of wake time and stage 1, and negatively with amount of slow-wave sleep.

CONCLUSIONS

These findings provide further indirect support for an overarousal state in MDD with sympathoadrenal system hyperactivity and impaired sleep continuity. They also underline the importance of taking into account various clinical confounding factors in the interpretation of both DST and sleep EEG results.

Sleep-onset rapid eye movement periods in neuropsychiatric disorders: implications for the pathophysiology of psychosis

This paper reviews the literature describing the occurrence of sleep-onset rapid eye movement periods in narcolepsy, schizophrenia, psychotic depression, and delirium tremens; the association of narcolepsy with psychotic disorders; the neuropathology of the brainstem in narcolepsy and schizophrenia; and other behavioral disorders resulting from probable brainstem pathology. These findings suggest that some forms of psychosis are a manifestation of pathophysiological changes in the brainstem. Some implications of this hypothesis for the treatment of psychoses are discussed. Future research should investigate psychoses and the psychobiological correlates of such biological markers as sleep-onset rapid eye movement periods across diagnostic categories.

Comparative studies of the biological distinction between unipolar and bipolar depressions

Although unipolar depression and bipolar depression are considered distinct entities both by clinicians and researchers, it is not clear whether a pathophysiological distinction, which is the bridge between etiology and treatment, exists between these two conditions. The objective of this paper was to systematically review the studies that examined the biological differences between unipolar and bipolar depression. Using computerized Medline and manual searches, we located and reviewed studies that directly compared patients with unipolar depression with bipolar depressed patients on at least one biological variable. The results showed that patients with bipolar depression had lower levels of urinary NE and its metabolites and lower platelet MAO activity, and higher platelet free and stimulated intracellular calcium levels compared with unipolar depressed patients, but none of the variables examined appeared to differentiate the two groups consistently. We discuss some of the methodological flaws that might have contributed to this, and suggest that further studies should control for such confounding variables.

Critical analysis of the theories advanced to explain short REM sleep latencies and other sleep anomalies in several psychiatric conditions

One of the most consistent and most studied sleep modifications in several psychiatric conditions is the shortening of the rapid eye movement (REM) sleep latency. While its clinical usefulness is still to be proven and its meaning relatively obscure, the appearance of a short REM latency continues to be a daily fact in sleep laboratories. Many theories compete to explain what is observed, the most important being the circadian rhythm hypotheses, the homeostatic model and the reciprocal interaction model. These three are summarised and their pros and cons are exposed in a systematic manner. Points of conflict, possible convergences and limitations are discussed in the light of recent developments on the general theories of sleep regulation.

Neuroendocrine and sleep variables in major depressed inpatients: role of severity

To evaluate the reliability of the endogenous concept of depressive illness according to the Newcastle Endogenous Depression Diagnostic Index (NEDDI), 155 major depressive inpatients with NEDDI scores > or = 6 (endogenous) were matched for gender and age (+/- 5 years) to 155 major depressive inpatients with NEDDI scores < 6 (nonendogenous). When sleep polygraphic variables, neuroendocrine parameters (dexamethasone suppression and thyrotropin-releasing hormone tests), and various clinical variables (unipolar/bipolar status, psychotic/nonpsychotic subtype, and severity of the depressive episode) were examined, statistically significant differences between endogenous and nonendogenous patients emerged for three variables: the thyroid-stimulating hormone response to the thyrotropin-releasing hormone test, the dexamethasone suppression test response at 16:00 h, and the percentage of time awake during the night. However, when the effects of age and severity of depression were controlled, those differences disappeared.

Relationship between the Newcastle scale and sleep polysomnographic variables in major depression: a controlled study

In order to investigate the reliability of the endogenous concept of depressive illness with some sleep EEG parameters, we studied 39 male inpatients suffering from a nonbipolar major depressive episode (15 endogenous (MDDE) and 24 nonendogenous (MDDNE)) and 20 age and sex matched normal controls (C). All patients were diagnosed according to the Research Diagnostic Criteria (RDC) and the endogenous character of the episode was assessed with the Newcastle Endogenous Depression Diagnostic Index. We found significant differences for the following variables between the three groups (MDDE, MDDNE and C): sleep period time (SPT), REM latency, stage II, slow wave sleep (SWS), REM latency expressed as a continuous variable and REM latency expressed as a dichotomizing variable with a threshold of 50 min. These variables were used to compare the endogenous and the nonendogenous depressed patients and also the major depressed patients and the normal controls. Significant differences were observed between all depressed patients and control subjects for amount of SWS and REM latency which were both reduced in endogenous and nonendogenous depressed patients. No significant difference was observed between endogenous and nonendogenous depressed patients, except for the REM latency expressed with a threshold of 50 min (more frequently observed in endogenous depressed patients). Our data support the observation that SWS and REM latency are decreased in major depressive patients. However, in this age and sex controlled study, subtyping nonbipolar major depressive disorder for an endogenous character by the Newcastle Endogenous Depression Diagnostic Index (NEDDI) did not reveal further significant differences for sleep EEG variables, except for the shortening of the REM latency expressed as a dichotomizing variable.

TSH response to TRH and EEG sleep in non-bipolar major depression: a multivariate approach

The TSH response to TRH and selected sleep EEG variables were studied in a homogeneous sample of 280 non-bipolar major depressed inpatients (95 males and 185 females). The TSH response to TRH was blunted in 28% of the sample. delta max TSH was correlated negatively with age, Hamilton rating scale, Newcastle scale, percentage of wake, and positively with basal TSH, percentage of stage II, slow wave sleep, REM sleep and REM latency. delta max TSH was also lower in male patients and in patients suffering from an endogenous or a psychotic subtype of major depression. Basal TSH was only correlated negatively with the Newcastle score. In view of intercorrelations between all these variables, and because of the confounding effect of age, gender and severity on both the TSH response to TRH and sleep EEG variables, a multiple regression analysis was performed and demonstrated that basal TSH and gender were the two variables with the highest contribution to the delta max TSH variance, followed by age and the presence of psychotic symptoms. When controlling strictly for these significant effects, correlation with the severity or with the endogenous character of depression, and with sleep EEG parameters disappeared.

Sleep in depression: the influence of age, gender and diagnostic subtype on baseline sleep and the cholinergic REM induction test with RS 86

One hundred and eight healthy controls and 178 patients with a major depressive disorder according to DSM-III were investigated in the sleep laboratory after a 7-day drug wash-out period. Subsamples of 36 healthy controls and 56 patients additionally took part in the cholinergic rapid eye movement (REM) sleep induction test with RS 86. Data analysis revealed that age exerted powerful influences on sleep in control subjects and depressed patients. Sleep efficiency and amount of slow wave sleep (SWS) decreased with age, whereas the number of awakenings, early morning awakening, and amounts of wake time and stage 1 increased with age. REM latency was negatively correlated with age only in the group of patients with a major depression. Statistical analysis revealed group differences for almost all parameters of sleep continuity with disturbed indices in the depressed group. Differences in SWS were not detected. REM latency and REM density were altered in depression compared to healthy subjects. Sex differences existed for the amounts of stage 1 and SWS. The cholinergic REM induction test resulted in a significantly more pronounced induction of REM sleep in depressed patients compared with healthy controls, provoking sleep onset REM periods as well in those depressed patients showing baseline REM latencies in the normal range. Depressed patients with or without melancholia (according to DSM-III) did not differ from each other, either concerning baseline sleep or with respect to the results of the cholinergic REM induction test. The results stress the importance of age when comparing sleep patterns of healthy controls with those of depressed patients. Furthermore they underline the usefulness of the cholinergic REM induction test for differentiating depressed patients from healthy controls and support the reciprocal interaction model of nonREM-REM regulation and the cholinergic-aminergic imbalance hypothesis of affective disorders.

Symposium: Normal and abnormal REM sleep regulation: REM sleep in depression-an overview

Abnormalities of REM sleep, i.e. shortening of REM latency, lengthening of the duration of the first REM period and heightening of REM density, which are frequently observed in patients with a major depressive disorder (MDD), have attracted considerable interest. Initial hopes that these aberrant patterns of sleep constitute specific markers for the primary/endogenous sub-type of depression have not been fulfilled. The specificity of REM sleep disinhibition for depression in comparison with other psychopathological groups is challenged as well. Demographic variables like age and sex exert strong influences on sleep physiology and must be controlled when searching for specific markers of depressed sleep. It is still an open question whether abnormalities of sleep are state- or trait-markers of depression. Beyond baseline studies, the cholinergic REM induction test (CRIT) indicated a heightened responsitivity of the REM sleep system to cholinergic challenge in depression compared with healthy controls and other psychopathological groups, with the exception of schizophrenia. A special role for REM sleep in depression is supported by the well-known REM sleep suppressing effect of most antidepressants. The antidepressant effect of selective REM deprivation by awakenings stresses the importance of mechanisms involved in REM sleep regulation for the understanding of the pathophysiology of depressive disorders. The positive effect of total sleep deprivation on depressive mood which can be reversed by daytime naps, furthermore emphasizes relationships between sleep and depression. Experimental evidence as described above instigated several theories like the REM deprivation hypothesis, the 2-process model and the reciprocal interaction model of nonREM-REM sleep regulation to explain the deviant sleep pattern of depression. The different models will be discussed with reference to empirical data gathered in the field.

All-night electroencephalographic sleep and cranial computed tomography in depression. A study of unipolar and bipolar patients

All-night electroencephalographic (EEG) sleep recording and cranial computed tomography were performed in 24 inpatients with major depression (14 unipolar, 10 bipolar). The patients showed the characteristic "depression-like" EEG sleep alterations and their ventricular brain ratio (VBR) was increased compared with the control subjects. No major differences were found between the unipolar and the bipolar groups. There was a close and positive association between the VBR values and several measures of slow wave sleep. It is hypothesized that this relationship is due to an altered function of the limbic-hypothalamic-pituitary-adrenocortical axis in depression that affects both EEG sleep and brain morphology.

Sleep electroencephalography in depressive illness. A collaborative study by the World Health Organization

Eight WHO research centres from Europe, North America and Asia took part in a WHO study aimed at assessing the reliability and consistency of sleep-EEG abnormalities in major depression. Each centre was asked to include in the study ten depressed patients aged 20-65 years meeting the Research Diagnostic Criteria for a major depressive disorder, and to match them by age and gender with ten controls. There were 67 patients and 66 controls included in the study. Compared with controls, depressed patients showed sleep-continuity disturbances such as increase in sleep-onset latency, and decrease in total sleep time and in sleep efficiency. Stages 2 and 3, as percentages of total sleep time, were reduced in depressed patients, REM latency was shortened and REM density increased. These findings confirm the presence of specific sleep-EEG abnormalities in major depression.