Failure to differentiate bipolar disorder from schizophrenia on measures of neuropsychological function

Performance on the Wechsler Adult Intelligence Scale (WAIS) in Japanese patients with bipolar and major depressive disorders in euthymic and depressed states

AIM

This study aimed to examine the cognitive performance of patients with bipolar disorder (BD) stratified by illness phase compared to that of patients with major depressive disorder (MDD) and healthy controls.

METHODS

Participants were 139 patients with BD (55 euthymic and 84 depressed), 311 patients with MDD (88 euthymic and 223 depressed), and 386 healthy controls who underwent the Wechsler Adult Intelligence Scale-Revised or the Third Edition. They were non-elderly Japanese individuals with normal estimated premorbid intelligence quotient (IQ; >90), group-matched for age, sex, and premorbid IQ.

RESULTS

The depressed BD group showed significantly lower scores on verbal IQ, performance IQ, full-scale IQ, and three group indexes of perceptual organization, working memory, and processing speed when compared with healthy controls (all P < 0.001). All IQs and working memory index were also significantly lower than those of the depressed MDD group. The depressed MDD group scored significantly lower than controls in performance IQ (P < 0.001), full-scale IQ, and only in the index of processing speed (P < 0.001). The euthymic BD group scored significantly lower than controls in performance IQ (P = 0.004), whereas the euthymic MDD group scored significantly lower than controls only in processing speed (P = 0.030).

CONCLUSION

Patients with BD appear to have global and more intense cognitive impairments in depressed states compared with those with MDD whose impairments seem to be apparent only in processing speed in the Wechsler Adult Intelligence Scale. Attenuated impairments appear to exist in euthymic states of both patients.

The neurocognitive functioning in bipolar disorder: a systematic review of data

BACKGROUND

During the last decades, there have been many different opinions concerning the neurocognitive function in Bipolar disorder (BD). The aim of the current study was to perform a systematic review of the literature and to synthesize the data in a comprehensive picture of the neurocognitive dysfunction in BD.

METHODS

Papers were located with searches in PubMed/MEDLINE, through June 1st 2015. The review followed a modified version of the recommendations of the Preferred Items for Reporting of Systematic Reviews and Meta-Analyses statement.

RESULTS

The initial search returned 110,403 papers. After the deletion of duplicates, 11,771 papers remained for further evaluation. Eventually, 250 were included in the analysis.

CONCLUSION

The current review supports the presence of a neurocognitive deficit in BD, in almost all neurocognitive domains. This deficit is qualitative similar to that observed in schizophrenia but it is less severe. There are no differences between BD subtypes. Its origin is unclear. It seems it is an enduring component and represents a core primary characteristic of the illness, rather than being secondary to the mood state or medication. This core deficit is confounded (either increased or attenuated) by the disease phase, specific personal characteristics of the patients (age, gender, education, etc.), current symptomatology and its treatment (especially psychotic features) and long-term course and long-term exposure to medication, psychiatric and somatic comorbidity and alcohol and/or substance abuse.

Cognitive compromise in bipolar disorder with chronic cannabis use: cause or consequence?

This article briefly reviews the neuropsychological deficits associated with bipolar disorder and examines how substance abuse, in particular chronic cannabis use, may contribute to these. The focus of the article is cannabis, owing to its popularity in patients with bipolar disorder, although many studies focus on its use in conjunction with other substances. The findings are contextualized within bipolar disorder, examining functional outcome.

Impairment in functional capacity as an endophenotype candidate in severe mental illness

Impairment in everyday functioning (also referred to as "disability") is a central feature of schizophrenia (SZ) and bipolar disorder, as well as other neuropsychiatric conditions. There is a genetic contribution to both SZ and bipolar illness (BPI), and the primary putative determinant of impairments in everyday functioning across these 2 conditions, cognitive impairments, also show substantial heritability and in fact have been proposed to be endophenotypes for these disorders. In this article, we review data and make our case that impairments in functional capacity, the functional abilities that result in functional disability, may also be a heritable trait that is common across neuropsychiatric illnesses such BPI and SZ. While there has been little previous research on the heritability of these abilities, it is an area receiving substantial research attention. We consider advances in the measurement of cognitive functioning in SZ that may facilitate the discovery of genetic influences on functional capacity. Functional capacity measures are proximal to real-world impairments, measured with suitable psychometric precision to be used in heritability analyses, and appear to be minimally influenced by environmental factors that may cause disability such as environmental factors, symptoms, and disability compensation. Our conclusion is that these functional capacity measures have potential to be the target of genetic analyses and that these measures should be considered across neuropsychiatric conditions where impairments in everyday functioning are present.

Cognitive abilities and clinical variables in bipolar I depressed and euthymic patients and controls

BACKGROUND

While studies demonstrated that bipolar patients (BP) display cognitive deficits during mood episodes and remission, little is known about the clinical influences underlying these deficits. The aim of this study was to compare the performance of euthymic and depressed BPs and non-affective/psychotic disorder controls at several cognitive tasks, exploring which clinical variables influenced the performance of these subtests. It is hypothesized that the cognitive deficits in rank order are: depressed BPs > euthymic BPs > controls.

METHODS

Sixty-five bipolar-I outpatients and thirty-four controls were assessed by the Brazilian version of the Wechsler Adult Intelligence Scale, Third Edition (WAIS-III). BPs were divided into depressed and euthymics, and these two groups were then compared to non-affective/psychotic disorder controls.

RESULTS

For 12 of 14 subtest scores, comparisons yielded statistically significant (p < 0.05) between-group differences, including three subtests of attention and working memory (Digit Span and its two subtests) with both depressed and euthymic BPs, compared to controls, displaying significantly worse performance, and six subtests of visual and working memory with depressed (but not euthymic) BPs performing worse than controls. For all subtests, comparisons of depressed and euthymic patients' scores were non-significant. Performance on several subtests was negatively predicted by the severity of the disorder in both patient groups.

LIMITATIONS

The cross-sectional design of the study, as well as confounding effects of medications and co-morbidities.

CONCLUSIONS

The fact that the impairment of cognitive performance of both groups of patients is influenced by the severity of the illness is consistent with the literature.

Neuropsychological function and dysfunction in schizophrenia and psychotic affective disorders

BACKGROUND

Mounting evidence suggests that compromised neurocognitive function is a central feature of schizophrenia. There are, however, schizophrenia patients with a normal neuropsychological (NP) performance, but estimates of the proportion of NP normal patients vary considerably between studies. Neurocognitive dysfunction is also a characteristic of other psychotic disorders, yet there are inconsistencies in the literature regarding the similarity to impairments in schizophrenia. NP normality in psychotic affective disorders has not been systematically studied.

METHODS

Data came from the Suffolk County Mental Health Project, an epidemiological study of first-admission patients with psychotic disorders. Respondents with a diagnosis of schizophrenia (N = 94) or schizoaffective disorder (N = 15), bipolar disorder (N = 78), and major depressive disorder (N = 48) were administered a battery of NP tests assessing 8 cognitive domains 2 years after index admission. Patients' performance profile was compared, and their NP status was classified based on 3 previously published criteria that vary in their stringency.

RESULTS

The 4 diagnostic groups had comparable NP performance profile patterns. All groups demonstrated impairments in memory, executive functions, and attention and processing speed. However, schizophrenia patients were more impaired than the other groups on all cognitive domains. Results were not attenuated when IQ was controlled. Prevalence of NP normality ranged between 16% and 45% in schizophrenia, 20% and 33% in schizoaffective disorder, 42% and 64% in bipolar disorder, and 42% and 77% in depression, depending on the criterion employed.

CONCLUSIONS

Evidence suggests that differences in NP performance between schizophrenia and psychotic affective disorders are largely quantitative. NP impairment is also common in psychotic affective disorders. A significant minority of schizophrenia patients are NP normal.

Do cognitive deficits in juvenile bipolar disorder persist into adulthood?

This article reviews neuropsychological research in adults with bipolar disorder and compares the findings with emergent data on neuropsychological function in juvenile bipolar disorder. Despite a recent surge of interest in childhood onset bipolar disorder, there remains a scarcity of neuropsychological literature investigating this population. From the study of adult bipolar disorder a substantial body of literature points to the existence of trait deficits in verbal and executive function that are detectable even during euthymia. In the nascent literature on neuropsychology in early onset bipolar, there is growing evidence to suggest that some of the deficits apparent in adults are also discernible in adolescents. Precise knowledge about when, how, and why these deficits appear requires future research of prodromal changes in neurocognition in childhood and adolescent bipolar disorder.

The sensitivity and psychometric properties of a brief computer-based cognitive screening battery in a depression clinic

At present, there is poor accuracy in assessing cognitive and vegetative symptoms in depression using clinician or self-rated measures, suggesting the need for development of standardized tasks to assess these functions. The current study assessed the psychometric properties and diagnostic specificity of a brief neuropsychological screening battery designed to assess core signs of depression; psychomotor retardation, attention and executive functioning difficulties, and impaired emotion perception within an outpatient psychiatry setting. Three hundred eighty-four patients with mood disorders and 77 healthy volunteers participated. A large percentage of patients met diagnostic criteria for Major Depressive Disorder alone (49%) or with another comorbid psychiatric disorder (24%). A brief, 25-min battery of computer-based tests was administered to control participants and patients measuring the constructs of inhibitory control, attention, visual perception, and both executive and visual processing speed. The patient groups performed significantly worse than the control group regardless of diagnosis on visual perception and attention accuracy and processing speed factors. Surprisingly, the anxiety disorder group performed better than several other psychiatric disorder groups in inhibitory control accuracy. Developing valid and reliable measures of cognitive signs in mood disorders creates excellent opportunities for tracking cognitive status prior to initiation of treatment, and allows for reliable retest following treatment.

Cognitive functions in euthymic patients with bipolar disorder

BACKGROUND

Recent studies have focused on the nature of cognitive dysfunction in bipolar patients. The purpose of the current study was to investigate cognitive performance of individuals with bipolar disorder compared to healthy control subjects during a well-established euthymic period.

METHODS

The sample consisted of 27 bipolar euthymic patients and 21 control subjects. Verbal and visual memory performance, attention, executive functions and psychosocial functions were evaluated for each participant.

RESULTS

Bipolar patients showed significant attentional deficit and executive dysfunction and also poor performance on verbal and visual memory tasks compared to the controls. Illness duration and lifetime total episode number and previous episode with psychotic features was associated with worsened performance on attention, executive and memory tasks. Psychosocial functioning was not associated with cognitive deficit.

CONCLUSIONS

The present study showed persistent cognitive impairment on inhibitory control and selective attention as well as poor performance on verbal and visual memory tests in a group of bipolar euthymic patients. The impaired neuropsychological performance was associated with duration of illness, total number of episodes per lifetime, and previous episodes with psychotic features. Attentional dysfunction seemed to be a trait abnormality for the sample studied.

Context processing performance in bipolar disorder patients

OBJECTIVES

Context processing is the adaptive control of current behavior through the use of prior context information. It has been found to be impaired in schizophrenia. Some studies have indicated that, compared with patients with schizophrenia, those with bipolar disorder (BPD) display a similar but less severe neuropsychological pattern of impairment. However, this cognitive dimension has not yet been examined in BPD patients in the existing literature.

METHODS

An expectancy version of the AX continuous performance test (AX-CPT) was administered to 15 bipolar outpatients and 26 healthy controls. Patients with schizophrenia, in which context processing deficits are known to occur, were used as a reference group.

RESULTS

Bipolar patients showed a context processing deficit relative to healthy controls, although this was less severe and generalized than in schizophrenia patients.

CONCLUSIONS

These findings suggest there are milder impairments in context processing in BPD compared with schizophrenia. However, the severity of possible context processing deficits in BPD may have been underestimated in our sample of mostly euthymic outpatients.

Neuropsychological functioning in adolescent children of mothers with a history of bipolar or major depressive disorders

BACKGROUND

Growing evidence demonstrates an association of neuropsychological deficits with mood disorders, but it is not yet clear whether these deficits are risk factors or are concomitant with the symptoms. This study examines the neuropsychological functioning of a group of adolescent offspring who are at risk for a mood disorder by virtue of being raised by mothers who have been diagnosed with major depressive disorder (MDD) or bipolar disorder (BPD).

METHODS

Adolescent offspring of mothers with BPD (n = 43) or MDD (n = 72) and of psychiatrically well parents (n = 50) completed a battery of neuropsychological tests to assess executive functioning, memory, and attention.

RESULTS

Children of mothers with BPD showed deficits in executive functioning and selective deficits in spatial memory and attention, in comparison with children of well mothers. Deficits were not found for children of MDD mothers.

CONCLUSIONS

Knowledge of these neurocognitive processes could aid ultimately in determining whether neurocognitive deficits precede BPD, whether unique profiles are associated with various types of mood disorders, and who may benefit from interventions.

Specificity of cognitive deficits in bipolar disorder versus schizophrenia. A systematic review

BACKGROUND

More and more epidemiological, genetic and neuroimaging studies show similarities between bipolar disorder (BD) and schizophrenia (SZ). Cognitive functions are known to be highly impaired in SZ and are increasingly studied in BD. When both populations are compared, the conclusions appear to be contradictory. The purpose of this review is to help define the profile of cognitive deficits in BD and in SZ.

METHODS

A systematic review of the literature of neuropsychological studies comparing BD and SZ was made, beginning in January 1990 and ending in January 2005. Thirty-eight studies met the required quality criteria and were included in this review.

RESULTS

Bipolar patients exhibit extensive cognitive abnormalities with a pattern of deficits that is not unique to this disease. However, when compared to schizophrenic patients, bipolar patients demonstrate a lesser degree of deficits, particularly concerning premorbid and current intelligence quotient and perhaps attention, verbal memory and executive functions. When looking into effect sizes, there seem to be different profiles even in studies finding no significant differences.

CONCLUSIONS

The neuropsychological differences reported between both groups could be due to the presence of psychotic features, to environmental factors (stressful events, duration of the disease and number of hospitalisations) and could also be related to differences during the neurodevelopmental phase. Further studies should confirm whether these results are truly related to different neurobiological backgrounds.

Does cognition predict community function only in schizophrenia?: a study of schizophrenia patients, bipolar affective disorder patients, and community control subjects

Cognitive deficits predict functioning in schizophrenia; however, little is known as to whether the association is present in other mental disorders. If specific cognitive deficits uniquely predict functional impairment in schizophrenia the association of select aspects of brain dysfunction with daily living would suggest an intervention target and perhaps a means by which to improve the functioning of schizophrenia patients. The relationship of cognition and functioning was investigated in schizophrenia (n=39), bipolar affective disorder (n=27), and nonpsychiatric control (n=38) participants to determine whether the associations varied across groups. We examined verbal memory, verbal learning, verbal fluency, vigilance, executive functioning, symptomatology, and generalized cognitive functioning for associations with social function. Correlational analyses revealed particular cognitive domains (e.g., verbal memory) to be associated with social functioning in schizophrenia, bipolar, and control subjects; however generalized cognitive function and symptomatology were also associated with social functioning in patients. Multiple regression analyses revealed that in schizophrenia poor verbal memory predicted worse social functioning even after the effects of generalized cognitive dysfunction were considered. Verbal memory indices failed to account for variance in social function in bipolar patients and control subjects after consideration of generalized cognitive function. Bipolar patients with worse planning and problem solving tended to have worse social functioning. Therefore, unlike schizophrenia patients who may fail to process verbally mediated material, bipolar patients' difficulty with logical approaches to problems in daily living may have the greatest impact on their community function.

Cognitive functioning in patients with schizophrenia and bipolar disorder: a quantitative review

OBJECTIVE

Evidence suggests that cognitive functioning in bipolar disorder may be impaired even in euthymic states, but it is unclear if the pattern of deficits is similar to the deficits found in schizophrenia. The aim of this study was to review quantitatively the studies on cognitive performance in schizophrenia and bipolar disorder.

METHODS

Articles for consideration were identified through a literature search in MEDLINE and PsycLIT in the period between 1985 and October 2004, using the keywords "schizophrenia" combined with "bipolar disorder", or "manic-depress*" or "manic" combined with "cogniti*" or "neuropsycholog*". Thirty-one studies were included that: i) evaluated cognitive performance using standardized and reliable neuropsychological testing procedures; ii) compared adult patients with schizophrenia and with bipolar disorder; iii) reported test scores of both patient groups, or exact p-values, t-values, or F-values; and iv) were published as an original article in a peer-reviewed English language journal.

RESULTS

Meta-analyses of all studies indicated that patients with bipolar disorder generally perform better than patients with schizophrenia, but the distribution of effect sizes showed substantial heterogeneity. Results based on a more homogeneous subset of studies that matched patient groups on clinical and demographic characteristics pointed in the same direction, with effect sizes in the moderate range.

CONCLUSIONS

Patients with bipolar disorder show better cognitive performance than patients with schizophrenia, even when matched for clinical and demographic characteristics.

Psychometric properties of the web-based work-readiness cognitive screen used as a neuropsychological assessment tool for schizophrenia

Traditional neuropsychological tests have been essential in understanding the nature and magnitude of the cognitive deficits associated with schizophrenia. However, current health care practices demand a more cost-effective and time-efficient assessment tool. This study investigates the psychometric properties of the work-readiness cognitive screen (WCS), a web-based neuropsychological measure, as a tool for screening cognitive impairment in schizophrenia, and examines diagnostic group differences in cognitive functioning between those with schizophrenia and affective disorders using the WCS. Data from 185 outpatients with schizophrenia or schizoaffective disorder and 29 outpatients with a mood disorder was analyzed in this study. The 185 people with schizophrenia were further divided into higher- and lower-functioning groups to assess cognition as it relates to daily functioning. People with schizophrenia demonstrated cognitive impairment on the WCS measures of attention, working memory, immediate and delayed visual memory, and verbal recognition memory. The higher-functioning schizophrenia group tended to perform better on the WCS cognitive domains than the low-functioning group. Reliability ranged from moderate to high. Working memory was found to be the most significant factor distinguishing diagnostic groups. These preliminary studies suggest that the WCS is a useful, time- and cost-effective cognitive screening measure for schizophrenia.

Neuropsychological functioning in youth with bipolar disorder

BACKGROUND

Little is known about the neuropsychological status of youth with bipolar disorder (BPD) or whether cognitive deficits in this population are accounted for by comorbidity with attention deficit/hyperactivity disorder (ADHD). We compared neuropsychological and academic functioning of youth with and without DSM-IV BPD, controlling for effects of comorbid ADHD.

METHODS

Fifty-seven youth with BPD and 46 healthy control subjects were assessed on a battery of clinical neuropsychological measures including subtests from the Wechsler Intelligence Scales for Children and Adults (Third Editions), the Stroop, the Wisconsin Card Sorting Test, the Rey-Osterreith Complex Figure, an auditory working memory Continuous Performance Test, a measure of verbal learning, and the Wide Range Achievement Test-Third Edition.

RESULTS

Bipolar disorder was associated with impairments on subtests reflecting sustained attention, working memory, and processing speed after controlling for ADHD. Additionally, decrements of moderate effect sizes were found for measures of interference control, abstract problem solving, and verbal learning but did not meet criteria for statistical significance.

CONCLUSIONS

After controlling for ADHD, youth with BPD show neuropsychological deficits similar to impairments found in adults with the disorder. Further studies are needed to understand the clinical implications of these impairments as well as their role in the underlying risk for pediatric BPD.

Neuropsychological dysfunction in bipolar affective disorder: a critical opinion

Data from the imaging literature have led to suggestions that permanent structural brain changes may be associated with bipolar disorder. Individuals diagnosed with bipolar disorder display deficits on a range of neuropsychological tasks in both the acute and euthymic phases of illness, and correlations between experienced number of affective episodes and task performance are commonly reported. These findings have renewed interest in the neuropsychological profile of individuals with bipolar disorder, with deficits of attention, learning and memory, and executive function, asserted to be present. This paper critically reviews five different potential causes of neurocognitive dysfunction in bipolar disorder: (i) iatrogenic, (ii) acute functional changes associated with depression or mania, (iii) permanent structural lesions of a neurodegenerative origin, (iv) permanent structural lesions that are neurodevelopmental in origin, and (v) permanent functional changes that are most likely genetic in origin. Although the potential cognitive effects of residual symptomatology and long-term medication use cannot be entirely excluded, we conclude that functional changes associated with genetically driven population variation in critical neural networks underpin both the neurocognitive and affective symptoms of bipolar disorder. The philosophical implications of this conclusion for neuropsychology are briefly discussed.

When euthymia is just not good enough: the neuropsychology of bipolar disorder

Bipolar disorder (BD) is a debilitating psychiatric illness that is uniquely characterized by switching between psychopathologically contrasting phases of mania and depression, often with intervening periods of euthymia. However, these periods of apparent clinical recovery (euthymia) are marked by subtle social, occupational, and cognitive impairments, profiled by recent neuropsychological investigations. Determining the cognitive changes across these three phases may help differentiate the disruptions that are mood state-dependent from those associated with underlying pathology. This article therefore critically reviews the reported neuropsychological impairments in BD and the methodological limitations facing such research. Integration of the available evidence, principally from the field of neuropsychology, when synthesized, implicates the prefrontal cortex in the etiopathogenesis of BD and posits cortical-subcortical-limbic disruption in recovered euthymic patients that manifests as cognitive dysfunction.

Bipolar disorder: it's all in your mind? The neuropsychological profile of a biological disorder

OBJECTIVE

To compare and contrast the neuropsychological profile of the 3 phases of bipolar disorder (BD) to achieve a better definition of BD and to identify potential state and trait deficits.

METHODS

We conducted a search for English-language papers published in journals from 1965 onward, using the following terms in Medline and Embase: neuropsychology or neuropsychological and BD, depression, mania, and euthymia. We scrutinized suitable subheadings and retrieved familiar papers and literature.

RESULTS

We initially identified more than 100 articles and then excluded reviews and papers that did not directly administer neuropsychological tests. This left 27 papers, which we further examined and the findings of which we tabulated and discussed. Cognitive and executive functioning deficits were found, including set-shifting, verbal fluency, planning, attention, and memory.

CONCLUSIONS

The neuropsychological deficits found in bipolar depression, mania or hypomania, and euthymia provide important insights into the pathophysiology of BD and may, in future studies, form the basis of clinically meaningful subtypes.

Cognitive functioning in schizophrenia and bipolar disorder: comparison of performance on the Repeatable Battery for the Assessment of Neuropsychological Status

Cognitive dysfunction is an important feature of schizophrenia and bipolar disorder. There is uncertainty about the relative magnitude of cognitive deficits in these disorders. We evaluated a total of 446 individuals: 229 with schizophrenia, 117 with bipolar disorder, and 100 controls without a history of psychiatric disorder. All participants were administered the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS), a cognitive screening battery that evaluated immediate verbal memory, visuospatial/constructional abilities, attention, language, and delayed memory. A comparison of the three groups showed significant differences on the RBANS total score and all of the measured domains. In all of the comparisons, the schizophrenia group obtained the lowest scores, followed by the bipolar disorder group, and then the individuals without psychiatric disorder. In an analysis of covariance of RBANS total scores with the patient samples, the difference between schizophrenia and bipolar disorder remained significant after controlling for a range of demographic and clinical variables. Both schizophrenia and bipolar disorder are associated with significant cognitive impairments, but those in schizophrenia are more severe. Cognitive deficits may be an appropriate target of treatment interventions in these disorders.

Cognitive functioning in young people with first episode psychosis: relationship to diagnosis and clinical characteristics

OBJECTIVE

To examine the extent and nature of neuropsychological deficits in adolescents and young people with first episode psychosis (FEP), and to determine whether the pattern and extent of neuropsychological deficits varied according to diagnosis.

METHOD

A total of 83 FEP subjects aged 13-25 years, and 31 healthy controls completed a comprehensive battery of neuropsychological tests, grouped into 10 cognitive domains. First episode psychosis subjects were stratified into three diagnostic groups (schizophrenia, affective disorders, substance-induced psychosis) and differences in cognitive profiles were examined. The contribution of demographic and clinical characteristics to cognitive performance was also explored.

RESULTS

The schizophrenia group demonstrated significantly worse performance on tasks of verbal learning and memory than the affective disorders group. Compared to healthy controls, the schizophrenia group also demonstrated global impairment across the majority of cognitive domains. The substance-induced group's performance lay between that of the schizophrenia and affective disorders groups. Analyses of differential deficits revealed that verbal learning, verbal memory and current intellectual functioning were selectively impaired in the schizophrenia group, whereas the affective disorders group demonstrated a selective deficit in speeded processing. Premorbid intellectual functioning, negative symptomatology and medication levels were the strongest predictors of cognitive performance in FEP subjects.

CONCLUSIONS

Verbal memory deficits differentiate individuals with schizophrenia from those with psychotic affective disorders. Although significant cognitive deficits are evident across all diagnostic FEP groups, individuals with schizophrenia appear to have more generalized impairment across a broad array of cognitive functions than other psychotic diagnoses. Lower premorbid intellectual functioning does not appear to contribute to greater cognitive deterioration following onset of psychosis, but severity of illness may be a more important factor than levels of mood disturbance.

Comparison of neurocognition between drug-free patients with schizophrenia and bipolar disorder

It is often difficult to make a differential diagnosis between schizophrenia and bipolar disorder because of the overlapping symptoms. The patients of both disorders have been shown to have neurocognitive deficits. In this study, a computerized battery of neurocognitive tasks, COGLAB, was administered to four participant groups: 30 patients with positive schizophrenia, 22 patients with negative schizophrenia, 27 patients with bipolar disorder, and 28 normal controls. All the patients were drug-free for at least 1 month. The tasks included Mueller-Lyer illusion, reaction time, size estimation, a variant of the Wisconsin Card Sorting Test, backward masking, and Asarnow continuous performance. Discriminant analyses were used to investigate the differences among the four groups. Results indicated that COGLAB correctly classified 73.5% of the cases of negative schizophrenia and bipolar disorder. The best discriminative tasks were card sort, Asarnow continuous performance, and backward masking. The results of this study were also compared with results of a previous study with medicated patients. Neurocognitive tasks had better discriminative power for medicated patients with schizophrenia and bipolar disorder than for drug-free patients. Moreover, medication effects did not seem to significantly change the pattern of the neurocognitive task responses of patients with schizophrenia.

Neuropsychology of bipolar disorder: a review

BACKGROUND

Bipolar disorder (BD) may be associated with significant and persistent cognitive impairment. The aim of this study was to describe the profile of cognitive deficits in BD at different phases of the illness and determine whether it is different from that of schizophrenia and unipolar (UP) depression.

METHODS

A systematic review of the computerised literature of neuropsychological studies of BD published between 1980 and 2000.

RESULTS

General intellectual function: this was largely preserved in BD. Impairments when present were limited to acute episodes and to performance scores. Attention: attentional abnormalities were seen in symptomatic BD patients and persisted in remission in measures of sustained attention and inhibitory control. Memory: verbal memory was impaired even in euthymic patients while visuo-spatial memory deficits were variable depending on the tasks used. Executive function: all aspects of executive function (planning, abstract concept formation, set shifting) were impaired in symptomatic BD patients. Performance on executive function tests was sensitive to the presence of even residual symptoms but it may be normal in fully recovered patients with uncomplicated BD. Comparison to other patient groups: no major differences in cognitive profile between BD and UP depression were found. Remitted BD patients out-performed stable schizophrenics on most cognitive measures but this advantage disappeared when they were acutely symptomatic.

CONCLUSIONS

Symptomatic BD patients have widespread cognitive abnormalities. Trait related deficits appear to be present in verbal memory and sustained attention. Executive function and visual memory may be also affected at least in some recovered BD patients.

Wisconsin Card Sorting deficits in the offspring of schizophrenics in the New York High-Risk Project

It has been suggested that performance on the Wisconsin Card Sorting Test (WCST) may be an indicator of vulnerability to schizophrenia. WCST deficits have been demonstrated in schizophrenic patients and their relatives, but not as yet in their offspring. This study aimed to further establish the indicator potential of WCST deficits by analyzing data collected as part of the New York High-Risk Project (NYHRP), a longitudinal study of attention, cognition and clinical functioning in the offspring of schizophrenic (HRSz, n=73), affective disordered (HRAff, n=61) and normal comparison (NC, n=120) parents. Parental Research Diagnostic Criteria diagnoses were established by semi-structured interview (SADS-L). WCST testing was carried out when offspring were in their mid-20s. HRSz subjects performed significantly more poorly on the WCST than HRAff and NC subjects. High-risk subjects who developed psychotic symptoms prior to or shortly after testing did not differ significantly from HRSz subjects who did not become ill. Thus, WCST performance in the offspring of schizophrenics resembles that of schizophrenic patients and may distinguish HRSz from offspring at risk for nonschizophrenic illness. WCST deficits may be a specific familial indicator of vulnerability, but appear not to distinguish between those subjects at risk for schizophrenia who do or do not become ill.

Personality dimensions and neuropsychological performance in first-degree relatives of patients with schizophrenia and affective psychosis

Several studies have found a significant increase in the prevalence of some personality disorders in the first-degree relatives of patients with schizophrenia; other studies have found subtle neuropsychological deficits in these relatives. However, little is known about the specificity of the personality traits reported or about the relationship between these traits and the neuropsychological deficits.One-hundred first-degree relatives of patients with schizophrenia (SR) and 88 first-degree relatives of affective psychotic patients (APR) completed the Eysenck Personality Questionnaire which measures extraversion, neuroticism, and psychoticism; they were also administered the National Adult Reading Test (NART), the Trail Making Test (TMT) and a Verbal Fluency Test (VFT). The male relatives of patients with schizophrenia scored significantly higher on the psychoticism scale than the male relatives of affective psychotic patients. In the SR group, there were significant correlations between the TMT performance and the extraversion scores and, between the IQ scores and the psychoticism scores. However, when logistical regression analyses were performed, none of the three personality scores predicted any of the neuropsychological performance in either the SR or the APR group. These results indicate some specificity as well as sex differences in the psychoticism dimension. Moreover, the relationship between the personality dimensions and the neuropsychological performance could indicate that psychoticism increases vulnerability to psychosis whereas extraversion decreases it.

Neuropsychological performance of psychotic patients in community care: results from the UK700 study

OBJECTIVE

To compare cognitive performance in chronic schizophrenic and affective psychotic patients maintained in community care.

METHOD

We studied a sample of community-based patients (n = 707) with chronic psychotic disorders. Neuropsychological assessment was completed using the National Adult Reading Test (NART) and the Trail Making Test (TMT).

RESULTS

Affective psychotic patients had higher premorbid IQ than schizophrenic patients before adjustment for confounding factors (P=0.03); however, after adjustment for ethnic group and social class this became non-significant (P=0.19). There were no significant differences between groups on the TMT, parts A or B.

CONCLUSION

Unlike studies suggesting that schizophrenic patients are more cognitively impaired than affective psychotic patients, our study suggests a degree of cognitive homogeneity between those patients who develop a chronic illness. Measures of premorbid IQ suggest that this cognitive homogeneity exists prior to the onset of illness.

Executive function in patients with remitted bipolar disorder and schizophrenia and its relationship with functional outcome

BACKGROUND

Recent studies have reported that differences in cognitive performance between schizophrenic and bipolar patients seem to be smaller than expected. Patients with schizophrenia have consistently shown frontal executive dysfunctions, but studies regarding executive abilities in bipolar patients are scarce and discrepant. As executive function has been associated with psychosocial functioning in schizophrenia, we wanted to investigate if such a relationship is also present in bipolar disorder and the differences between the two groups.

METHODS

Executive function was assessed in 49 euthymic (at least 6 months in remission, Hamilton Depression Rating Scale < or = 8 and Young Mania Rating Scale < or = 6) bipolar and in 49 schizophrenic, residual-type (with at least 1 year without acute exacerbation and predominant negative symptomatology) patients, by the Wisconsin Card Sorting Test (WCST), FAS Test (COWAT) and Trail Making Test. Baseline clinical and psychosocial variables were controlled and psychopathology evaluated by means of the Positive and Negative Syndrome Scale (PANSS).

RESULTS

The two groups showed a similar pattern of cognitive deficits in tests of executive function, except for the number of categories achieved in the WCST, which was significantly lower in the schizophrenic group (F = 7.26; p = 0.009). Functional outcome was predicted by the negative syndrome (PANSSN) and perseverative errors (WCST) in schizophrenic patients, and general psychopathology (PANSSG) was the best predictor of functional outcome in the bipolar group.

CONCLUSION

Executive function was a good predictor of functional outcome in the schizophrenic group, whereas clinical variables were more predictive of the bipolar one. Patterns of cognitive disturbances in tasks of executive function are similar in both groups but quantitatively more marked in schizophrenia.

A comparative profile analysis of neuropsychological functioning in patients with schizophrenia and bipolar psychoses

Evidence for neuropsychological deficits in schizophrenia is substantial whereas evidence for the specificity of dysfunction is relatively sparse. To assess specificity, we compared neuropsychological function in patients with chronic schizophrenia, patients with chronic psychotic bipolar disorder and normal controls. Groups were comparable on age, ethnicity and expected intellectual ability (based on single word reading). Patients with schizophrenia and bipolar psychoses were also relatively similar on age at onset and number of hospitalizations. Using multivariate analyses of variance with sex and parental SES as covariates (our primary analyses), patients with schizophrenia were significantly more impaired than controls on seven of eight neuropsychological functions (all but verbal ability), and were significantly more impaired than bipolar patients on abstraction, perceptual-motor speed and vigilance. Bipolar patients were significantly impaired compared to controls on declarative verbal memory, and showed moderate-to-large effect size decrements on abstraction, perceptual-motor speed and vigilance. Results were not attenuated when IQ was controlled, which was significantly lower in patients with schizophrenia. Analyses indicated that the two psychiatric groups had similar profile patterns, but that patients with schizophrenia had a more severe impairment than patients with bipolar psychoses. Further research is required to determine whether similar mechanisms underly the neurocognitive deficits in these disorders.

Neuropsychological impairment among manic, depressed, and mixed-episode inpatients with bipolar disorder

Previous research has demonstrated broad neurobehavioral abnormalities in bipolar affective disorder (cf. G. Cassens, L. Wolfe, & M. Zola, 1990). However, there have been no comparisons of neuropsychological function across patients with manic, depressed, or mixed subtypes. In the present study, 37 manic, 24 mixed-episode, and 25 depressed bipolar I inpatients and 34 control subjects were administered a brief battery of neuropsychological tests. The multivariate and univariate effects of participant group on the neuropsychological measures were uniformly significant (p < .05). Planned contrasts revealed that the bipolar participants performed worse than the controls, and few differences existed between the 3 patient groups. Additionally, the bipolar groups were impaired on 50% of the test battery. These abnormalities were unlikely attributable to differences in psychiatric symptomatology, medical illness, comorbid psychiatric diagnoses, or medication status. Findings imply that acute mood disturbance during bipolar disorder yields significant neurobehavioral dysfunction.

The neuropsychology and neuroanatomy of bipolar affective disorder: a critical review

Bearden CE, Hoffman KM, Cannon TD. The neuropsychology and neuroanatomy of bipolar affective disorder: a critical review. Bipolar Disord 2001: 3: 106 150. C Munksgaard, 2001

OBJECTIVES

To present a comprehensive review of the existing neuropsychological and neuroimaging literature on bipolar affective disorder. This review critically evaluates two common conceptions regarding the neuropsychology of bipolar disorder: 1) that, in contrast to schizophrenia, bipolar affective disorder is not associated with general cognitive impairment independent of illness episodes, and 2) relative right hemisphere (RH) dysfunction is implicated in bipolar illness patients, supported by reports of relatively greater impairment in visuospatial functioning, lateralization abnormalities, and mania secondary to RH lesions.

METHODS

The major computerized databases (Medline and PSYCInfo) were consulted in order to conduct a comprehensive, integrated review of the literature on the neuropsychology and neuroanatomy of bipolar disorder. Articles meeting specified criteria were included in this review.

RESULTS

In a critical evaluation of the above notions, this paper determines that: 1) while there is little evidence for selective RH dysfunction, significant cognitive impairment may be present in bipolar illness, particularly in a subgroup of chronic, elderly or multiple-episode patients, suggesting a possible toxic disease process, and 2) the underlying functional correlate of these cognitive deficits may be white matter lesions ('signal hyperintensities') in the frontal lobes and basal ganglia, regions critical for executive function, attention, speeded information processing, learning and memory, and affect regulation. While this hypothesized neural correlate of cognitive impairment in bipolar disorder is speculative, preliminary functional neuroimaging evidence supports the notion of frontal and subcortical hypometabolism in bipolar illness.

CONCLUSIONS

The etiology of the structural brain abnormalities commonly seen in bipolar illness, and their corresponding functional deficits, remains unknown. It is possible that neurodevelopmental anomalies may play a role, and it remains to be determined whether there is also some pathophysiological progression that occurs with repeated illness episodes. More research is needed on first-episode patients, relatives of bipolar probands, and within prospective longitudinal paradigms in order to isolate disease-specific impairments and genetic markers of neurocognitive function in bipolar disorder.

Outpatients with schizophrenia and bipolar I disorder: Do they differ in their cognitive and social functioning?

The authors used a battery of cognitive and social functioning measures to evaluate stable outpatients with schizophrenia (n=74) and bipolar I disorder (n=26) who were receiving care at community and rehabilitation programs. The groups did not differ significantly on 36 of 41 measures. For most variables, comparisons between groups yielded effect sizes of <0.5. These results suggest that individuals with bipolar I disorder receiving community and rehabilitation services have many social and cognitive deficits that are as severe as those in schizophrenia.

Cortical instability and the mechanism of mania: a neural network simulation and perceptual test

BACKGROUND

A previous neural network simulation suggested that manic states arise from excessive levels of noise that destabilize neural representations. The Necker cube stick figure provides a simple perceptual task that assesses stability of gestalt-type representations.

METHODS

A neural network was developed that included a simulation of the Necker cube task. Noise was added to induce maniclike jumps from one representation to another. A parallel study of Necker cube perception was conducted with 16 patients diagnosed with manic-spectrum disorder, 18 patients with schizophrenia, and 19 normal control subjects. Cognitive speed and rate of indiscriminate responses were assessed using an auditory continuous performance task.

RESULTS

During processing of the "Necker cube" stimulus, the reversal rate of the noise-destabilized "manic" network was increased by 30%. In the human subject study, the median score of Necker cube reversal rates for manic-spectrum patients was roughly twice that of normal control subjects and patients with schizophrenia. Accelerated reversal rates in the manic-spectrum group were not attributable to excessive cognitive speed or higher rates of indiscriminate responses.

CONCLUSIONS

The two studies, considered together, support the hypothesis that excessive cortical noise destabilizes neural representations in manic-spectrum patients.

Epidemiology and pathobiology of bipolar disorder, and their exploration within a complete catchment area population

Epidemiological and pathobiological findings in bipolar disorder [BP] have often been limited by selection bias and lack of epidemiological representativeness. In a rural, circumscribed catchment area, 'all' patients with BP were identified and assessed. On preliminary analysis, morbid risk [MR] for BP over the area as a whole was 5.0 ± 0.6/1000. The distribution of MR for BP over geographical subregions showed no significant deviation from a statistical model for random occurrences in space by place at birth, in contrast to schizophrenia [SZ], and varied only modestly among males by place at onset. These results imply different etiological factors acting in BP in comparison with SZ, particularly with regard to the role of early versus later life events. In preliminary analyses of psychotic and cognitive features, current severity of positive symptoms was predicted in BP only by increasing dominance of the left hand; negative symptoms by duration of illness and current anticholinergic exposure; poorer general and frontal cognitive function by older age at onset of illness, increasing duration of illness, and current anticholinergic exposure. The finding on handedness suggests disturbance of cerebral asymmetry associated with positive symptoms in BP, while both negative symptoms and cognitive impairment may involve progressive processes. Further analysis of this epidemiologically complete population, including systematic comparisons of BP with schizoaffective disorder and SZ, continues.

Cognitive function in euthymic bipolar patients, stabilized schizophrenic patients, and healthy controls

Studies on cognitive function in bipolar disorder have led to contrasting results and few data are available on affected subjects during the euthymic phase. In the present study we investigated the cognitive function of a cohort of bipolar (n=40) and schizophrenic (n=66) patients compared to healthy controls (n=64). Patients were evaluated in the outpatient setting over at least 3 months using a computerized version of Wisconsin Card Sorting Test. Schizophrenic patients showed the worst performance while that of the bipolar patients was somewhere between schizophrenic and controls. A discriminant analysis was able to classify correctly 60.59% of the subjects (schizophrenics 48.5%, bipolars 40%; healthy controls 85. 9%). The scores of the Wisconsin Card Sorting Test were entered into a principal component analysis, which yielded a 2-factor solution. Even in that analysis bipolar patients showed intermediate features in comparison with the other groups. These data indicate that bipolar patients have subtle neurocognitive deficits even after the resolution of an affective disorder. As well as observing quantitative differences between groups, the results show different dimensions of cognitive performance within groups suggesting that the deficit of euthymic bipolars could be a dishomogeneous entity, probably more heterogeneous than that in schizophrenia. Studies administering a more complete neuropsychological battery could further clarify the nature and meaning of the cognitive deficits in schizophrenia and bipolar disorder.

Neuropsychological function in subjects with psychotic and affective disorders. Relationship to diagnostic category and duration of illness

OBJECTIVE

To explore the links between neuropsychological performance, diagnostic category and duration of illness in subjects with psychotic and affective disorders.

METHODS

Memory and executive abilities were tested in consecutively admitted patients with schizophrenia (N = 20), other non-schizophrenic psychotic disorders (N = 29), bipolar disorder (N = 33) and major depression (N = 19).

RESULTS

Subjects with schizophrenia had poorer global memory performances than subjects with major depression, and poorer delayed verbal memory abilities than those from the other three diagnostic groups. Executive abilities explored by the Stroop test and the Wisconsin Card Sorting Test did not differ between diagnostic groups. Neuropsychological performances were not influenced by previous duration of illness.

CONCLUSION

Memory deficits are the most discriminatory cognitive features between subjects with schizophrenia and those with other psychotic or mood disorders. The fact that cognitive deficits are static whatever the diagnostic group indirectly suggests that they may have a neurodevelopmental origin in subjects with schizophrenia, but perhaps also in subjects with other psychotic and mood disorders.

Repeatable battery for the assessment of neuropsychological status as a screening test in schizophrenia, II: convergent/discriminant validity and diagnostic group comparisons

OBJECTIVE

In a companion article in this issue of the Journal, the authors presented data suggesting that the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) is sensitive to the types of impairments observed in schizophrenia, correlates highly with standard measures of intelligence and memory, and is related to employment status in a group of patients with schizophrenia drawn from a tertiary care research center. The objectives of the current study were 1) to determine if evidence of the convergent validity of the RBANS could be replicated in a diagnostically heterogeneous sample drawn from a public mental health system, 2) to examine the relationship of the RBANS to a broad neuropsychological battery, and 3) to compare the performance of patients with schizophrenia and patients with bipolar disorder on a neuropsychological battery and the RBANS.

METHOD

The RBANS and a standard neuropsychological battery, including the WAIS-III and Wechsler Memory Scale, 3rd ed. (WMS-III), were given to 150 patients drawn from a larger study of vocational rehabilitation.

RESULTS

Correlations of RBANS total scores with WAIS-III and WMS-III variables were highly similar across study groups. The RBANS correlated highly with a composite z score derived from 22 standard measures of IQ, memory, language, motor, attention, and executive function. Principal component analyses of the neuropsychological battery resulted in a six-factor solution: the RBANS correlated most highly with a general ability factor and had limited correlations with measures of motor performance, vigilance, and executive function. Patients with schizophrenia demonstrated greater deficits on the neuropsychological battery and the RBANS than patients with bipolar disorder.

CONCLUSIONS

These data suggest that the RBANS is a useful screening instrument for assessing the severity of cognitive impairment in psychiatric populations.

Contrasts in memory functions between adolescents with schizophrenia or ADHD

Previous research on memory and schizophrenia has relied on a limited number of global memory measures instead of a comprehensive assessment of various memory components. In addition, little effort has been directed at examining memory functioning in patients with early-onset schizophrenia. Published research often lacks a relevant neuropsychiatric comparison group to control for attention difficulties. Patients with Attention Deficit Hyperactivity Disorder (ADHD) were included in the present study for this purpose. To our knowledge, a direct comparison of the two patient groups on memory functions has never been made. In the present study, both adolescents with schizophrenia and adolescents with ADHD were compared on a comprehensive memory test battery. Nineteen adolescents with schizophrenia were compared to 20 ADHD adolescents and 30 normally functioning adolescents on measures of working memory and long-term episodic memory, including tests of verbal and visual memory, free recall and recognition memory. The performance of the adolescents with schizophrenia was impaired as compared to the normal group on most of the memory measures. They performed significantly more poorly than the adolescents with ADHD on the visual memory tests. The ADHD group scored more impaired than the schizophrenia group on working memory tests with focus on distractibility. The findings suggest a general memory deficit among adolescents with schizophrenia related to both verbal and visual material. Impairment on the measures of visual memory is specific to schizophrenia and does not characterise the ADHD subjects.

Some fairly obvious distinctions between schizophrenia and bipolar disorder

In examining the ratio of 'famous' individuals with bipolar disorder to those with schizophrenia, it is evident that the ratio greatly favors those with bipolar disorder, suggesting that schizophrenia somehow precludes expert performance or high-level accomplishment. Why might this be so? One possible explanation lies in neurocognitive findings. In this review, I suggest that patients with schizophrenia perform consistently worse than patients with bipolar disorder on a variety of higher level cognitive tasks (though bipolar patients themselves often evince impairment in comparison to healthy controls). Working memory, in particular, appears to discriminate between the groups. However, questions remain, including the effects of state and medications, and the conclusion that I reach does not exclude the possibility that the two disorders share some but not all etiologic or pathophysiologic features.

Neuropsychological risk indicators for schizophrenia: a preliminary study of female relatives of schizophrenic and bipolar probands

Evidence of subtle neuropsychological deficits in relatives of schizophrenic probands (REL-SZs) suggests that these are risk indicators for schizophrenia, but little is known about whether neuropsychological performance in REL-SZs differs from that in other groups of relatives. We compared neuropsychological function in female REL-SZs (n = 39), relatives of primarily psychotic bipolar disorder probands (REL-BPs; n = 15), and a normal control group (n = 44). After adjustment for expected intellectual ability (based on reading recognition), REL-SZs showed deficits in verbal and visual memory (Wechsler Memory Scale-Revised logical memories, visual reproductions), and auditory attention (dichotic digits) compared with either REL-BPs or control subjects. Memory, but not dichotic listening differences remained significant after adjusting for current IQ; however, average effect sizes after controlling for either reading or IQ were roughly comparable for these three parameters (d = 0.80, 0.71, and 0.69, respectively). REL-BPs and control subjects showed little difference. Although both schizophrenic and bipolar patients often manifest neuropsychological dysfunction, these preliminary findings indicate subtle neuropsychological deficits only in REL-SZs. Such differences suggest different underlying processes; neuropsychological impairment may, in part, reflect an expression of genetic liability to schizophrenia but not bipolar disorder. Replication with a larger REL-BP sample and with male relatives is needed to evaluate the generalizability of the results.

Neuropsychological dysfunction and clinical outcome in psychiatric disorders: a two-year follow-up study

The presence of neuropsychological disturbances in schizophrenia and mood disorders raises the question that cognitive impairments might contribute to poor outcome. This report examines changes in neuropsychological performance from hospitalization to a 2-year follow-up evaluation in relation to psychosocial outcome. Findings indicated that unfavorable clinical outcome is associated with marginal changes in neuropsychological performance, whereas good outcome status is associated with neuropsychological improvement. Neuropsychological improvement may thus require a stable period of favorable psychosocial recovery, in schizophrenia and schizoaffective disorder, as well as major mood disorder syndromes.

Contrasts in neuropsychological test profile between patients with first-episode schizophrenia and first-episode affective disorders

Patients with first-episode (FE) schizophrenia (n = 27), unipolar depression (n = 10) and bipolar disorder (n = 17) and age- and gender-matched healthy control subjects (n = 27) were administered a battery of neuropsychological (NP) tests. FE schizophrenics performed significantly less well than patients with affective disorders in the area of visual motor processing and attention. Affective disorder patients without psychotic features did not perform significantly differently to controls. However, affective disorder patients with psychotic features performed as poorly as schizophrenics, with the most pronounced impairment in the area of visual motor processing and attention. Our data tentatively suggest the existence of a dichotomy in neuropsychological impairment, with psychotic patients showing similar neuropsychological deficits, while non-psychotic affective patients perform comparably to controls.

Hemispheric asymmetries of function in patients with major affective disorders

Several investigators have suggested that affectively disordered patients have dysfunction of the nondominant cerebral hemisphere. The present study tested this hypothesis using psychometrically matched measures of verbal and visual-spatial skills. A sample of 64 psychiatric in-patients and out-patients was interviewed using an expanded and modified version of the NIMH Diagnostic Interview Schedule and diagnosed using the criteria of DSM-III-R, the Research Diagnostic Criteria, and the Feighner et al. system. Patients diagnosed as affectively disordered by at least one system were administered a pair of psychometrically matched measures: a measure of Word-Finding modeled after the Boston Naming Test, and a measure of visual-spatial functioning adapted from the Dot-Localization task. Patients with diagnoses of major depression by any of the three systems showed significantly poorer performance on Dot Localization than on Word Finding. Differences for patients with bipolar diagnoses were in the same direction but fell short of significance. These results support the hypothesis that patients with major depressive disorders may show impaired right-hemisphere functioning.

Memory function in schizophrenia

Memory impairment in schizophrenia has been reported in several studies during the last decades. Issues related to the interpretation of such deficits are discussed. Research strongly suggests specific memory dysfunction in schizophrenia that may be neither drug induced nor secondary consequences of attentional disorders. Our own longitudinal data indicate that these deficits deviate from normal function in a relatively stable way. Although medial temporal lobe structures seems to be of special importance, memory function may be vulnerable to a variety of neurobiological abnormalities.

Cognitive disorders and negative symptoms as correlates of motivational deficits in psychotic patients

The problem of a possible lack of motivation to perform cognitive tasks, which is often encountered in psychotic patients, has been approached from the perspective of the 'energetics' of cognition (Hockey et al. 1986) and from the broader clinical context of psychosis as an 'amotivational syndrome' and its related negative symptoms. The presence of motivational deficits was investigated in a group of psychotic in-patients (N = 73, and 40 had schizophrenia) compared with a control group of non-psychotic psychiatric in-patients (N = 23). The motivational deficit was operationalized in terms of Sanders's (1983) cognitive-energetic model as a large effect of 'time-on-task' during a simple, monotonous reaction test. Significantly more psychotic patients than control patients showed evidence of this type of motivational deficit. The deficit appeared to be related with negative but not with positive symptoms of psychosis. Furthermore, the deficit was shown to be related to the cognitive disorders of psychosis, which have been amply documented in the literature, i.e. disorders of vigilance, verbal memory and distractibility. These results suggest that the cognitive disorders of psychosis are not of a 'computational' but of an 'energetical', i.e. motivational nature.