Some fairly obvious distinctions between schizophrenia and bipolar disorder

Supra-second interval timing in bipolar disorder: examining the role of disorder sub-type, mood, and medication status

BACKGROUND

Widely reported by bipolar disorder (BD) patients, cognitive symptoms, including deficits in executive function, memory, attention, and timing are under-studied. Work suggests that individuals with BD show impairments in interval timing tasks, including supra-second, sub-second, and implicit motor timing compared to the neuronormative population. However, how time perception differs within individuals with BD based on disorder sub-type (BDI vs II), depressed mood, or antipsychotic medication-use has not been thoroughly investigated. The present work administered a supra-second interval timing task concurrent with electroencephalography (EEG) to patients with BD and a neuronormative comparison group. As this task is known to elicit frontal theta oscillations, signal from the frontal (Fz) lead was analyzed at rest and during the task.

RESULTS

Results suggest that individuals with BD show impairments in supra-second interval timing and reduced frontal theta power during the task compared to neuronormative controls. However, within BD sub-groups, neither time perception nor frontal theta differed in accordance with BD sub-type, depressed mood, or antipsychotic medication use.

CONCLUSIONS

This work suggests that BD sub-type, depressed mood status or antipsychotic medication use does not alter timing profile or frontal theta activity. Together with previous work, these findings point to timing impairments in BD patients across a wide range of modalities and durations indicating that an altered ability to assess the passage of time may be a fundamental cognitive abnormality in BD.

Use of multiple polygenic risk scores for distinguishing schizophrenia-spectrum disorder and affective psychosis categories in a first-episode sample; the EU-GEI study

BACKGROUND

Schizophrenia (SZ), bipolar disorder (BD) and depression (D) run in families. This susceptibility is partly due to hundreds or thousands of common genetic variants, each conferring a fractional risk. The cumulative effects of the associated variants can be summarised as a polygenic risk score (PRS). Using data from the EUropean Network of national schizophrenia networks studying Gene-Environment Interactions (EU-GEI) first episode case-control study, we aimed to test whether PRSs for three major psychiatric disorders (SZ, BD, D) and for intelligent quotient (IQ) as a neurodevelopmental proxy, can discriminate affective psychosis (AP) from schizophrenia-spectrum disorder (SSD).

METHODS

Participants (842 cases, 1284 controls) from 16 European EU-GEI sites were successfully genotyped following standard quality control procedures. The sample was stratified based on genomic ancestry and analyses were done only on the subsample representing the European population (573 cases, 1005 controls). Using PRS for SZ, BD, D, and IQ built from the latest available summary statistics, we performed simple or multinomial logistic regression models adjusted for 10 principal components for the different clinical comparisons.

RESULTS

In case-control comparisons PRS-SZ, PRS-BD and PRS-D distributed differentially across psychotic subcategories. In case-case comparisons, both PRS-SZ [odds ratio (OR) = 0.7, 95% confidence interval (CI) 0.54-0.92] and PRS-D (OR = 1.31, 95% CI 1.06-1.61) differentiated AP from SSD; and within AP categories, only PRS-SZ differentiated BD from psychotic depression (OR = 2.14, 95% CI 1.23-3.74).

CONCLUSIONS

Combining PRS for severe psychiatric disorders in prediction models for psychosis phenotypes can increase discriminative ability and improve our understanding of these phenotypes. Our results point towards the potential usefulness of PRSs in specific populations such as high-risk or early psychosis phases.

Transdiagnostic comparison of visual working memory capacity in bipolar disorder and schizophrenia

BACKGROUND

Impaired working memory is a core cognitive deficit in both bipolar disorder and schizophrenia. Its study might yield crucial insights into the underpinnings of both disorders on the cognitive and neurophysiological level. Visual working memory capacity is a particularly promising construct for such translational studies. However, it has not yet been investigated across the full spectrum of both disorders. The aim of our study was to compare the degree of reductions of visual working memory capacity in patients with bipolar disorder (PBD) and patients with schizophrenia (PSZ) using a paradigm well established in cognitive neuroscience.

METHODS

62 PBD, 64 PSZ, and 70 healthy controls (HC) completed a canonical visual change detection task. Participants had to encode the color of four circles and indicate after a short delay whether the color of one of the circles had changed or not. We estimated working memory capacity using Pashler's K.

RESULTS

Working memory capacity was significantly reduced in both PBD and PSZ compared to HC. We observed a small effect size (r = .202) for the difference between HC and PBD and a medium effect size (r = .370) for the difference between HC and PSZ. Working memory capacity in PSZ was also significantly reduced compared to PBD with a small effect size (r = .201). Thus, PBD showed an intermediate level of impairment.

CONCLUSIONS

These findings provide evidence for a gradient of reduced working memory capacity in bipolar disorder and schizophrenia, with PSZ showing the strongest degree of impairment. This underscores the importance of disturbed information processing for both bipolar disorder and schizophrenia. Our results are compatible with the cognitive manifestation of a neurodevelopmental gradient affecting bipolar disorder to a lesser degree than schizophrenia. They also highlight the relevance of visual working memory capacity for the development of both behavior- and brain-based transdiagnostic biomarkers.

White matter aberrations and age-related trajectories in patients with schizophrenia and bipolar disorder revealed by diffusion tensor imaging

Supported by histological and genetic evidence implicating myelin, neuroinflammation and oligodendrocyte dysfunction in schizophrenia spectrum disorders (SZ), diffusion tensor imaging (DTI) studies have consistently shown white matter (WM) abnormalities when compared to healthy controls (HC). The diagnostic specificity remains unclear, with bipolar disorders (BD) frequently conceptualized as a less severe clinical manifestation along a psychotic spectrum. Further, the age-related dynamics and possible sex differences of WM abnormalities in SZ and BD are currently understudied. Using tract-based spatial statistics (TBSS) we compared DTI-based microstructural indices between SZ (n = 128), BD (n = 61), and HC (n = 293). We tested for age-by-group and sex-by-group interactions, computed effect sizes within different age-bins and within genders. TBSS revealed global reductions in fractional anisotropy (FA) and increases in radial (RD) diffusivity in SZ compared to HC, with strongest effects in the body and splenium of the corpus callosum, and lower FA in SZ compared to BD in right inferior longitudinal fasciculus and right inferior fronto-occipital fasciculus, and no significant differences between BD and HC. The results were not strongly dependent on age or sex. Despite lack of significant group-by-age interactions, a sliding-window approach supported widespread WM involvement in SZ with most profound differences in FA from the late 20 s.

A comparative diffusion tensor imaging study of corpus callosum subregion integrity in bipolar disorder and schizophrenia

Structural magnetic resonance imaging (MRI) studies have provided evidence for corpus callosum (CC) white matter abnormalities in bipolar disorder (BD) and schizophrenia (SZ). These findings include alterations in shape, volume, white matter intensity and structural integrity compared to healthy control populations. Although CC alterations are implicated in both SZ and BD, no study of which we are aware has investigated callosal subregion differences between these two patient populations. We used diffusion tensor imaging (DTI) to assess CC integrity in patients with BD (n=16), SZ (n=19) and healthy controls (HC) (n=24). Fractional anisotropy (FA) of CC subregions was measured using region of interest (ROI) analysis and compared in the three groups. Significant group differences of FA values were revealed in five CC subregions, including the anterior genu, middle genu, posterior genu, posterior body and anterior splenium. FA values of the same subregions were significantly reduced in patients with SZ compared with HC. FA values were also significantly reduced in patients with BD compared to the HC group in the same subregions, excepting the middle genu. No significant difference was found between patient groups in any region. Most of the alterations in CC subregions were present in both the BD and SZ groups. These results imply an overlap in potential pathology, possibly relating to risk factors common to both disorders. The one region that differed between patient groups, the middle genu area, may serve as an illness marker and is perhaps involved in the different cognitive impairments observed in BD and SZ.

Discrimination within Recognition Memory in Schizophrenia

Episodic memory is one of the most affected cognitive domains in schizophrenia. First-degree biological relatives of individuals with schizophrenia also have been found to exhibit a similar, but milder, episodic memory deficit. Unlike most studies that focus on the percent of previously presented items recognized, the current investigation sought to further elucidate the nature of memory dysfunction associated with schizophrenia by examining the discrimination of old and new material during recognition (measured by d') to consider false recognition of new items. Using the Recurring Figures Test and the California Verbal Learning Test (CVLT), we studied a sample of schizophrenia probands and the first-degree biological relatives of patients with schizophrenia, as well as probands with bipolar disorder and first-degree biological relatives to assess the specificity of recognition memory dysfunction to schizophrenia. The schizophrenia sample had poorer recognition discrimination in both nonverbal and verbal modalities; no such deficits were identified in first-degree biological relatives or bipolar disorder probands. Discrimination in schizophrenia and bipolar probands failed to benefit from the geometric structure in the designs in the manner that controls did on the nonverbal test. Females performed better than males in recognition of geometric designs. Episodic memory dysfunction in schizophrenia is present for a variety of stimulus domains and reflects poor use of item content to increase discrimination of old and new items.

Social cognition in bipolar disorder versus schizophrenia: comparability in mental state decoding deficits

OBJECTIVES

Neuropsychological studies comparing patients with bipolar disorder (BD) to patients with schizophrenia (SZ) suggest milder cognitive deficits in BD patients and across a smaller range of functions. The present study investigated whether this pattern is also true for social cognition - a range of socially relevant abilities, including emotion perception and recognition, theory of mind, and social attributions - by comparing performance on measures of social cognition in patients with BD, SZ, and healthy participants.

METHODS

One hundred and two patients with BD, 208 patients with SZ, and 132 healthy participants were assessed using a battery of tasks measuring basic neuropsychological and social cognition.

RESULTS

We observed significant differences between patients with BD and healthy participants in a test of mental state decoding ('eyes task') that was at a level comparable to deficits seen in patients with SZ. By comparison, BD patients showed more subtle deficits in mental state reasoning ('hinting task') than those shown by patients with SZ.

CONCLUSIONS

Mental state decoding difficulties are significant in BD. An important direction for further research will be to establish to what extent these deficits affect social and occupational functioning as a potential target for therapeutic intervention.

Shared impairment in associative learning in schizophrenia and bipolar disorder

BACKGROUND

Schizophrenia (SCZ) and bipolar disorder (BD) share some cognitive commonalities. However, the role of associative learning, which is a cornerstone of human cognition mainly relying on hippocampus, has been under-investigated. We assessed behavioral performance during associative learning in a group of SCZ, BD and healthy controls (HC).

METHODS

Nineteen patients with SCZ (36 ± 8.1 years; 13 males, 6 females; all Caucasians), 14 patients with BD (41 ± 9.6 years; 5 males, 9 females; all Caucasians) and 45 HC (27.7 ± 6.9 years; 18 males, 27 females; all Caucasians) were studied. Learning was assessed using an established object-location paired-associative learning paradigm. Subjects learned associations between nine equi-familiar common objects and locations in a nine-location grid. Performance data were analyzed in a repeated measures analysis of variance with time (repeated) and group as factors.

RESULTS

Learning curves (performance = (1-e(-k x time)) fitted to average performance data in the three groups revealed lower learning rates in SCZ and BD (k = 0.17 and k = 0.34) than HC (k = 0.78). Significant effects of group (F = 11.05, p < 0.001) and time (F = 122.06, p < 0.001) on learning performance were observed.

CONCLUSIONS

Our study showed that associative learning is impaired in both SCZ and BD, being potentially not affected by medication. Future studies should investigate the neural substrates of learning deficits in SCZ and BD, particularly focusing on hippocampus function and glutamatergic transmission.

Emotional modulation of response inhibition in stable patients with bipolar I disorder: a comparison with healthy and schizophrenia subjects

OBJECTIVES

Bipolar disorder (BD) has been associated with impairment in affective processing during depressive and manic states; however, there are limited data as to whether this population exhibits such difficulty during stable periods. We examined the pattern of affective processing in stable BD patients and compared their profile to that of healthy controls (HC) and patients diagnosed with schizophrenia (SZ).

METHODS

A total of 336 subjects were administered an Affective Go/No-go test to evaluate target detection of negatively valenced, positively valenced, and neutral stimuli. Accuracy and response bias served as dependent variables in a series of multivariate analyses of covariance to test for group differences.

RESULTS

The BD group relative to the HC group exhibited response biases toward negatively valenced information (p<0.01). Deficits were also evident in discrimination of and accurate responses to positively valenced information in the BD group versus the HC group (p<0.05). In contrast to the controls, the SZ group performed poorly on all task components and was less accurate across all conditions regardless of affective valence (p<0.01). Patients with SZ evidenced reverse biases for positive information, as they were less likely to respond to positive words (p<0.05) despite comparable response bias on neutral and negative conditions.

CONCLUSIONS

Affective processing impairment evident in BD is a feature of the disorder that is present even during stable periods. Prior studies comparing BD with SZ have highlighted clear quantitative but inconsistent qualitative differences in cognitive functioning. Our data suggest that a response bias toward negative stimuli may be a critical and relatively specific feature of BD.

Cognitive functioning in subjects with recent-onset psychosis from a low-middle-income environment: multiple-domain deficits and longitudinal evaluation

Cognitive deficits are a key feature of recent-onset psychosis, but there is no consensus on whether such deficits are generalized or confined to specific domains. Besides, it is unclear whether cognitive deficits: a) are found in psychotic patients in samples from outside high-income countries; and b) whether they progress uniformly over time in schizophrenia and affective psychoses. We applied 12 tests organized into eight cognitive domains, comparing psychosis patients (n = 56, time from initial contact = 677.95+/-183.27 days) versus healthy controls (n=70) recruited from the same area of São Paulo, Brazil. Longitudinal comparisons (digit span and verbal fluency) were conducted between a previous assessment of the subjects carried out at their psychosis onset, and the current follow-up evaluation. Psychosis patients differed significantly from controls on five domains, most prominently on verbal memory. Cognitive deficits remained detectable in separate comparisons of the schizophrenia subgroup and, to a lesser extent, the affective psychosis subjects against controls. Longitudinal comparisons indicated significant improvement in schizophrenia, affective psychoses, and control subjects, with no significant group-by-time interactions. Our results reinforce the view that there are generalized cognitive deficits in association with recent-onset psychoses, particularly of non-affective nature, which persist over time.

Familiarity and recollection processes in patients with recent-onset schizophrenia and their unaffected parents

Episodic memory deficits are present in patients with schizophrenia (SZ) and their unaffected relatives and could be considered as a cognitive indicator of genetic vulnerability to SZ. The present study, involving patients with SZ as well as their parents, used experimental tasks specifically designed to disentangle the contribution of familiarity and recollection processes to episodic memory. The performance of patients with SZ (n=26) and their unaffected parents (n=35) was compared with that of healthy control groups matched on socio-demographic variables (controls of patients, n=26; controls of parents, n=35) on two memory tasks assessing recollection and familiarity. The first task was designed to investigate item recognition and memory for item-spatial context associations whereas the second targeted item-item associations. The results revealed an overall episodic memory deficit in patients with SZ, encompassing both familiarity and recollection, while unaffected parents showed a dysfunction restricted to the recollection process. Our study highlights differences and similarities in the source of the episodic memory deficit found in patients with SZ and their unaffected parents, and it suggests that recollection could act as a cognitive endophenotype of SZ. The results also suggest that use of experimental tasks represents a promising method in the search of cognitive endophenotypes in SZ.

Corpus callosum size and shape in first-episode affective and schizophrenia-spectrum psychosis

Reductions in the size of the anterior callosum have been described for both first-episode and established schizophrenia and bipolar affective disorder, but never in individuals with psychotic bipolar disorder. We recruited 110 first-episode psychosis subjects (74 schizophrenia spectrum and 36 affective psychosis) and 36 age- and gender-matched controls. The callosum was extracted from a mid-sagittal slice from T1-weighted magnetic resonance images, and total area, length and curvature of the callosum were compared. The schizophrenia-spectrum group showed reductions in thickness of the genu across schizophreniform and schizoaffective disorder and schizophrenia, and the schizoaffective disorder group also showed an increase in thickness in the splenium and isthmus. None of these changes were seen in the affective disorder group, although a non-significant increase in the region of the isthmus and splenium was seen, particularly in the depressed group. Psychotic affective disorders do not show the anterior callosal reductions that are seen in the schizophrenia-spectrum group at first episode. The schizoaffective patients show additional posterior callosal expansions that may be a marker of an affective diathesis. This suggests that schizoaffective disorder may represent two interacting illness processes or be mid-way along a continuum of these two broad categories of illness at first psychosis.

Cognitive functioning of bipolar I patients and relatives from families with or without schizophrenia or schizoaffective disorder

BACKGROUND

Bipolar I disorder patients show cognitive impairments, and genetic vulnerability to other psychotic disorders may modify these impairments. We set out to assess cognitive functions and estimate their heritability in bipolar I disorder patients (bipolar families) and unaffected relatives in a group of families with bipolar I disorder only and in another group of families with both bipolar I disorder and schizophrenia or schizoaffective disorder (mixed families).

METHODS

A neuropsychological test battery was administered to 20 bipolar patients and 36 relatives from bipolar families, 19 bipolar patients and 28 relatives from mixed families and 55 controls, all representing population-based samples.

RESULTS

Irrespective of the family group, patients and relatives were impaired in psychomotor processing speed. Both patient groups were impaired in executive functioning, but the deficit was more severe in patients from mixed families. Patients from bipolar families scored lower than controls in nearly all measures of verbal memory. All relatives were slightly impaired in executive functioning. The heritability of cognitive functions was generally similar irrespective of psychopathology in the family. However, there were greater genetic effects in several cognitive tasks in mixed families.

LIMITATIONS

The small sample size and familial type of bipolar disorder could limit the generalizability of the results.

CONCLUSION

Impaired psychomotor processing speed and executive functions may represent markers of susceptibility to bipolar I disorder irrespective of psychopathology within the family. Generalized impairment in verbal memory, in turn, may associate more with bipolar disorder than to vulnerability to other psychotic disorders.

Identifying patient-relevant endpoints among individuals with schizophrenia: An application of patient-centered health technology assessment

Objectives:Schizophrenia imposes a great burden on society, and while evaluation should play an important role in informing society's efforts to alleviate these burdens, it is unclear what “endpoints” should be chosen as the objective of such analyses. The objectives of the study were to elicit endpoints directly from patients with schizophrenia, to ascertain whether patients are sufficiently cognoscente to express what endpoints are and are not important to them and to rank the relevant endpoints.

Methods:We applied principles of patient-centered health technology assessment to identify and value endpoints from the patient's perspective. Focus groups were conducted to elicit endpoints, using interpretive phenomalogical analysis (IPA) to guide the collection, analysis and interpretation of data. Patient interviews were subsequently used to elicit patient preference over endpoints. Respondents were presented with cards outlining the endpoints and asked to remove irrelevant cards. They where then asked to identify and rank their five most relevant endpoints in order of importance. Interviews were recorded for the purposed of triangulation, and data was analyzed using descriptive statistics. Patients were recruited from five geographically diverse cities in Germany. Eligibility required a diagnosis of schizophrenia by a physician and treatment with an antipsychotic medication for at least one year. Respondents were excluded if they were experiencing an acute episode.

Results:Thirteen endpoints emerged as important from the focus groups spanning side-effects, functional status, processes of care and clinical outcomes. Respondents could clearly identify relevant and irrelevant endpoints, and rank which factors were important to them. Triangulation between field notes of the ranking exercise and recordings confirmed that rankings were not arbitrary, but justified from the respondents' point of view.

Conclusions:Patients with schizophrenia can express preferences over endpoints. Our results show that qualitative methods such as IPA can be used to identify factors, but ranking exercises provide a more robust method for ranking the importance of endpoints. Future research involving patients with schizophrenia ranking outcomes is needed to identify variations across patients and methods such as conjoint analysis could prove beneficial in identifying acceptable tradeoffs across endpoints.

Neurocognitive impairment in middle-aged and older adults with bipolar disorder: comparison to schizophrenia and normal comparison subjects

BACKGROUND

The frequency, pattern, and correlates of neurocognitive impairment in older patients with bipolar disorder have received little study. We examined neurocognitive abilities in middle-aged and older adults with bipolar disorder to groups with schizophrenia or normal subjects, as well as the relation of neurocognition to clinical characteristics.

METHOD

We administered a battery of neurocognitive and clinical measures to older (45-85 years) outpatients with bipolar disorder (n=67), schizophrenia (n=150), and normal comparison subjects (n=85). Within the bipolar group, we assessed the association between neurocognitive performance and psychiatric symptoms, quality of life, and medication status.

RESULTS

The group with bipolar disorder differed on nearly all neuropsychological tests compared to normal subjects, with medium effect sizes. Bipolar patients as impaired as those with schizophrenia on half of the tests administered, and performed better on the remaining tests, with small effect sizes. Neurocognitive deficits in bipolar disorder group related to lower quality of life, but not to psychiatric symptom severity or duration of illness.

LIMITATIONS

Samples were outpatients with mild-moderate symptoms, and findings may not generalize to acutely ill populations. We lacked data on illness history to examine the cumulative impact of psychopathology.

CONCLUSIONS

Among clinically stable middle-aged and older outpatients, bipolar disorder was associated with substantial neurocognitive impairment, with a pattern that was somewhat distinct from that found in schizophrenia. Deficits in the bipolar group were not related to severity or duration of psychiatric symptoms, but were related to quality of life. Bipolar disorder often involve disabling and enduring cognitive impairments in older outpatients.

Neuropsychological functioning in bipolar disorder and schizophrenia

BACKGROUND

Some patients with bipolar disorder (BD) demonstrate neuropsychological deficits even when stable. However, it remains unclear whether these differ qualitatively from those seen in schizophrenia (SZ).

METHODS

We compared the nature and severity of cognitive deficits shown by 106 patients with SZ and 66 patients with BD to 316 healthy adults (NC). All participants completed a cognitive battery with 19 individual measures. After adjusting their test performance for age, sex, race, education, and estimated premorbid IQ, we derived regression-based T-scores for each measure and the six cognitive domains.

RESULTS

Both patient groups performed significantly worse than NCs on most (BD) or all (SZ) cognitive tests and domains. The resulting effect sizes ranged from .37 to 1.32 (mean=.97) across tests for SZ patients and from .23 to .87 (mean=.59) for BD patients. The Pearson correlation of these effect sizes was .71 (p<.001).

CONCLUSIONS

Patients with bipolar disorder suffer from cognitive deficits that are milder but qualitatively similar to those of patients with schizophrenia. These findings support the notion that schizophrenia and bipolar disorder show greater phenotypic similarity in terms of the nature than severity of their neuropsychological deficits.

Neuropsychological symptom dimensions in bipolar disorder and schizophrenia

BACKGROUND

While neurocognitive (NC) impairments have been well documented in schizophrenia (SZ), there is limited data as to whether similar impairments are present in other persistent mental illnesses. Recent data indicate that NC impairments may be manifested in bipolar disorder (BPD) and that they persist across disease states, including euthymia. An important question is whether a comparable structure of NC impairments is present in the 2 diagnostic groups.

OBJECTIVE

In a previous factor analytic study, we identified 6 factors to describe the basic underlying structure of neuropsychological (NP) functioning in SZ: Attention, Working Memory, Learning, Verbal Knowledge, Non-Verbal Functions, Ideational Fluency. The goal of this study was to investigate whether this factor structure is generalizable for BPD.

METHODS

The BPD sample included patients (n = 155) from an ongoing longitudinal study evaluating BPD at the time of hospitalization for relapse and at multiple time points over the following 2 years. The SZ sample included patients (n = 250) from a 3-year study. For the current examination the baseline NP evaluations were selected for both samples.

RESULTS

Exploratory and confirmatory factor analyses in the BPD sample yielded factors similar to those identified in the SZ sample. The coefficients of congruence ranged between 0.66-0.90 for the individual factors, indicating a good overall correspondence between the factor structures in the 2 diagnostic groups. Analysis of covariance (ANCOVA) analysis with education level, full scale-IQ, gender and ethnicity as covariates indicated that SZ patients had markedly worse performance on the Attention and Non-Verbal Functioning factors compared to the BPD patients.

CONCLUSIONS

Together, these data suggest that while the same underlying factor structure describes NP functioning in both groups, the profile of impairments appears to vary with the diagnosis.

Rational approaches to the neurobiologic study of youth at risk for bipolar disorder and suicide

OBJECTIVES

The aims of this paper are to provide an overview of neuroimaging findings specific to bipolar disorder and suicide, and to consider rational approaches to the design of future in vivo studies in youth at risk.

METHODS

Neuroimaging and related neurobiological literature pertaining to bipolar disorder and suicide in adult and pediatric samples was reviewed in a non-quantitative manner.

RESULTS

Specific structural and functional brain findings in bipolar disorder are described, where possible in the context of relevant current neurobiological theories of etiology. Diagnostic and prognostic implications are discussed.

CONCLUSIONS

The simultaneous use of complementary neurobiological approaches may be a powerful way of identifying and validating factors reliably associated with bipolar disorder and suicide. A profile of neurobiological markers with which to screen for bipolar disorder and suicide risk may provide for earlier and more accurate diagnosis, perhaps even in the pre- or subsyndromal stages in high-risk youth.

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.

The Maudsley Family Study: premorbid and current general intellectual function levels in familial bipolar I disorder and schizophrenia

The distinction of psychosis into schizophrenia and bipolar disorder has been increasingly challenged with some evidence suggesting that the two conditions may have common etiologic and pathogenic mechanisms. We compared the premorbid and current intellectual function of bipolar patients from multiply affected families, and those of their first-degree relatives, with those of a similar series of schizophrenic subjects, as well as their relatives, and normal controls. Only schizophrenic subjects showed lower premorbid IQ, suggesting that they, but not the bipolar patients or either relative group, had suffered neurodevelopmental impairment. However, both groups of patients had comparably poor current general intellectual levels, implying that some common pathogenic process operates once illness has begun. The two groups of relatives showed distinct differences in intellectual function but we cannot exclude the possibility that these were a function of our sampling methods.

Spatial working memory and planning ability: contrasts between schizophrenia and bipolar I disorder

Working memory may be conceptualized as a multi-component system involving the active maintenance and manipulation of stored information in the service of planning/guiding behaviour. Impaired spatial working memory is a robust finding in schizophrenia patients which has been related to an impairment in frontostriatal connectivity. The purpose of this study was to examine the specificity of this impairment by comparing the mnemonic and executive aspects of working memory performance in schizophrenia and bipolar disorder with psychotic features, focusing particularly on the functional dynamics between task components. Twenty-four patients with schizophrenia, 14 patients with bipolar I disorder (manic phase) and 33 healthy control subjects were assessed using the Cambridge Neuropsychological Test Automated Battery (CANTAB): including the spatial working memory (between search errors and strategy scores) spatial span (storage capacity) and spatial planning (Stockings of Cambridge: accuracy and latency) tasks. Both patient groups were impaired on the spatial span task, which requires the maintenance and retrieval of stored information. In contrast, only schizophrenia patients showed a significant deficit in between search errors, which requires both maintenance and manipulation of information in working memory. That is, they exhibited both a mnemonic and an executive dysfunction. Spatial span was particularly important to accurate planning ability in bipolar patients. In contrast, in patients with schizophrenia poor spatial working memory was a significant predictor of planning impairments, consistent with failures in goal selection, evaluation and/or execution. Furthermore, initial planning time was positively correlated with the latency to complete a planning sequence. This pattern of slow cognitive processing in schizophrenia patients only, resembled that reported previously in patients with basal ganglia disorders. These findings are discussed in terms of a possible common disturbance in fronto-parietal circuitry in the two disorders together with a specific disturbance of fronto-striatal circuitry in schizophrenia, that is not present in bipolar disorder.

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.

Are there attentional deficits in people putatively at risk for affective disorders?

BACKGROUND

Schizophrenia is associated with attentional dysfunctions. In bipolar disorder, there is also evidence for sustained attention deficits. Therefore, we hypothesized that risk for bipolar disorder but not for unipolar depression might be associated with attentional abnormalities as well.

METHOD

Using the Hypomanic Personality Scale (HPS) and the Rigidity Scale, we defined three groups: bipolar at-risk (n=42), unipolar at-risk (n=34), and control (n=37). All completed the d2 Test and the Continuous Performance Test (CPT).

RESULTS

There was no evidence for overall attentional deficits in people at risk for affective disorders. However, reduced sensitivity, i.e., less discrimination between targets and nontargets, was observed in people at risk for bipolar disorders who also displayed schizotypy.

LIMITATIONS

We only looked at selective and sustained attention and did not assess other factors such as memory or executive functions. Additionally, the risk status was only defined by a psychometric indicator and did not include other approaches of defining risk (e.g., first-degree relatives).

CONCLUSIONS

Despite some limitations, our results support on one hand the idea that vulnerability for bipolar disorder can be associated with cognitive impairments, but they also highlight that this is not generally the case. Vulnerability for bipolar disorder and schizotypy might be correlated but are not the same.

A developmental model for similarities and dissimilarities between schizophrenia and bipolar disorder

Schizophrenia and mania have a number of symptoms and epidemiological characteristics in common, and both respond to dopamine blockade. Family, twin and molecular genetic studies suggest that the reason for these similarities may be that the two conditions share certain susceptibility genes. On the other hand, individuals with schizophrenia have more obvious brain structural and neuropsychological abnormalities than those with bipolar disorder; and pre-schizophrenic children are characterised by cognitive and neuromotor impairments, which are not shared by children who later develop bipolar disorder. Furthermore, the risk-increasing effect of obstetric complications has been demonstrated for schizophrenia but not for bipolar disorder. Perinatal complications such as hypoxia are known to result in smaller volume of the amygdala and hippocampus, which have been frequently reported to be reduced in schizophrenia; familial predisposition to schizophrenia is also associated with decreased volume of these structures. We suggest a model to explain the similarities and differences between the disorders and propose that, on a background of shared genetic predisposition to psychosis, schizophrenia, but not bipolar disorder, is subject to additional genes or early insults, which impair neurodevelopment, especially of the medial temporal lobe.

A pilot study of visual backward masking performance among affected versus unaffected offspring of parents with bipolar disorder

BACKGROUND

Cognitive dysfunction is evident in some euthymic patients with established bipolar disorder (BD), including deficits in visual backward masking (VBM) tasks which map to a specific neural pathway. A high-risk paradigm would clarify the temporal relation of cognitive dysfunction to clinical course.

METHOD

We compared euthymic offspring (age range: 18-32 years) of lithium-responsive bipolar parents with and without a previous lifetime history of psychiatric illness to healthy comparison subjects with a negative family history, on a VBM task that requires target location.

RESULTS

High-risk offspring with no lifetime psychiatric history performed the VBM task at levels of healthy controls. High-risk offspring with a previous history of a mood disorder, in complete remission, made significantly more errors at short target-mask intervals than control or never ill offspring. These higher error rates were not a consequence of faster response times.

CONCLUSIONS

There is preliminary evidence of specific cognitive dysfunction early in the course of illness in affected offspring of parents with lithium responsive BD. VBM is ideal for future longitudinal studies addressing whether cognitive dysfunction in BD is a trait marker or a consequence of illness manifestation.

[Executive function remediation in schizophrenia: possible strategies and methods]

AIM AND METHOD

The paper is a selective review of the literature on strategies and methods of cognitive remediation in schizophrenic disorders. It has been focused on the remediation of executive functions and the present hypotheses about the possibility of an improvement of the neurocognitive deficit through specific interventions.

RESULTS AND CONCLUSIONS

People with Schizophrenic Disorders have some degree of cognitive deficit that often precede the clinical onset not secondary to the pathology characteristics persisting even when the positive symptoms have been resolved. The possibility that the neurocognitive deficits could be modified by psychological remediation with effects not exclusively confined to the cognitive domain has been nowadays accepted and numerous studies demonstrate that these interventions are effective and durable with a positive impact on social and working abilities, symptomatology and self-esteem.

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.

Executive dysfunctions as potential markers of familial vulnerability to bipolar disorder and schizophrenia

Attentional and executive impairments have been found both in patients with schizophrenia and in their unaffected first-degree relatives, suggesting that they might be considered as familial vulnerability markers. Several studies have shown that the performance of bipolar patients does not significantly differ from that of schizophrenic patients, so that executive and attentional deficits might not be specific to schizophrenia. In the present study, we aimed to identify executive dysfunctions in schizophrenia and bipolar disorder that might be vulnerability trait markers specific to one or common to both of these diseases. We assessed cognitive performance of euthymic bipolar and schizophrenic patients, their unaffected first-degree relatives and a healthy control group, using neuropsychological tasks to test different components of executive function: the Verbal Fluency Test, the Stroop Word Colour Test, the Wisconsin Card Sorting Test and the Trail Making Test. The two groups of patients and their unaffected relatives demonstrated disproportionately increased slowness on the Stroop test in comparison to the normal healthy group. Patients with schizophrenia performed poorly on all the tests in comparison to the normal healthy subjects, while no other impairment was observed in the bipolar patients and in the relatives of schizophrenic and bipolar patients. Enhanced susceptibility to interference and reduced inhibition could be transnosographical markers for a shared familial vulnerability common to schizophrenia and bipolar disorders.

Specific executive/attentional deficits in patients with schizophrenia or bipolar disorder who have a positive family history of psychosis

Neurocognitive impairments are well documented in patients with schizophrenia and their healthy first-degree biological relatives. Less is known about neuropsychological performance in bipolar disorders, but some studies indicate that, compared to schizophrenia, bipolar disorder displays a similar profile pattern with less severe deficits. The genetic and environmental contributions to the development of neurocognitive deficits are also unclear. This study explored the effect of a family history (FH) of psychotic disorders in first-degree relatives on a variety of cognitive domains (abstraction and flexibility, verbal fluency, verbal memory, motor activity and visual-motor processing/attention) in 30 patients with schizophrenia, and 24 type I bipolar patients. After adjusting the results for age, gender, education level and pre-morbid intelligence, patients with schizophrenia or bipolar disorder with positive FH (n=18) performed significantly worse than patients with negative FH (n=36) on the visual-motor processing/attention domain. These findings were independent of the specific diagnosis. Moreover, when logistic regression analysis was performed, poor Digit Symbol performance was the only predictor of belonging to the positive FH group. Our results are compatible with the existence of some common genetic factors between the illnesses, as well as the involvement of identical, or at least similar, disordered brain systems in both disorders. These findings are discussed within the context of the continuum model of psychosis.

Reconsidering the classification of schizophrenia and manic depressive illness--a critical analysis and new conceptual model

The idea of 'disease entity' in psychiatry and the nosologic map of insanity with the distinction between dementia praecox (schizophrenia since Bleuler 1911) and manic depressive insanity, originally developed by Emil Kraepelin (1986), is an important landmark in the history of psychiatry (Jablensky 1995). This classification, however, has been vigorously debated throughout the years, and new evidence emerging from epidemiological, clinical, genetic and biological research demonstrates that the two nosological categories have distinct features as well as share many similarities in their risk factors, genetic predisposition, brain pathology, neurophysiology, clinical phenomenology and response to treatment, thus raising questions about the validity of the categorical classification of psychoses. In this paper we examine some of the similarities and differences between schizophrenia and bipolar illness emerging from recent biological and clinical research and attempt to clarify major inherent logical contradictions in the application of the 'disease' model of psychiatric diagnosis to the categorical classification of schizophrenia and bipolar illness. Then we examine how similar predicaments have been resolved in other natural classification systems, namely the biological classification of species and the periodic table of the elements. Finally we propose a hypothetical conceptual approach to the classification of psychoses that has been greatly informed by the organizing principle underlying the periodic table of the elements, and is distinct from the 'disease' model of psychiatric classification.

Boundaries of schizophrenia

The frontiers of schizophrenia are being increasingly challenged from several directions. In addition to ongoing debate as to divisions between schizophrenia and disorders of the schizophrenic spectrum, including schizotypal personality disorder and schizophreniform disorder, it has been suggested that obsessive-compulsive disorder might overlap phenomenologically with schizophrenia. There has been a long debate around the relationship of schizophrenia to affective disorders, particularly bipolar and schizoaffective disorder. The evidence suggests that although schizotypal personality and schizophreniform disorders are not homogeneous syndromes, they are related to or represent milder forms of schizophrenia. Obsessive-compulsive disorder seems to involve pathology in many of the same regions as observed in some patients with schizophrenia, which may account for the significant incidence of obsessive-compulsive symptoms in a subset of patients with schizophrenia. Despite similarities between schizophrenia and bipolar disorder, significant differences extend across suggested causes, phenomenology, and pathophysiology. These findings support the current conceptualization that the two disorders represent distinct disorders, probably with heterogeneous causes, rather than the ends of a spectrum of symptoms comprising a single syndrome. Schizoaffective disorder likely is made up of patients from the schizophrenic and bipolar cluster of illnesses. The long-standing debate as to the boundaries of schizophrenia is ultimately must await the eventual further elaboration of the underlying causes of schizophrenia and other psychotic disorders.

Schizophrenia and bipolar disorder are distinguished mainly by differences in neurodevelopment

This paper examines the commonalities and the differences between schizophrenia and bipolar disorder. Recent studies suggest a possible overlap in genetic susceptibility to the two conditions. However, while the influence of early environmental effects, particularly obstetric complications, has been established for schizophrenia, no such replicable association with bipolar disorder has been found. Structural abnormalities of the brain have been identified in both schizophrenia and bipolar disorder, but while the volume of the amygdala and hippocampus appears decreased in schizophrenia, this is not the case in bipolar disorder; indeed there are some suggestions of increased volume of the amygdala. Furthermore, schizophrenia is characterised by lower IQ, executive function and verbal memory, but there is little evidence of trait neuropsychological deficits in bipolar disorder. Similarly, premanic children do not show the cognitive and neuromotor impairments characteristic of those destined to develop schizophrenia. The most plausible explanation is that the two conditions share some genetic predisposition but differ in that schizophrenia but not bipolar disorder is subject to additional genes or early environmental hazards causing neurodevelopmental impairment.

PANSS factors and scores in schizophrenic and bipolar disorders during an index acute episode: a further analysis of the cognitive component

To investigate the factor structure of psychotic symptoms, we compared the clinical characteristics of manic patients with those of schizophrenic patients evaluated with positive and negative syndrome scale (PANSS). The clinical symptoms of 148 bipolar patients and 86 schizophrenic patients hospitalized for an index psychotic episode were assessed. Schizophrenic patients showed more positive and cognitive symptoms than bipolars. The factor analysis of the two PANSS scores showed a three-factor solution with 'positive', 'negative' and 'mixed' depressive-activated factors for bipolars and 'positive', 'negative' and 'depressive' factors for schizophrenics. In both groups, the 'cognitive cluster' loaded on the first 'positive' factor while the 'lack of insight' (LOI) has a different meaning in the two groups, more related to the positive symptoms in the bipolar patients and more related to the negative symptoms in the schizophrenic patients. This finding suggests that LOI could be a non-unitary phenomenon in psychoses and it should be further explored to better elucidate differences in symptom structures between schizophrenic and bipolar disorders.

Sustained attention deficit in bipolar disorder

BACKGROUND

Recovery in bipolar disorder is central to its definition but is rarely complete. Previous work has suggested that neuropsychological impairment persists during the euthymic state but has been confounded partly by mild affective symptoms in remitted patients.

AIMS

To characterise neuropsychological functioning in the euthymic phase of bipolar disorder with an emphasis on tasks of executive functioning.

METHOD

Thirty euthymic patients with bipolar disorder were compared with thirty healthy controls on neuropsychological tasks differentially sensitive to damage within prefrontal cortex.

RESULTS

Bipolar I patients were impaired on tasks of attentional set shifting, verbal memory and sustained attention. Only sustained attention deficit survived controlling for mild affective symptoms. This deficit was related to progression of illness, but was none the less present in a subgroup of patients near illness onset.

CONCLUSIONS

Sustained attention deficit may represent a neuropsychological vulnerability marker for bipolar disorder, providing a focus for further understanding of the phenotype and analysis of the neuronal networks involved.

Is it time to develop a new cognitive therapy for psychosis--cognitive remediation therapy (CRT)?

The cognitive difficulties associated with the disorder of schizophrenia seem to be predictive of future dependence on psychiatric services and predict social functioning. Cognitive remediation therapy (CRT) was designed to rehabilitate these cognitive functions, and the interest in it has grown dramatically over the past ten years. However, the programmes are rarely based on clear theoretical principles and sometimes rely heavily on practice rather than guided learning. The evidence for their efficacy is variable and seems to be dependent on the use of specific components of training. The current review tries to put this evidence into context and sets out a programme of research, which is essential in this area if future progress is to be made.

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.

Working memory in schizophrenia and mania: correlation with symptoms during the acute and subacute phases

OBJECTIVE

The aims of this study were to examine working memory in the acute subacute phase of schizophrenia and mania and to examine correlations between working memory and specific symptom domains.

METHOD

Visuospatial working memory and symptom profiles were assessed in three groups (schizophrenia group, n= 19; mania, n= 12; controls, n= 19) on two occasions separated by 4 weeks.

RESULTS

Both patient groups had significant deficits on working memory compared to the well controls and the schizophrenia and mania groups were equally impaired. All groups showed equivalent improvement over time. In the patient groups, impaired working memory was significantly correlated with the presence of both negative symptoms and positive thought disorder.

CONCLUSION

Impaired working memory is found in both schizophrenia and mania during the acute subacute phases. Further research is required in order to clarify the neurocognitive mechanisms linking impaired working memory with both negative symptoms and positive thought disorder.

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.