Slow wave sleep and computed tomographic measures of brain morphology in schizophrenia

Sleep, sleep spindles, and cognitive functions in drug-naive patients with first-episode psychosis

STUDY OBJECTIVES

Various lines of clinical findings have suggested abnormalities in macro- or microstructural parameters of sleep in patients with schizophrenia. Meanwhile findings are inconclusive due to some confounding factors, such as the heterogeneity of the disorder, drug regimen, and duration of the illness. There are a few studies in the literature that have been conducted on drug-free patients with first-episode psychosis (FEP). Based on this knowledge, we aimed to explore sleep characteristics, sleep spindles, and neuropsychological profiles of the drug-naive patients with FEP.

METHODS

The study sample consisted of 21 drug-naive patients with FEP and 21 healthy participants. Polysomnography recordings were conducted for 2 subsequent nights. A neuropsychological test battery was administered for assessing cognitive functions. The Positive and Negative Syndrome Scale was applied to measure symptom severity of the patients. Spindle detection was performed visually.

RESULTS

According to the results of the study, the patient group's percentage of stage N2 sleep and sleep efficiency index was lower than in the control group. Among sleep spindle parameters, spindle density was found to be reduced in the patient group. The results of neuropsychological tests measuring executive functions, learning, and memory support the idea that there is a global cognitive deterioration from the early course of the disorder. In the psychotic group, negative symptoms were negatively correlated with verbal memory, learning, verbal fluency, and semantic organization. We found that the percentage of stage N3 sleep decreased while negative symptom severity increased. In addition, the percentage of stage N1 sleep increased as negative symptom severity increased. Reduction in stage N3 sleep was associated with an impairment in learning, verbal fluency, and response inhibition. The sleep spindle density and cognitive functions did not show any associations.

CONCLUSIONS

Taken together, these findings suggest that patients with FEP show global cognitive impairment (except for attention and processing speed), which is associated with changes in sleep architecture and higher score in a scale assessing negative symptoms. We conclude that cognitive function and spindle parameters differ nonlinearly among patients with FEP.

Troubles psychotiques et troubles du sommeil : revue de la littérature

Contexte La disparition de la nomenclature des troubles du sommeil dits primaires ou secondaires, rendue obsolète par le Manuel diagnostique et statistique des troubles mentaux (DSM-5), représente bien l’engouement académique actuel pour ce domaine de recherche. Il est de plus en plus reconnu que les troubles du sommeil sont plus que de simples conséquences d’un trouble psychiatrique et qu’ils peuvent persister malgré un traitement adéquat de la condition comorbide et même précéder ou exacerber cette dernière. Les troubles du sommeil dans les troubles psychotiques, très fréquents, sont donc devenus un sujet d’actualité, représentant une cible d’intervention jusqu’ici sous-estimée.

Objectif Cet article vise à présenter l’état des connaissances actuelles sur la relation entre les troubles du sommeil et les troubles psychotiques ainsi que sur l’utilisation de la thérapie cognitivo-comportementale (TCC) pour traiter les troubles du sommeil dans ce contexte.

Méthode L’article fait une recension narrative de la littérature pour décrire la relation bidirectionnelle entre la psychose et les troubles du sommeil, les corrélations cliniques et les traitements ciblant l’insomnie chez les patients psychotiques.

Résultats Malgré la présence d’une relation entre les troubles du sommeil et les troubles psychotiques, les mécanismes neuronaux, hormonaux et socioculturels régissant cette relation demeurent encore incertains. Bien que l’association reliant les troubles du sommeil et les troubles psychotiques demeure à clarifier, les études démontrent qu’elle serait bidirectionnelle et peut engendrer un cercle vicieux où ces deux composantes s’aggravent mutuellement. Dans ce contexte de comorbidités, les modèles unifiés en TCC deviennent un traitement de choix, à condition d’adapter les protocoles de TCC pour insomnie (TCC-i) à une population avec trouble psychotique (TCC-ip).

Conclusion Malgré la complexité de la relation entre les troubles psychotiques et ceux du sommeil, la TCC-i a été démontrée efficace pour traiter les troubles du sommeil dans une population psychotique et pourrait, dans certains cas, permettre d’alléger la symptomatologie psychotique. De futures études sur ce domaine pourraient permettre le développement de protocoles de thérapie cognitivo-comportementale pour les troubles du sommeil mieux adaptés à la population avec troubles psychotiques.

Effect of Olanzapine on Clinical and Polysomnography Profiles in Patients with Schizophrenia

Acute and short-term administration of olanzapine has a favorable effect on sleep in schizophrenia patients. This study aimed to clarify the effect of olanzapine on polysomnographic profiles of schizophrenia patients during the acute phase of illness after controlling for previous drug exposure. Twenty-five drug-naïve or drug-free schizophrenia patients were assessed at baseline and after six weeks of olanzapine treatment on Brief Psychiatric Rating Scale (BPRS), Positive and Negative Syndrome Scale (PANSS), and Udvalg for Kliniske Undersogelser (UKU) side-effect rating scale and a whole-night polysomnography; fifteen patients completed the study. There was a significant reduction in all psychopathological variables with maximum reduction in PANSS total, BPRS total, and PANSS positive scores. A significant increase in total sleep time (TST), sleep efficiency (SE), nonrapid eye movement (NREM) stage 1 duration, stage 3 duration, stage 4 duration, and stage 4 percentage of TST, number of rapid eye movement (REM) periods, REM duration, and REM percentage of TST was observed. REM latency at baseline inversely predicted the reduction in BPRS total and PANSS total and positive scores. In summary, short-term treatment with olanzapine produced significant improvement in clinical and polysomnography profiles of patients with schizophrenia with shorter REM latency predicting a good clinical response.

Reduced sleep spindle activity point to a TRN-MD thalamus-PFC circuit dysfunction in schizophrenia

Sleep disturbances have been reliably reported in patients with schizophrenia, thus suggesting that abnormal sleep may represent a core feature of this disorder. Traditional electroencephalographic studies investigating sleep architecture have found reduced deep non-rapid eye movement (NREM) sleep, or slow wave sleep (SWS), and increased REM density. However, these findings have been inconsistently observed, and have not survived meta-analysis. By contrast, several recent EEG studies exploring brain activity during sleep have established marked deficits in sleep spindles in schizophrenia, including first-episode and early-onset patients, compared to both healthy and psychiatric comparison subjects. Spindles are waxing and waning, 12-16Hz NREM sleep oscillations that are generated within the thalamus by the thalamic reticular nucleus (TRN), and are then synchronized and sustained in the cortex. While the functional role of sleep spindles still needs to be fully established, increasing evidence has shown that sleep spindles are implicated in learning and memory, including sleep dependent memory consolidation, and spindle parameters have been associated to general cognitive ability and IQ. In this article we will review the EEG studies demonstrating sleep spindle deficits in patients with schizophrenia, and show that spindle deficits can predict their reduced cognitive performance. We will then present data indicating that spindle impairments point to a TRN-MD thalamus-prefrontal cortex circuit deficit, and discuss about the possible molecular mechanisms underlying thalamo-cortical sleep spindle abnormalities in schizophrenia.

Sleep and mental disorders: A meta-analysis of polysomnographic research

Investigating sleep in mental disorders has the potential to reveal both disorder-specific and transdiagnostic psychophysiological mechanisms. This meta-analysis aimed at determining the polysomnographic (PSG) characteristics of several mental disorders. Relevant studies were searched through standard strategies. Controlled PSG studies evaluating sleep in affective, anxiety, eating, pervasive developmental, borderline and antisocial personality disorders, attention-deficit-hyperactivity disorder (ADHD), and schizophrenia were included. PSG variables of sleep continuity, depth, and architecture, as well as rapid-eye movement (REM) sleep were considered. Calculations were performed with the "Comprehensive Meta-Analysis" and "R" software. Using random effects modeling, for each disorder and each variable, a separate meta-analysis was conducted if at least 3 studies were available for calculation of effect sizes as standardized means (Hedges' g). Sources of variability, that is, sex, age, and mental disorders comorbidity, were evaluated in subgroup analyses. Sleep alterations were evidenced in all disorders, with the exception of ADHD and seasonal affective disorders. Sleep continuity problems were observed in most mental disorders. Sleep depth and REM pressure alterations were associated with affective, anxiety, autism and schizophrenia disorders. Comorbidity was associated with enhanced REM sleep pressure and more inhibition of sleep depth. No sleep parameter was exclusively altered in 1 condition; however, no 2 conditions shared the same PSG profile. Sleep continuity disturbances imply a transdiagnostic imbalance in the arousal system likely representing a basic dimension of mental health. Sleep depth and REM variables might play a key role in psychiatric comorbidity processes. Constellations of sleep alterations may define distinct disorders better than alterations in 1 single variable. (PsycINFO Database Record

The sleep effects of lurasidone: a placebo-controlled cross-over study using a 4-h phase-advance model of transient insomnia

BACKGROUND

Lurasidone, an atypical antipsychotic, is a potent 5-HT7 antagonist and D2 , 5-HT2A antagonist, and 5-HT1A partial agonist. As such, lurasidone would be expected to modulate sleep and circadian function but there have been no human studies of the sleep effects of a 5-HT7 antagonist. The purpose of this study was to assess effects of lurasidone on sleep.

METHODS

This was a cross-over, polysomnographic study involving 54 healthy volunteers who underwent two treatment periods (order randomized) each consisting of two nights in the laboratory: Night 1-lights out at usual bedtime; Night 2-4-h advance of sleep phase and randomization to either lurasidone 40 mg or placebo. The next morning impairment testing was carried out.

RESULTS

Lurasidone significantly (p < 0.05) increased total sleep time by an average of 28.4 min versus placebo, decreased wake time after sleep onset and wake time after the final awakening, and increased sleep efficiency. No other effects were found.

CONCLUSIONS

Lurasidone had a sleep maintenance effect without effects on sleep onset, rapid eye movement, or slow-wave sleep. Lurasidone is likely to be beneficial to patients with disturbed sleep, particularly those with sleep maintenance problems. Copyright © 2016 John Wiley & Sons, Ltd.

Sleep Disturbances in Schizophrenia

Sleep disturbances are prevalent in patients with schizophrenia and play a critical role in the morbidity and mortality associated with the illness. Subjective and objective assessments of sleep in patients with schizophrenia have identified certain consistent findings. Findings related to the sleep structure abnormalities have shown correlations with important clinical aspects of the illness. Disruption of specific neurotransmitter systems and dysregulation of clock genes may play a role in the pathophysiology of schizophrenia-related sleep disturbances. Antipsychotic medications play an important role in the treatment of sleep disturbances in these patients and have an impact on their sleep structure.

Sleep Organisation in Depression and Schizophrenia: Index of Endogenous Periodicity of Sleep as a State Marker [Retracted]

Background: Sleep disorders are frequent symptoms described in psychiatric patients with major depression or schizophrenia. These patients also exhibit changes in the sleep architecture measured by polysomnography (PSG) during sleep. The aim of the present study was to identify potential biomarkers that would facilitate the diagnosis based on polysomnography (PSG) measurements.Subjects and Methods: 30 patients with schizophrenia, 30 patients with major depression and 30 healthy control subjects were investigated in the present study. The mean age in the group with schizophrenia was 36.73 (SD 6.43), in the group of patients with depression 40.77 (SD 7.66), in the healthy controls group 34.40 (SD 5.70). The gender distribution was as follows: 18 male, 12 female in the group with schizophrenia; in the group of patients with depression 11 male, 19 female; in the control group 16 male and 14 female. All subjects underwent polysomnography (PSG) for a minimum time of 8 hours according to the criteria of Rechtschaffen & Kales (1968). The following polysomnographic (PSG) parameters were analyzed: sleep latency (SL), total sleep time (TST), waking time after sleep onset (WTASO), number of awakenings (NAW), slow wave sleep (SWS), rapid eye movement sleep (REM), rapid eye movement sleep latency (REML), first REM period (REM 1), and first NREM period (NREM 1). We tested the potential of multiple sleep variables to predict diagnosis in different groups by using linear discriminate analysis (LDA).Results: There were significant differences in polysomnography (PSG) variables between healthy control subjects and psychiatric patients (total sleep time, sleep latency, number of awakenings, time of awakening after sleep onset, REM 1 latency, REM 1 and index of endogenous periodicity). Importantly, LDA was able to predict the correct diagnosis in 88% of all cases.Conclusions: The presented analysis showed commonalities and differences in polysomnography (PSG) changes in patients with major depressive disorder and in patients with schizophrenia. Our results underline the potential of polysomnography (PSG) measurements to facilitate diagnostic processes.

Structural brain correlates of human sleep oscillations

Sleep is strongly conserved within species, yet marked and perplexing inter-individual differences in sleep physiology are observed. Combining EEG sleep recordings and high-resolution structural brain imaging, here we demonstrate that the morphology of the human brain offers one explanatory factor of such inter-individual variability. Gray matter volume in interoceptive and exteroceptive cortices correlated with the expression of slower NREM sleep spindle frequencies, supporting their proposed role in sleep protection against conscious perception. Conversely, and consistent with an involvement in declarative memory processing, gray matter volume in bilateral hippocampus was associated with faster NREM sleep spindle frequencies. In contrast to spindles, gray matter volume in the homeostatic sleep-regulating center of the basal forebrain/hypothalamus, together with the medial prefrontal cortex, accounted for individual differences in NREM slow wave oscillations. Together, such findings indicate that the qualitative and quantitative expression of human sleep physiology is significantly related to anatomically specific differences in macroscopic brain structure.

Sleep disturbance in mental health problems and neurodegenerative disease

Sleep has been described as being of the brain, by the brain, and for the brain. This fundamental neurobiological behavior is controlled by homeostatic and circadian (24-hour) processes and is vital for normal brain function. This review will outline the normal sleep-wake cycle, the changes that occur during aging, and the specific patterns of sleep disturbance that occur in association with both mental health disorders and neurodegenerative disorders. The role of primary sleep disorders such as insomnia, obstructive sleep apnea, and REM sleep behavior disorder as potential causes or risk factors for particular mental health or neurodegenerative problems will also be discussed.

Study factors influencing ventricular enlargement in schizophrenia: a 20 year follow-up meta-analysis

A meta-analysis was performed on studies employing the ventricular-brain ratio to compare schizophrenic subjects to that of normal controls. This was a follow-up to a similar meta-analysis published in 1992 in which study-, in addition to clinical-, factors were found to contribute significantly to the reported difference between patients with schizophrenia and controls. Seventy-two (N=72) total studies were identified from the peer reviewed literature, 39 from the original meta-analysis, and 33 additional studies published since which met strict criteria for inclusion and analysis - thus representing ~30 years of schizophrenia ventricular enlargement research. Sample characteristics from schizophrenics and controls were coded for use as predictor variables against within sample VBR values as well as for between sample VBR differences. Additionally, a number of factors concerning how the studies were conducted and reported were also coded. Obtained data was subjected to unweighted univariate as well as multiple regression analyses. In particular, results indicated significant differences between schizophrenics and controls in ventricular size but also the influence of the diagnostic criteria used to define schizophrenia on the magnitude of the reported VBR. This suggests that differing factors of the diagnostic criteria may be sensitive to ventricular enlargement and might be worthy of further examination. Interestingly, we observed an inverse relationship between VBR difference and the number of co-authors on the study. This latter finding suggests that larger research groups report smaller VBR differences and may be more conservative or exacting in their research methodology. Analyses weighted by sample size provided identical conclusions. The effects of study factors such as these are helpful for understanding the variation in the size of the reported differences in VBR between patients and controls as well as for understanding the evolution of research on complex clinical syndromes employing neuroimaging morphometrics.

Slow wave sleep deficits as a trait marker in patients with schizophrenia

BACKGROUND

Among the sleep abnormalities found in schizophrenia, slow wave sleep deficits have been found to persist even after the resolution of active psychotic symptoms. Further, such abnormalities are observed in young healthy individuals at high risk of schizophrenia, which suggest that slow wave sleep deficits might be trait marker in schizophrenia.

METHODS

Sleep EEG was recorded in 20 right handed patients aged 18-45 years with ICD-10 DCR diagnosis of schizophrenia, 14 first degree relatives and 20 age and sex matched controls. Patients were rated on Positive and Negative Syndrome Scale (PANSS) and Brief Psychiatric Rating Scale (BPRS) for assessment of psychopathology.

RESULTS

There was significant difference between the three groups in total sleep period (p<.01), total sleep time (p<.01), stage shifts (p<.05), stage 1 percentage of total sleep time (p<.05), stage 2 duration (p<.05), stage 3 latency (p<.05), stage 4 duration (p<.01) and stage 4 percentage of total sleep time (p<.01). There was significant positive correlation of REM percentage of total sleep time with BPRS total score (r(s) = .488, p = .029) and PANSS positive score (r(s) = .583, p = .007), whereas significant negative correlation of REM latency was found with BPRS total score (r(s) = -.640, p = .002) and PANSS positive score (r(s) = -.657, p = .002) in the patients.

CONCLUSIONS

Slow wave sleep deficits are a possible trait marker in patients with schizophrenia, which needs replication in further studies.

Sleep in psychiatric disorders: where are we now?

Although the precise function of sleep is unknown, decades of research strongly implicate that sleep has a vital role in central nervous system (CNS) restoration, memory consolidation, and affect regulation. Slow-wave sleep (SWS) and rapid eye movement (REM) sleep have been of significant interest to psychiatrists; SWS because of its putative role in CNS energy recuperation and cognitive function, and REM sleep because of its suggested involvement in memory, mood regulation, and possible emotional adaptation. With the advent of the polysomnogram, researchers are now beginning to understand some of the consequences of disrupted sleep and sleep deprivation in psychiatric disorders. The same neurochemistry that controls the sleep-wake cycle has also been implicated in the pathophysiology of numerous psychiatric disorders. Thus it is no surprise that several psychiatric disorders have prominent sleep symptoms. This review will summarize normal sleep architecture, and then examine sleep abnormalities and comorbid sleep disorders seen in schizophrenia, as well as anxiety, cognitive, and substance abuse disorders.

Is schizoaffective disorder a distinct categorical diagnosis? A critical review of the literature

Considerable debate surrounds the inclusion of schizoaffective disorder in psychiatric nosology. Schizoaffective disorder may be a variant of schizophrenia in which mood symptoms are unusually prominent but not unusual in type. This condition may instead reflect a severe form of either major depressive or bipolar disorder in which episode-related psychotic symptoms fail to remit completely between mood episodes. Alternatively, schizoaffective disorder may reflect the co-occurrence of two relatively common psychiatric illnesses, schizophrenia and a mood disorder (major depressive or bipolar disorder). Each of these formulations of schizoaffective disorder presents nosological challenges because the signs and symptoms of this condition cross conventional categorical diagnostic boundaries between psychotic disorders and mood disorders. The study, evaluation, and treatment of persons presently diagnosed with schizoaffective may be more usefully informed by a dimensional approach. It is in this context that this article reviews and contrasts the categorical and dimensional approaches to its description, neurobiology, and treatment. Based on this review, an argument for the study and treatment of this condition using a dimensional approach is offered.

Sleep in schizophrenia: impairments, correlates, and treatment

In untreated schizophrenia, psychotic decompensation is associated with profound insomnia, one of the prodromal symptoms associated with psychotic relapse. First- and second-generation antipsychotic medication can ameliorate this insomnia, but side effects may include sedation or residual insomnia. Patients who are clinically stable and medicated may continue to experience disturbed sleep, including long sleep-onset latencies, poor sleep efficiency, slow wave sleep deficits, and short rapid eye movement latencies. Schizophrenia also can be associated with comorbid sleep disorders, which may be enhanced or induced by antipsychotic medication. Sleep disorders in schizophrenia should be treated vigorously because normalized sleep and its restorative processes may be essential for a positive clinical outcome.

Clinical significance of sleep EEG abnormalities in chronic schizophrenia

This study aimed to investigate the relationship between measures of clinical symptom severity and sleep EEG parameters in a relatively diagnostically homogeneous group of patients with schizophrenia. We obtained sleep EEG data in 15 drug-free inpatients who met DSM-IV-R criteria for schizophrenia, undifferentiated type, with 15 age- and sex-matched normal controls over two consecutive night polysomnographic recordings. Clinical symptoms were assessed by the Positive and Negative Symptom Scale (PANSS) and Hamilton Rating Scale for Depression. Characteristic features of sleep disturbance were seen in patients with schizophrenia: profound difficulties in sleep initiation and maintenance, poor sleep efficiency, a slow wave sleep (SWS) deficit, and an increased REM density. SWS was inversely correlated with cognitive symptoms. REM density was inversely correlated with positive, cognitive, and emotional discomfort symptoms as well as PANSS total score. Our data demonstrate that drug-free patients with chronic undifferentiated type schizophrenia suffer from profound disturbances in sleep continuity and sleep architecture. Both the SWS deficit and cognitive impairment found in schizophrenics in this study may relate to similar underlying structural brain abnormalities.

Phencyclidine-induced changes in rat cortical gene expression identified by microarray analysis: implications for schizophrenia

Acute phencyclidine induces schizophrenia-like symptoms in healthy humans and psychotic episodes in schizophrenics. Although phencyclidine is known as a N-methyl d-aspartate receptor antagonist (NMDA-R), the molecular events underlying the behavioral symptoms remain largely unknown. Statistical analysis of oligonucleotide microarray data was used to identify phencyclidine-induced alterations in rat cortical gene expression. Acute phencyclidine produced a statistically significant change in 477 genes in rat prefrontal cortex (PFC), a brain area associated with cognitive dysfunction in schizophrenics. Real-time quantitative PCR (RTQ-PCR) confirmed a subset of these changes ranging from -59% to 255% (smallest confirmation: -19%). Subsequent time-course and dose-response studies using RTQ-PCR confirmed and extended the original microarray results. At the molecular level, genes altered by phencyclidine are related to diverse biological processes including stress, inflammatory response, growth and development, neural plasticity and signal transduction. Further analysis, aimed at assessing the relevance of our results to schizophrenia, revealed dysregulation of genes related to: (i) thalamocortical projections, (ii) neurotransmission and neuromodulation, (iii) thyroid hormone activity, (iv) oligodendrocyte linage, (v) brain lipid metabolism, (vi) sleep architecture and (viii) the velocardiofacial syndrome.

Sleep in schizophrenia patients and the effects of antipsychotic drugs

Insomnia is a common feature in schizophrenia. However, it seldom is the predominant complaint. Nevertheless, severe insomnia is often seen during exacerbations of schizophrenia, and may actually precede the appearance of other symptoms of relapse. The sleep disturbances of either never-medicated or previously treated schizophrenia patients are characterized by a sleep-onset and maintenance insomnia. In addition, stage 4 sleep, slow wave sleep (stages 3 and 4), non-REM (NREM) sleep in minutes and REM latency are decreased. The atypical antipsychotics olanzapine, risperidone, and clozapine significantly increase total sleep time and stage 2 sleep. Moreover, olanzapine and risperidone enhance slow wave sleep. On the other hand, the typical antipsychotics haloperidol, thiothixene, and flupentixol significantly reduce stage 2 sleep latency and increase sleep efficiency. Future research should address: (1) the sleep patterns in subtypes of schizophrenia patients; (2) the role of neurotransmitters other than dopamine in the disruption of sleep in schizophrenia; (3) the functional alterations in CNS areas related to the pathophysiology of schizophrenia during NREM sleep and REM sleep (brain imaging studies); (4) the short-term, intermediate-term, and long-term effects of atypical antisychotics on sleep variables.

Alcohol, slow wave sleep, and the somatotropic axis

When alcohol is a large proportion of daily nutrient energy, the network of signals for energy homeostasis appears to adapt with abnormal patterns of sleep and growth hormone (GH) release along with gradual acquisition of an addictive physical dependency on alcohol. Early relapse during treatment of alcoholism is associated with a lower GH response to challenge, perhaps reflecting an altered balance of somatostatin (SS) to somatropin releasing hormone (GHRH) that also affects slow wave sleep (SWS) in dependent patients. Normal patterns of sleep have progressively shorter SWS episodes and longer rapid eye movement (REM) episodes during the overall sleep period, but the early sleep cycles of alcoholics have truncated or non-existent SWS episodes, and the longer REM episodes occur in early cycles. During SWS delta wave activity, the hypothalamus releases GHRH, which causes the pituitary to release GH. Alcohol-dependent patients have lower levels of SWS power and GH release than normal subjects, and efforts to understand the molecular basis for this maladaptation and its relation to continued alcohol dependence merit encouragement. More needs to be learned about the possibility of decreasing alcohol dependency by increasing SWS or enhancing GHRH action.

Slow-wave sleep and ventricular size: a comparative study in schizophrenia and major depression

BACKGROUND

A slow-wave sleep (SWS) deficit and a shortened rapid eye movement (REM) sleep latency are commonly described in schizophrenia and depression. In addition, a close association between ventricular system measurements and SWS are reported in both disorders; however, a comparative, combined polysomnographic and computed tomographic investigation is lacking.

METHODS

In the present post hoc study we analyzed the electroencephalographic sleep pattern and the ventricular brain ratio (VBR) of 14 drug-naive schizophrenic patients and of 14 depressed patients who were drug-free for a sufficient time period.

RESULTS

Whereas the depressives showed the often described SWS and REM sleep changes, these measurements were quite normal in the schizophrenics. The VBR values were similar in both patient groups and exceeded in 71% of the schizophrenics and in 50% of the depressives the cutoff point of a "normal" VBR value. A close association between SWS and VBR was found in the depressives but not in the schizophrenics.

CONCLUSIONS

The results of the present study of drug-naive schizophrenic patients and of depressed patients indicate only a minor overlap between the pathophysiological changes observed in both disorders. Therefore, the present investigation adds evidence for the assumption that schizophrenia and depression are etiopathogenetically distinct entities, rather than representing points on a continuum of liability.