Neuropsychological performance of monozygotic twins discordant for bipolar disorder

Clinical neuropsychological characteristics of bipolar disorder, with a focus on cognitive and linguistic pattern: a conceptual analysis

Neuropsychology is an academic discipline that investigates the intricate interplay between the brain, mind, and behavior. It accomplishes this by examining the underlying structure and activities of the brain, with a particular focus on psychological phenomena such as language, motivation, memory, attention, thinking, consciousness, learning, and efficacy. The assessment of neuropsychological changes in individuals diagnosed with bipolar disorder has received limited attention in comparison to other psychiatric conditions, such as schizophrenia, for instance. Nevertheless, there has been a growing interest in the etiological implications, therapies, preventions, and prognostic factors related to social competence and the quality of life of patients. The objective of this review is to compile and analyze the existing research conducted thus far on the association between cognitive abnormalities and bipolar disorder. This study has examined research conducted across many stages of the condition, including depression and mania. Additionally, it has explored comparative studies involving people with schizophrenia, as well as the potential impact of psychopharmaceutical interventions.

Evaluating cognitive function in unaffected relatives of individuals with bipolar disorders: A meta-analysis

BACKGROUND

Available studies have evaluated cognition in the unaffected relatives of bipolar disorder patients; however, to our knowledge, there has been no quantitative analysis evaluating the foregoing association. Herein, this meta-analysis aims to provide a quantitative synthesis of the extant literature reporting on the association between performance in cognitive domains (i.e., executive function, attention, learning and memory or global cognition) amongst unaffected individuals of probands with bipolar disorders.

METHODS

Online databases (i.e., PubMed, PsycINFO) and Google Scholar were searched from inception to 20 September 2021. Studies with unaffected, first-degree relatives of individuals with DSM-IV or DSM-5 defined bipolar disorders were included. The risk of bias was assessed using the ROBINS-1 tool, and the quality of the sources was evaluated using GRADE criteria. The results of the studies were quantitatively synthesized using Cohen's d effect sizes via a random-effects meta-analytic approach on JASP.

RESULTS

A total of 15 studies were included in the final review. Overall, results indicate that cognitive performance across all domains is moderately impaired in unaffected relatives of individuals with bipolar disorders (d = 0.488). Sub-analysis suggests there is a higher level of impairment in executive functioning (d = 0.612).

DISCUSSION

The identification of cognitive deficits in unaffected relatives of probands with bipolar disorders indicates that cognitive impairment is endophenotypic and a core disturbance in persons with bipolar disorders; future studies should endeavour to target cognition as a potential pre-emptive and prevention strategy of bipolar disorders.

Deficits in generalized cognitive ability, visual sensorimotor function, and inhibitory control represent discrete domains of neurobehavioral deficit in psychotic disorders

Psychotic disorders are characterized by impaired cognition, yet some reports indicate specific deficits extend beyond reduced general cognitive ability. This study utilized exploratory and confirmatory factor analytic methods to evaluate the latent structure of a broad neurocognitive battery used in the Bipolar-Schizophrenia Network of Intermediate Phenotypes (B-SNIP) study, which included neuropsychological and neurophysiological measures in psychotic disorder probands and their unaffected first-degree relatives. Findings indicate that the factor structure of data from this set of assessments is more complex than the unitary factor of global cognitive ability underlying the Brief Assessment of Cognition in Schizophrenia (BACS). In addition to assessing generalized cognitive ability, two other factors were identified: visual sensorimotor function and inhibitory behavioral control. This complex cognitive architecture, derived in controls, generalized to patients across the psychosis spectrum and to their unaffected relatives. These findings highlight the need for a more differentiated assessment of neurobehavioral functions in studies designed to test for diagnostically specific biomarkers, endophenotypes for gene discovery and beneficial effects of therapeutics on cognitive function.

Evaluating endophenotypes for bipolar disorder

BACKGROUND

Phenotypic heterogeneity is a major impediment to the elucidation of the neurobiology and genetics of bipolar disorder. Endophenotype could help in reducing heterogeneity by defining biological traits that are more direct expressions of gene effects. The aim of this review is to examine the recent literature on clinical, epidemiological, neurobiological, and genetic findings and to select and evaluate candidate endophenotypes for bipolar disorder. Evaluating putative endophenotype could be helpful in better understanding the neurobiology of bipolar disorder by improving the definition of bipolar-related phenotypes in genetic studies. In this manner, research on endophenotypes could be useful to improve psychopathological diagnostics in the long-run by dissecting psychiatric macro phenotypes into biologically valid components.

MAIN BODY

The associations among the psychopathological and biological endophenotypes are discussed with respect to specificity, temporal stability, heritability, familiarity, and clinical and biological plausibility. Numerous findings regarding brain function, brain structure, neuropsychology and altered neurochemical pathways in patients with bipolar disorder and their relatives deserve further investigation. Overall, major findings suggest a developmental origin of this disorder as all the candidate endophenotypes that we have been able to select are present both in the early stages of the disorder as well as in subjects at risk.

CONCLUSIONS

Among the stronger candidate endophenotypes, we suggest circadian rhythm instability, dysmodulation of emotion and reward, altered neuroimmune state, attention and executive dysfunctions, anterior cingulate cortex thickness and early white matter abnormalities. In particular, early white matter abnormalities could be the result of a vulnerable brain on which new stressors are added in young adulthood which favours the onset of the disorder. Possible pathways that lead to a vulnerable brain are discussed starting from the data about molecular and imaging endophenotypes of bipolar disorder.

Is aberrant affective cognition an endophenotype for affective disorders? - A monozygotic twin study

BACKGROUND

Identification of endophenotypes can improve prevention, detection and development of new treatments. We therefore investigated whether aberrant affective cognition constitutes an endophenotype for affective disorders by being present in monozygotic (MZ) twins with unipolar or bipolar disorder in partial remission (i.e. affected) and their unaffected co-twins (i.e. high-risk) relative to twins with no family history of affective disorder (i.e. low-risk).

METHODS

We conducted an assessor blind cross-sectional study from 2014 to 2017 of MZ twins using Danish population-based registers in recruitment. Twins attended one test session involving neurocognitive testing, clinical ratings and questionnaires. Main outcomes were attention to and recognition of emotional facial expressions, the memory of emotional self-referential words, emotion regulation and coping strategies.

RESULTS

Participants were 103 affected, 44 high-risk and 36 low-risk MZ twins. Groups were demographically well-balanced and showed comparable non-affective cognitive performance. We observed no aberrant affective cognition in affected and high-risk relative to low-risk twins. However, high-risk twins displayed attentional avoidance of emotional faces (ps ⩽ 0.009) and more use of task-oriented coping strategies (p = 0.01) compared with affected twins. In contrast did affected twins show more emotion-oriented coping than high- and low-risk twins (ps ⩽ 0.004).

CONCLUSIONS

Our findings provide no support of aberrant affective cognition as an endophenotype for affective disorders. High-risk twins' attentional avoidance of emotional faces and greater use of task-oriented coping strategies may reflect compensatory mechanisms.

Resting regional brain activity correlates of verbal learning deficit in major depressive disorder

Memory deficits are reported in major depressive disorder (MDD). Prefrontal cortical and mesiotemporal cortical (MTC)/subcortical regions are involved in the Buschke Selective Reminding Task (SRT), a verbal list-learning task. To determine whether depression-related changes in resting brain metabolism explain (in part) the deficits in SRT performance found in MDD, statistical correlation maps were calculated between SRT total recall score (TR) and relative regional cerebral metabolic rate for glucose (rCMRglu), measured by [¹⁸F]-flourodeoxyglucose (FDG) positron emission tomography (PET), in unmedicated, depressed MDD patients (N = 29). Subsequently, to explore hypothesized loss of top-down control in MDD, we compared the correlations between rCMRglu of SRT-relevant regions of the dorsolateral prefrontal cortex (dlPFC) and amygdala in a larger cohort of MDD (N = 60; 29 inclusive) versus healthy controls (HC) (N = 43). SRT performance of patients is on average 0.5 standard deviation below published normative mean. TR and rCMRglu positively correlate in bilateral dorsomedial PFC, dlPFC, dorsal anterior cingulate; negatively correlate in bilateral MTC/subcortical regions, and cerebellum. rCMRglu in dlPFC correlates negatively with that in amygdala in HC but not in MDD. Depression-related changes present in FDG-PET measured resting brain activity may be in part responsible for memory deficit found in MDD.

Cognitive abilities in first-degree relatives of individuals with bipolar disorder

BACKGROUND

Although the study of cognition in first degree relatives (FDRs) is not new, findings in this group are still somewhat inconsistent and much of the research examining FDR populations include individuals under the age of 25, who are arguably still at significant risk to go on to develop BD. The present study aimed to establish the value of cognitive performance as a genuine endophenotypic marker of familial risk for bipolar disorder (BD), by examining cognition in FDRs aged 25 years or older.

METHODS

The current study compared the cognitive performance of 27 unaffected FDRs to 47 healthy controls (HCs) and 28 BD patients using the MATRICS Consensus Cognitive Battery (MCCB).

RESULTS

Results indicated that FDRs had impaired verbal learning performance, as well as selective impairments on a measure of speed of processing; and a measure of spatial working memory compared to HC.

LIMITATIONS

Limitations relate to the potential insensitivity of some of the tests in the MCCB for detecting cognitive deficits that have been previously noted in BD and FDR samples using other batteries.

CONCLUSIONS

Findings from this study implicate verbal learning, processing speed and working memory performance as promising candidate endophenotypes of familial risk for BD.

Prediction of vulnerability to bipolar disorder using multivariate neurocognitive patterns: a pilot study

Bipolar disorder (BD) is a common disorder with high reoccurrence rate in general population. It is critical to have objective biomarkers to identify BD patients at an individual level. Neurocognitive signatures including affective Go/No-go task and Cambridge Gambling task showed the potential to distinguish BD patients from health controls as well as identify individual siblings of BD patients. Moreover, these neurocognitive signatures showed the ability to be replicated at two independent cohorts which indicates the possibility for generalization. Future studies will examine the possibility of combining neurocognitive data with other biological data to develop more accurate signatures.

Differences in cognitive deficits in individuals with subthreshold syndromes with and without family history of bipolar disorder

Little is known about the development of cognitive deficits prior to the official onset of bipolar disorder (BP). The aim of this study was to investigate neurocognitive performance in two early stages of BP. This high-risk design study recruited a group of offspring of parents with BP (n = 58), aged 8-28 years. Based on the subthreshold syndromes, the "unaffected" offspring were further divided into high-risk (HR) and ultra-high-risk (UHR) stages. For comparison, a group of individuals with subthreshold symptoms but without family history of psychiatric disorder (n = 17) and 48 healthy controls (HCs) were included. The MATRICS Consensus Cognitive Battery (MCCB) and Tower of London task were applied to assess neuropsychological performance. The HR offspring performed significantly poorer on verbal learning and memory when compared with HCs, indicating that the deficits may serve as neurocognitive endophenotypes for BP. Deficits in working memory, visual-spatial memory, and cognitive planning were observed in the UHR offspring when compared with HCs, suggestive of risk of developing BP. The deficits observed in the UHR offspring were absent in the individuals with subthreshold symptoms without psychiatric family history. Our data suggest that cognitive deficits become apparent prior to the official onset of BP, with specific deficits observable in different early stages. These results nonetheless are based on small sample size and a cross-sectional design. Given this and the heterogeneity of bipolar disorders, these findings should be interpreted cautiously and require replication.

The management of cognitive impairment in bipolar disorder: current status and perspectives

Bipolar disorder (BD) is associated with important cognitive deficits that persist during the periods of remission. Although these deficits seem to play an important role in the functional impairment experienced by bipolar patients, evidence regarding their clinical management is scant. We revised the databases PubMed, MEDLINE, and clinicaltrials.gov, searching for studies focusing on the pharmacological and nonpharmacological treatment of cognitive deficits among bipolar patients. In addition, a manual search of bibliographical cross-references was performed. Currently, there is no Food and Drug Administration-approved pharmacological agent for the management of cognitive deficits in BD. A number of agents have been tested in the treatment of cognitive deficits in BD, with mixed results. Nonpharmacological interventions, such as cognitive remediation and noninvasive brain stimulation techniques, seem promising, but their role has not yet been properly explored among bipolar patients. Additional studies, aiming at evaluating the efficacy of interventions combining cognitive rehabilitation and biological treatments, are highly desirable.

A Patient With Bipolar Illness and Her Neuropsychological Signature

This article describes a case study in which neuropsychological assessment was carried out on a 30-year-old, previously diagnosed, bipolar female to determine existence of specific deficits in cognitive function. The patient, whose mood cycles were 12 hours to 24 hours, was subsequently evaluated 8 hours per day for 5 consecutive days (a complete work week of neuropsychological assessment). Neuropsychological results showed motor slowing, right hemispheric dysfunctioning, and memory problems during depressive periods and attentional and executive problems during hypomanic and manic periods. The most normal performance was found during euthymic periods. In addition, left and right hemi visual neglect, aphasia, and sensorimotor problems were present across all mood states. Treatment implications are subsequently described.

Cognitive deficits in first-degree relatives of bipolar patients: the use of homogeneous subgroups in the search of cognitive endophenotypes

Previous studies have demonstrated impairments in attention, memory and executive functions in euthymic bipolar patients (BP) as well as their unaffected first-degree relatives, albeit in an attenuated form. Subsequently, cognitive deficits are discussed as a possible endophenotype of bipolar disorder. However, recent studies showed that only a subgroup of BP shows cognitive impairments. The aim of the present study was to investigate cognitive functioning in relatives compared to BP, to find out if the differentiation in a cognitive deficit vs. non-deficit subgroup is valid for relatives of BP, too. Therefore, the performance of 27 unaffected relatives of BP, 27 euthymic BP and 27 HC were compared using a neuropsychological test battery. The results showed that BP exhibited a reduced psychomotor speed and deficits in working memory compared to relatives and HC. Relatives performed significantly slower (psychomotor speed) as compared to HC (p = 0.024); performance in the other test measures lie between BP and HC. Furthermore, a detailed evaluation of the data indicated that only subgroups of BP and relatives exhibited cognitive impairments in the implemented tests. However, the deficit and non-deficit groups did not differ in sociodemographic and clinical variables from each other, possibly due to the small sample size. In conclusion, our results suggest that reduced psychomotor speed could serve as a potential endophenotype for bipolar disorder which should be investigated along the developmental trajectory of this disorder, also to examine whether abnormalities therein precede onset of the first mood episode. Furthermore, the division of relatives into subgroups aids in the identification of stable trait markers and high-risk bipolar groups and could enable early prevention strategies. As to that more research using distinct and homogeneous subgroups is necessary.

New insights into the endophenotypic status of cognition in bipolar disorder: genetic modelling study of twins and siblings

BACKGROUND

Twin studies have lacked statistical power to apply advanced genetic modelling techniques to the search for cognitive endophenotypes for bipolar disorder.

AIMS

To quantify the shared genetic variability between bipolar disorder and cognitive measures.

METHOD

Structural equation modelling was performed on cognitive data collected from 331 twins/siblings of varying genetic relatedness, disease status and concordance for bipolar disorder.

RESULTS

Using a parsimonious AE model, verbal episodic and spatial working memory showed statistically significant genetic correlations with bipolar disorder (rg = |0.23|-|0.27|), which lost statistical significance after covarying for affective symptoms. Using an ACE model, IQ and visual-spatial learning showed statistically significant genetic correlations with bipolar disorder (rg = |0.51|-|1.00|), which remained significant after covarying for affective symptoms.

CONCLUSIONS

Verbal episodic and spatial working memory capture a modest fraction of the bipolar diathesis. IQ and visual-spatial learning may tap into genetic substrates of non-affective symptomatology in bipolar disorder.

Neuropsychological and social cognitive function in young people at genetic risk of bipolar disorder

BACKGROUND

Impairments in key neuropsychological domains (e.g. working memory, attention) and social cognitive deficits have been implicated as intermediate (endo) phenotypes for bipolar disorder (BD), and should therefore be evident in unaffected relatives.

METHOD

Neurocognitive and social cognitive ability was examined in 99 young people (age range 16-30 years) with a biological parent or sibling diagnosed with the disorder [thus deemed to be at risk (AR) of developing BD], compared with 78 healthy control (HC) subjects, and 52 people with a confirmed diagnosis of BD.

RESULTS

Only verbal intelligence and affective response inhibition were significantly impaired in AR relative to HC participants; the BD participants showed significant deficits in attention tasks compared with HCs. Neither AR nor BD patients showed impairments in general intellectual ability, working memory, visuospatial or language ability, relative to HC participants. Analysis of BD-I and BD-II cases separately revealed deficits in attention and immediate memory in BD-I patients (only), relative to HCs. Only the BD (but not AR) participants showed impaired emotion recognition, relative to HCs.

CONCLUSIONS

Selective cognitive deficits in the capacity to inhibit negative affective information, and general verbal ability may be intermediate markers of risk for BD; however, the extent and severity of impairment in this sample was less pronounced than has been reported in previous studies of older family members and BD cases. These findings highlight distinctions in the cognitive profiles of AR and BD participants, and provide limited support for progressive cognitive decline in association with illness development in BD.

Neurodevelopmental origins of bipolar disorder: iPSC models

Bipolar disorder (BP) is a chronic neuropsychiatric condition characterized by pathological fluctuations in mood from mania to depression. Adoption, twin and family studies have consistently identified a significant hereditary component to BP, yet there is no clear genetic event or consistent neuropathology. BP has been suggested to have a developmental origin, although this hypothesis has been difficult to test since there are no viable neurons or glial cells to analyze, and research has relied largely on postmortem brain, behavioral and imaging studies, or has examined proxy tissues including saliva, olfactory epithelium and blood cells. Neurodevelopmental factors, particularly pathways related to nervous system development, cell migration, extracellular matrix, H3K4 methylation, and calcium signaling have been identified in large gene expression and GWAS studies as altered in BP. Recent advances in stem cell biology, particularly the ability to reprogram adult somatic tissues to a pluripotent state, now make it possible to interrogate these pathways in viable cell models. A number of induced pluripotent stem cell (iPSC) lines from BP patient and healthy control (C) individuals have been derived in several laboratories, and their ability to form cortical neurons examined. Early studies suggest differences in activity, calcium signaling, blocks to neuronal differentiation, and changes in neuronal, and possibly glial, lineage specification. Initial observations suggest that differentiation of BP patient-derived neurons to dorsal telencephalic derivatives may be impaired, possibly due to alterations in WNT, Hedgehog or Nodal pathway signaling. These investigations strongly support a developmental contribution to BP and identify novel pathways, mechanisms and opportunities for improved treatments.

Executive function in parents of patients with familial versus sporadic bipolar disorder

OBJECTIVE

Studies investigating the cognitive function of healthy relatives of patients with bipolar disorder are conflicting, and the neurocognitive profile of relatives of bipolar disorder probands is still unclear. We aimed to evaluate executive function in unaffected parents of familial and sporadic patients with bipolar disorder.

METHODS

The study included 24 unaffected familial parents (FP) of patients with bipolar disorder, 26 unaffected sporadic parents (SP) of patients with bipolar disorder and 26 controls matched with the parents for gender, age and duration of education (76 subjects in total). All of the subjects were interviewed with the Structured Clinical Interview for DSM-IV-Axis I. Executive function was assessed using the California Verbal Learning Test (CVLT), the Trail Making Test (TMT), the Wisconsin Card Sorting Test (WCST) and the Stroop test.

RESULTS

In comparison to their respective matched controls, FP performed significantly worse on the CVLT, TMT, WCST and Stroop test, whereas SP performed significantly worse only on WCST perseverative errors and Stroop color test. FP performed significantly worse than SP on the CVLT, TMT, and WCST.

CONCLUSION

The present study investigated relatives with and without a family history of bipolar disorder separately and found that executive function was impaired in parents with a positive family history of bipolar disorder. These findings bring more evidence suggesting that deficits in prefrontal executive function and verbal memory are associated with familial vulnerability to bipolar disorder and that executive function and verbal memory impairments may represent a potential endophenotype of bipolar disorder.

Regressing to Prior Response Preference After Set Switching Implicates Striatal Dysfunction Across Psychotic Disorders: Findings From the B-SNIP Study

Difficulty switching behavioral response sets is established in psychotic disorders. In rodent models, prefrontal lesions cause difficulty initially switching to new response sets (perseverative errors) while striatal lesions cause difficulty suppressing responses to previous choice preferences (regressive errors). Studies of psychotic disorders have not previously assessed these 2 error types. Bipolar and Schizophrenia Network on Intermediate Phenotypes (B-SNIP) participants included probands with schizophrenia (N = 212), psychotic bipolar (N = 192), and schizoaffective disorder (N = 131), their first-degree relatives (N = 267,226,165 respectively), and healthy controls (N = 258). Participants completed the Penn Conditional Exclusion Test (PCET) to assess cognitive set switching and the Brief Assessment of Cognition in Schizophrenia (BACS) to assess generalized neuropsychological dysfunction. All proband groups displayed elevated rates of perseverative and regressive errors compared to controls. After correcting for generalized cognitive deficits to identify specific deficits in set shifting and maintenance, there were no significant group differences for perseverative errors, while the increased rate of regressive errors remained significant. Level of regressive errors was similar across proband groups with minimal correlations with antipsychotic medication dose, clinical ratings, and demographic characteristics. Relatives of schizophrenia patients showed increased rates of regressive errors, but familiality of this trait was significant only in bipolar pedigrees. Regressive errors were partially independent of generalized cognitive deficits, suggesting a potentially informative and specific cognitive deficit across psychotic disorders. Preclinical data indicate that this deficit could be related to altered function in a neural system that may include the dorsal striatum or other elements of frontostriatal systems.

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.

Advancing biomarker research: utilizing 'Big Data' approaches for the characterization and prevention of bipolar disorder

OBJECTIVE

To provide a strategic framework for the prevention of bipolar disorder (BD) that incorporates a 'Big Data' approach to risk assessment for BD.

METHODS

Computerized databases (e.g., Pubmed, PsychInfo, and MedlinePlus) were used to access English-language articles published between 1966 and 2012 with the search terms bipolar disorder, prodrome, 'Big Data', and biomarkers cross-referenced with genomics/genetics, transcriptomics, proteomics, metabolomics, inflammation, oxidative stress, neurotrophic factors, cytokines, cognition, neurocognition, and neuroimaging. Papers were selected from the initial search if the primary outcome(s) of interest was (were) categorized in any of the following domains: (i) 'omics' (e.g., genomics), (ii) molecular, (iii) neuroimaging, and (iv) neurocognitive.

RESULTS

The current strategic approach to identifying individuals at risk for BD, with an emphasis on phenotypic information and family history, has insufficient predictive validity and is clinically inadequate. The heterogeneous clinical presentation of BD, as well as its pathoetiological complexity, suggests that it is unlikely that a single biomarker (or an exclusive biomarker approach) will sufficiently augment currently inadequate phenotypic-centric prediction models. We propose a 'Big Data'- bioinformatics approach that integrates vast and complex phenotypic, anamnestic, behavioral, family, and personal 'omics' profiling. Bioinformatic processing approaches, utilizing cloud- and grid-enabled computing, are now capable of analyzing data on the order of tera-, peta-, and exabytes, providing hitherto unheard of opportunities to fundamentally revolutionize how psychiatric disorders are predicted, prevented, and treated. High-throughput networks dedicated to research on, and the treatment of, BD, integrating both adult and younger populations, will be essential to sufficiently enroll adequate samples of individuals across the neurodevelopmental trajectory in studies to enable the characterization and prevention of this heterogeneous disorder.

CONCLUSIONS

Advances in bioinformatics using a 'Big Data' approach provide an opportunity for novel insights regarding the pathoetiology of BD. The coordinated integration of research centers, inclusive of mixed-age populations, is a promising strategic direction for advancing this line of neuropsychiatric research.

Impact of depressive episodes on cognitive deficits in early bipolar disorder: data from the Systematic Treatment Optimization Programme for Early Mania (STOP-EM)

BACKGROUND

Although manic episodes reportedly contribute to cognitive deficits in bipolar I disorder, the contribution of depressive episodes is poorly researched.

AIMS

We investigated the impact of depressive episodes on cognitive function early in the course of bipolar I disorder.

METHOD

A total of 68 patients and 38 controls from the Systematic Treatment Optimization Programme for Early Mania (STOP-EM) first-episode mania programme were examined. We conducted (a) a cross-sectional analysis of the impact of prior depressive episodes on baseline cognitive function and (b) a prospective analysis assessing the contribution of depression recurrence within 1 year following a first episode of mania on cognitive functioning.

RESULTS

The cross-sectional analysis showed no significant differences between patients with past depressive episodes compared with those without, on overall or individual domains of cognitive function (all P>0.09). The prospective analysis failed to reveal a significant group×time interaction for cognitive decline from baseline to 1 year (P = 0.99) in patients with a recurrence of depressive episodes compared with those with no recurrence. However, impaired verbal memory at baseline was associated with a depression recurrence within 1 year.

CONCLUSIONS

Although deficits in all domains of cognitive function are seen in patients early in the course of bipolar disorder, depressive episodes do not confer additional burden on cognitive function. However, poorer verbal memory may serve as a marker for increased susceptibility to depression recurrence early in the course of illness.

Discordant twins as a tool to unravel the aetiology of bipolar disorder

This editorial focuses on discordant twins as a valuable epidemiological design for psychiatric aetiological research. First, we summarise the advantages and strengths of this design over the classical matched case-control study. Then, we draw attention to the use of this method in bipolar disorder, revising previous discordant-twin studies. A future greater use of discordant twins is desirable to gain further relevant insights in the aetiology of bipolar disorder.

Neuropsychological deficits in bipolar depression persist after successful antidepressant treatment

BACKGROUND

Bipolar disorder is a common disabling illness with a lifetime morbid risk of approximately 4%. Neuropsychological deficits constitute enduring trait-like features in bipolar disorder, are associated with each phase of the illness and persist also in euthymia. Total sleep deprivation (TSD) has been shown to cause rapid and sustained antidepressant effects in bipolar depression and to revert the biased self description and speed of information processing present in these patients. The aim of the study was to assess neuropsychological performances first in a sample of bipolar patients during a depressive episode compared to healthy controls and secondly to investigate if TSD treatment would change cognitive performances.

METHODS

One-hundred bipolar patients and 100 healthy controls were evaluated through the Brief Assessment of Cognition in Schizophrenia, 42 patients were assessed before and after TSD treatment.

RESULTS

Bipolar patients obtained significantly lower domain scores across the entire battery compared to healthy subjects. Cognitive deficits persisted in each function despite a clinical improvement of depressive symptomatology.

LIMITATIONS

Limitations of the study include issues such as generalizability, possible undetected past comorbidities, population stratification and ongoing medication.

CONCLUSIONS

This is the first study of the effect of TSD treatment on cognitive performance. TSD treatment improved clinical symptoms but not cognitive deficits however bipolar patients did not experience the well known worsening of performance observed in healthy controls after sleep loss.

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.

Ventral prefrontal executive function impairment as a potential endophenotypic marker for bipolar disorder

BACKGROUND

Patients with remitted bipolar disorder have cognitive impairments, particularly in executive functions. However, the findings of studies that investigated cognitive functions in unaffected relatives of patients with bipolar disorder are conflicting.

AIMS

The aim of this study is to investigate executive functions in healthy parents of patients with bipolar I disorder, along with bipolar I disorder patients and matched controls. It has been hypothesized that both patients with bipolar I disorder and their parents would have executive function impairments compared with controls.

METHODS

25 patients with bipolar I disorder, in full remission, 25 healthy controls that matched the patients with respect to age, gender and education, 50 healthy parents of those patients and 50 healthy controls that matched the parents for age, gender and education were included in the study. All the participants were interviewed with Structured Clinical Interview for DSM-IV-Axis I (SCID-I). Executive functions were assessed using the Verbal Fluency Test (VFT), Trail Making Test (TMT), Wisconsin Card Sorting Test (WCST) and Stroop Test.

RESULTS

Patients performed significantly worse than their matched controls on the VFT, TMT and Stroop tests, but not on the WCST. Parents performed significantly worse than their matched controls on the TMT and Stroop tests, but not on the VFT and WCST.

CONCLUSIONS

Our results bring more evidence that deficits in ventral, but not dorsal prefrontal executive functions are associated with familial vulnerability to bipolar disorder and ventral prefrontal executive function impairments may represent a potential endophenotype for bipolar disorder.

Neuropsychological impairments in schizophrenia and psychotic bipolar disorder: findings from the Bipolar-Schizophrenia Network on Intermediate Phenotypes (B-SNIP) study

OBJECTIVE

Familial neuropsychological deficits are well established in schizophrenia but remain less well characterized in other psychotic disorders. This study from the Bipolar-Schizophrenia Network on Intermediate Phenotypes (B-SNIP) consortium 1) compares cognitive impairment in schizophrenia and bipolar disorder with psychosis, 2) tests a continuum model of cognitive dysfunction in psychotic disorders, 3) reports familiality of cognitive impairments across psychotic disorders, and 4) evaluates cognitive impairment among nonpsychotic relatives with and without cluster A personality traits.

METHOD

Participants included probands with schizophrenia (N=293), psychotic bipolar disorder (N=227), schizoaffective disorder (manic, N=110; depressed, N=55), their first-degree relatives (N=316, N=259, N=133, and N=64, respectively), and healthy comparison subjects (N=295). All participants completed the Brief Assessment of Cognition in Schizophrenia (BACS) neuropsychological battery.

RESULTS

Cognitive impairments among psychotic probands, compared to healthy comparison subjects, were progressively greater from bipolar disorder (z=-0.77) to schizoaffective disorder (manic z=-1.08; depressed z=-1.25) to schizophrenia (z=-1.42). Profiles across subtests of the BACS were similar across disorders. Familiality of deficits was significant and comparable in schizophrenia and bipolar disorder. Of particular interest were similar levels of neuropsychological deficits in relatives with elevated cluster A personality traits across proband diagnoses. Nonpsychotic relatives of schizophrenia probands without these personality traits exhibited significant cognitive impairments, while relatives of bipolar probands did not.

CONCLUSIONS

Robust cognitive deficits are present and familial in schizophrenia and psychotic bipolar disorder. Severity of cognitive impairments across psychotic disorders was consistent with a continuum model, in which more prominent affective features and less enduring psychosis were associated with less cognitive impairment. Cognitive dysfunction in first-degree relatives is more closely related to psychosis-spectrum personality disorder traits in psychotic bipolar disorder than in schizophrenia.

Increased risk of developing dementia in patients with bipolar disorder: a nested matched case-control study

OBJECTIVE

The association between bipolar disorder and subsequent dementia risk is not well established. The objective of this study was to investigate whether patients with bipolar disorder were at an increased risk for developing dementia.

METHODS

A conditional logistic regression model was performed using data from the National Health Insurance Research Database, a nationwide dataset in Taiwan. The study sample included 9,304 patients with incident dementia first diagnosed between 2000 and 2009, and 55,500 gender-, age-, and index date-matched subjects without dementia. Cerebrovascular disease, diabetes, hypertension, head injury, chronic pulmonary disease, alcohol-related disorders, substance use disorders, and health system utilization were treated as covariates in the analyses.

RESULTS

After controlling for the covariates, bipolar disorder was significantly associated with an increased risk of subsequent dementia [adjusted odds ratio (aOR) = 4.32, 95% confidence interval (CI): 3.21-5.82]. An increased risk of developing dementia was observed in males and females alike (aOR = 4.01, 95% CI: 2.53-6.35 in males; aOR = 4.55, 95% CI: 3.07-6.73 in females). Moreover, a significantly increased risk was observed in subjects diagnosed with dementia before the age of 65 years (aOR = 3.77, 95% CI: 1.78-8.01).

CONCLUSIONS

Findings from this study suggest a positive association between the presence of a lifetime history of bipolar disorder and an increased risk of developing dementia. Furthermore, our results also suggest that subjects with bipolar disorder tend to develop dementia in middle age. Going forward, it will be of importance to confirm our findings in different populations.

Psychological factors that may confer risk for bipolar disorder

Several psychological domains may be dysfunctional in people with bipolar disorder (BD). When dysfunction occurs prior to onset of mood symptoms, it may signify risk for onset of the full syndrome of illness. Among these domains, cognitive dysfunction has received considerable attention as a possible endophenotype for BD, with some suggestion that changes in cognitive function may antedate onset of mood symptoms in individuals at risk for BD. Domains of social cognition, including emotion comprehension, theory of mind, and empathy, along with autobiographical memory, represent understudied aspects of psychological function that may be dysfunctional in people with BD. Temperament and personality factors, such as ruminative tendencies and neuroticism, may also leave some people vulnerable to mood instability. This review summarises the evidence for dysfunction in each of these domains for people with BD and examines whether there is any evidence that this dysfunction antedates the onset of mood symptoms or confers risk for illness.

A review of cognitive neuropsychiatry in the taxonomy of eating disorders: state, trait, or genetic?

A greater understanding of neuropsychological traits in eating disorders may help to construct a more biologically based taxonomy. The aim of this paper is to review the current evidence base of neuropsychological traits in people with eating disorders. Evidence of difficulties in set shifting, weak central coherence, emotional processing difficulties, and altered reward sensitivity is presented for people both in the acute and recovered phase of the illness. These traits are also seen in first degree relatives. At present there is limited research linking these neuropsychological traits with genetic and neuroanatomical measures. In addition to improving the taxonomy of eating disorders, neuropsychological traits may be of value in producing targeted treatments.

MicroRNA-132 may play a role in coexistence of depression and cardiovascular disease: a hypothesis

Different individuals have different degrees of neuroplasticity due to their different experiences. Neuroplasticity may play a role in individual differences among neuropsychiatric disease treatment efficacy. Since the nervous system monitors and coordinates internal organ function, neuroplasticity may be associated with other diseases. Cardiovascular disease (CVD) is associated with depression, which is a disorder of disrupted neuroplasticity. MicroRNA-132 (miR-132) has a roles in neuroplasticity and cardiovascular function. Thus, we hypothesize that miR-132 may play a role in coexistence of depression and CVD.

Does risk for bipolar disorder heighten the disconnect between objective and subjective appraisals of cognition?

BACKGROUND

Deficits in cognitive functioning have been associated with bipolar disorder during episodes of depression and mania, as well as during periods of symptomatic remission. Separate evidence suggests that patients may lack awareness of these deficits and may even be overly confident with self-appraisals. The extent to which these separately or together represent prodromes of the disorder versus a consequence of the disorder remains unclear. The present study sought to test whether risk for bipolar disorder in a younger, college-aged cohort of individuals would be associated with lower performance in cognitive ability yet higher self-appraisal of cognitive functioning.

METHOD

Participants (N=128) completed an objective measure of working memory, a self-report measure of everyday cognitive deficits, and a measure associated with risk for bipolar disorder.

RESULTS

Contrary to expectation, risk for bipolar disorder did not significantly predict poorer working memory. However, a person's risk for bipolar disorder was associated with higher self-appraisal of cognitive functioning relative to those with lower risk despite there being no indication of a difference in ability on the working memory task.

LIMITATIONS

Participant recruitment relied on an analog sample; moreover, assessment of cognitive functioning was limited to working memory.

CONCLUSIONS

Results add to a growing body of evidence indicating that overconfidence may be part of the cognitive profile of individuals at risk for bipolar disorder.

Genetic and neurocognitive foundations of emotion abnormalities in bipolar disorder

INTRODUCTION

Bipolar Disorder (BD) is a serious mood disorder, the aetiology of which is still unclear. The disorder is characterised by extreme mood variability in which patients fluctuate between markedly euphoric, irritable, and elevated states to periods of severe depression. The current research literature shows that BD patients demonstrate compromised neurocognitive ability in addition to these mood symptoms. Viable candidate genes implicated in neurocognitive and socioemotional processes may explain the development of these core emotion abnormalities. Additionally, links between faulty neurocognition and impaired socioemotional ability complement genetic explanations of BD pathogenesis. This review examines associations between cognition indexing prefrontal neural regions and socioemotional impairments including emotion processing and regulation. A review of the effect of COMT and TPH2 on these functions is also explored.

METHODS

Major computer databases including PsycINFO, Google Scholar, and Medline were consulted in order to conduct a comprehensive review of the genetic and cognitive literature in BD.

RESULTS

This review determines that COMT and TPH2 genetic variants contribute susceptibility to abnormal prefrontal neurocognitive function which oversees the processing and regulation of emotion. This provides for greater understanding of some of the emotional and cognitive symptoms in BD.

CONCLUSIONS

Current findings in this direction show promise, although the literature is still in its infancy and further empirical research is required to investigate these links explicitly.

Increased neuroplasticity may protect against cardiovascular disease

Neuroplasticity refers to the capacity of the nervous system to modify its organization such that the brain can be shaped by environmental input. Individuals exhibit different degrees of neuroplasticity because of their different courses of growth. Neuroplasticity may thus play a role in individual differences in the treatment of neuropsychiatric diseases. The nervous system monitors and coordinates internal organ function. Thus neuroplasticity may also be associated with the pathogenesis and the treatment of some other diseases besides neuropsychiatric diseases. The cardiovascular system is controlled by the nervous system, mainly by the autonomic nervous system. Stress may lead to depression and cardiovascular disease (CVD). CVD is associated with depression, which is a disorder of decreased neuroplasticity. And the mechanisms of depression and CVD are related. So we conclude that decreased neuroplasticity causes the coexistence of depression with CVD, and increased neuroplasticity may be beneficial against the development of CVD. This theory provides another angle that can explain some of the reported phenomena related to CVD and neuropsychiatry and provide a potential treatment to protect against CVD.

[Schizophrenia and/or bipolar disorder: the neurocognitive endophenotypes]

Although Kraepelinian dichotomous conceptualization of psychosis was historically beneficial, modern studies do not support the existence of a sub-typing of psychotic illnesses into schizophrenic and affective psychoses. Years of intensive investigation on the genetic bases of schizophrenia and bipolar disorder suggest that these disorders, rather than being wholly distinct disorders, share common genetic risks. However, one of the most serious difficulties for genetic research in these illnesses is their enormous phenotypic heterogeneity. A response to this problem is the use of neurocognitive functions as endophenotypes or intermediate phenotypes. A review of the literature suggests that in both schizophrenia and bipolar disorder, neurocognitive functions are influenced by genetic factors and that there exists neuropsychological deficits in the nonaffected relatives of probands. However, it is unclear whether or not patterns of performance on neurocognitive tasks across probands as well as unaffected family members offer potential for identifying shared and illness-specific neurocognitive phenotypes for schizophrenia and bipolar disorder. Overlapping and unique neurocognitive endophenotypic signatures of the two psychoses are comprehensively described.

Assessing the potential to use neurocognition to predict who is at risk for developing bipolar disorder: a review of the literature

INTRODUCTION

The importance of early intervention strategies has recently been recognised in the field of psychiatry. Although early intervention strategies in schizophrenia have been extensively studied, recent efforts to identify individuals who are at increased risk for other disorders, such as bipolar disorder, have gained significant interest. There is some available data to suggest that cognitive deficits may precede the onset of mania; therefore, it would be beneficial to identify cognitive predictors of bipolar disorder in an effort to facilitate early intervention.

METHODS

We conducted a literature review of conscript, cohort, high-risk, family-based and first-episode mania studies that assessed neurocognition in order to ascertain potential cognitive predictors of bipolar disorder.

RESULTS

There is little evidence that individuals at risk for bipolar disorder exhibit deficits in global measures of neurocognition, such as IQ. However, deficits in specific neurocognitive domains, including verbal memory and executive function, appear to represent potential predictors of bipolar disorder.

CONCLUSIONS

These conclusions are preliminary; however, they provide a starting point for future work. Additional efforts towards understanding both the clinical and cognitive prodrome will be important in elucidating the pathophysiology of bipolar disorder.

Mood-stabilizing drugs: mechanisms of action

Mood-stabilizing drugs are the most widely prescribed pharmacological treatments for bipolar disorder, a disease characterized by recurrent episodes of mania and depression. Despite extensive clinical utilization, significant questions concerning their mechanisms of action remain. In recent years, a diverse set of molecular and cellular targets of these drugs has been identified. Based on these findings, downstream effects on neural and synaptic plasticity within key circuits have been proposed. Here, we discuss recent data, identify current challenges impeding progress and define areas for future investigation. Further understanding of the primary targets and downstream levels of convergence of mood-stabilizing drugs will guide development of novel therapeutic strategies and help translate discoveries into more effective treatments with less burdensome adverse-effect profiles.

Structure-function associations in hippocampus in bipolar disorder

Hippocampus volume decreases and verbal memory deficits have been reported in bipolar disorder (BD) as independent observations. We investigated potential associations between these deficits in subjects with BD. Hippocampus volumes were measured on magnetic resonance images of 31 subjects with BD and 32 healthy comparison (HC) subjects. The California Verbal Learning Test-Second Edition (CVLT) assessed verbal memory function in these subjects. Compared to the HC group, the BD group showed both significantly smaller hippocampus volumes and impaired performance on CVLT tests of immediate, short delay and long delay cued and free recall. Further, smaller hippocampus volume correlated with impaired performance in BD. Post hoc analyses revealed a trend towards improved memory in BD subjects taking antidepressant medications. These results support associations between morphological changes in hippocampus structure in BD and verbal memory impairment. They provide preliminary evidence pharmacotherapy may reverse hippocampus-related memory deficits.

Cognitive endophenotypes of psychosis within dimension and diagnosis

This study sought to characterize the psychosis phenotype, contrasting cognitive features within traditional diagnosis and psychosis dimension in a family sample containing both schizophrenia and psychotic bipolar I disorder. Seventy-six probands with psychosis [44 probands with schizophrenia, 32 probands with psychotic bipolar I disorder] and 55 first-degree relatives [30 relatives of schizophrenia probands, 25 relatives of bipolar probands] were recruited. Standardized clinical and neuropsychological measures were administered. No differences in cognitive performance emerged between probands with schizophrenia and probands with psychotic bipolar disorder, or between relatives of probands with schizophrenia and relatives of probands with bipolar disorder in the domains of working and declarative memory, executive function and attention. Relatives overall showed higher cognitive performance compared to probands, as expected. However, when we segmented the probands and relatives along a psychosis dimension, independent of diagnostic groups, results revealed lower cognitive performance in probands compared to relatives without psychosis spectrum disorders, whereas relatives with psychosis spectrum disorders showed an intermediate level of performance across all cognitive domains. In this study, cognitive performance did not distinguish either probands or their first-degree relatives within traditional diagnostic groups (schizophrenia and psychotic bipolar disorder), but distinguished probands and relatives with and without lifetime psychosis manifestations independent of diagnostic categories. These data support the notion that schizophrenia and psychotic bipolar disorder present a clinical continuum with overlapping cognitive features defining the psychosis phenotype.

Emotional bias in unaffected siblings of patients with bipolar I disorder

BACKGROUND

Bipolar disorder (BPD) research has identified a number of neurocognitive deficits as potential vulnerability markers; however, very few studies have focused on patterns of performance on affective processing tasks (e.g. affective Go/No-Go tasks) which may be more closely tied to the pathophysiology of the illness. We previously reported that stable BPD patients demonstrate a response bias toward negative affective stimuli as compared with healthy controls and schizophrenia patients. The goal of the current study was to expand upon these prior findings to investigate these patterns in the unaffected siblings of BPD patients.

METHODS

An affective Go/No-Go test was used to evaluate inhibitory response to negatively-valenced, positively-valenced, and neutral stimuli in 20 unaffected siblings of bipolar I patients versus 20 healthy controls. Accuracy (d') and response bias (beta) served as dependent variables in a series of repeated measures ANCOVAs.

RESULTS

We found a non-significant main effect for group when comparing accuracy performance (d') on the affective Go/No-Go of unaffected siblings versus healthy controls. However, very similar to the pattern that we previously reported in stable BPD patients, unaffected siblings showed a response bias (beta) toward negatively-valenced stimuli versus healthy controls [F=3.81; p=0.03].

LIMITATIONS

Small sample size.

CONCLUSIONS

The current results extend our recent work which suggested that stable bipolar patients attend more readily to negative target stimuli than do schizophrenic or healthy subjects. These data, indicating that unaffected siblings also demonstrate an affective processing bias, implicate this task as a potential endophenotype in BPD.

Brain functional domains inform therapeutic interventions in attention-deficit/hyperactivity disorder and pediatric bipolar disorder

A deeper understanding of how the relationships between impulsivity, reward systems and executive function deficits may be similar or different in attention-deficit/hyperactivity disorder (ADHD) and pediatric bipolar disorder (PBD) is fundamental for better defining phenotypy in these two developmental illnesses, and moving towards improved treatment and intervention. We focus our article on recent neurocognitive and neuroimaging data examining the behavioral and neural aspects of poor behavior regulation, response inhibition and reward systems in ADHD and PBD. In light of recent research evidence, we propose that the common behavioral manifestations of impulsivity in ADHD and PBD may indeed originate from different neural mechanisms mediated by altered reward systems. In order to define and differentiate these mechanisms, unlike previous approaches, our theoretical model examines the interface of the dorsal frontostriatal circuit, involved in behavior regulation, and the ventral frontostriatal circuit, which is involved in reward-related and affect processes. Preliminary evidence suggests that the neural systems involved in impulsivity, reward systems and executive function engage differently in the two illnesses. In PBD, 'emotional impulsivity' is predominantly 'bottom-up' and emotionally/motivationally driven, and stems from ventral frontostriatal circuitry dysfunction. By contrast, in ADHD 'cognitive impulsivity' is predominantly 'top-down' and more 'cognitively driven', and stems from dorsal frontostriatal dysfunction. We discuss this evidence in view of clinically relevant questions and implications for illness-based intervention. We conclude that the reward-related mechanisms underlying the interactions between executive function, behavior regulation and impulsivity in PBD and ADHD may be differentially compromised, and in accordance differently shape the clinical symptoms of impulsivity and goal-directed behavior.

Cognitive functions among euthymic bipolar I patients after a single manic episode versus recurrent episodes

BACKGROUND

There is a growing consensus that persistent cognitive deficits are common in patients with bipolar disorders even when they are euthymic.

AIM

The aim was to assess objectively the presence of cognitive deficits in bipolar patients in remission, and to correlate these deficits with the recurrence of the disease.

METHODS

Cognitive functions (executive function, memory, intelligence, attention and concentration) of a group of euthymic bipolar patients after a single manic episode were compared to cognitive functions of patients who experienced recurrent episodes, both groups were assessed during remission. The results were compared with a control group, using SPSS.

RESULTS

Euthymic bipolar patients assessed after a single manic episode showed impairment in attention, executive functions and total memory score in comparison to healthy control subjects. While they performed better than Euthymic bipolar patients assessed after recurrent bipolar episodes as regards attention and executive function.

CONCLUSION

Bipolar disorder is associated with attention, memory and executive dysfunction. Attention and executive dysfunction is deteriorated by the recurrence of bipolar episodes.

Genetic variation in cholinergic muscarinic-2 receptor gene modulates M2 receptor binding in vivo and accounts for reduced binding in bipolar disorder

Genetic variation in the cholinergic muscarinic-2 (M(2)) receptor gene (CHRM2) has been associated with the risk for developing depression. We previously reported that M(2)-receptor distribution volume (V(T)) was reduced in depressed subjects with bipolar disorder (BD) relative to depressed subjects with major depressive disorder (MDD) and healthy controls (HCs). In this study, we investigated the effects of six single-nucleotide polymorphisms (SNPs) for CHRM2 on M(2)-receptor binding to test the hypotheses that genetic variation in CHRM2 influences M(2)-receptor binding and that a CHRM2 polymorphism underlies the deficits in M(2)-receptor V(T) observed in BD. The M(2)-receptor V(T) was measured using positron emission tomography and [(18)F]FP-TZTP in unmedicated, depressed subjects with BD (n=16) or MDD (n=24) and HCs (n=25), and the effect of genotype on V(T) was assessed. In the controls, one SNP (with identifier rs324650, in which the ancestral allele adenine (A) is replaced with one or two copies of thymine (T), showed a significant allelic effect on V(T) in the pregenual and subgenual anterior cingulate cortices in the direction AA<AT<TT. In contrast, in BD subjects with the TT genotype, V(T) was significantly lower than in BD subjects with the AT genotype in these regions. The BD subjects homozygous for the T -allele also showed markedly lower V(T) (by 27 to 37% across regions) than HCs of the same genotype. Post hoc analyses suggested that T homozygosity was associated with a more severe illness course, as manifested by lower socioeconomic function, poorer spatial recognition memory and a greater likelihood of having attempted suicide. These data represent novel preliminary evidence that reduced M(2)-receptor V(T) in BD is associated with genetic variation within CHRM2. The differential impact of the M(2)-receptor polymorphism at rs324650 in the BD and HC samples suggests interactive effects with an unidentified vulnerability factor for BD.

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.

Hippocampal morphology in lithium and non-lithium-treated bipolar I disorder patients, non-bipolar co-twins, and control twins

BACKGROUND

Bipolar I disorder is a highly heritable psychiatric illness with undetermined predisposing genetic and environmental risk factors. We examined familial contributions to hippocampal morphology in bipolar disorder, using a population-based twin cohort design.

METHODS

We acquired high-resolution brain MRI scans from 18 adult patients with bipolar I disorder [BPI; mean age 45.6 ± 8.69 (SD); 10 lithium-treated], 14 non-bipolar co-twins, and 32 demographically matched healthy comparison twins. We used three-dimensional radial distance mapping techniques to visualize hippocampal shape differences between groups.

RESULTS

Lithium-treated BPI patients had significantly larger global hippocampal volume compared to both healthy controls (9%) and non-bipolar co-twins (12%), and trend-level larger volumes relative to non-lithium-treated BPI patients (8%). In contrast, hippocampal volumes in non-lithium-treated BPI patients did not differ from those of non-bipolar co-twins and control twins. 3D surface maps revealed thicker hippocampi in lithium-treated BPI probands compared with control twins across the entire anterior-to-posterior extent of the cornu ammonis (CA1 and 2) regions, and the anterior part of the subiculum. Unexpectedly, co-twins also showed significantly thicker hippocampi compared with control twins in regions that partially overlapped those showing effects in the lithium treated BPI probands.

CONCLUSIONS

These findings suggest that regionally thickened hippocampi in bipolar I disorder may be partly due to familial factors and partly due to lithium-induced neurotrophy, neurogenesis, or neuroprotection. Unlike schizophrenia, hippocampal alterations in co-twins of bipolar I disorder probands are likely to manifest as subtle volume excess rather than deficit, perhaps indicating protective rather than risk effects.

Deficits in visual sustained attention differentiate genetic liability and disease expression for schizophrenia from Bipolar Disorder

BACKGROUND

There is mounting evidence for shared genetic liability to psychoses, particularly with respect to Schizophrenia (SZ) and Bipolar Disorder (BD), which may also involve aspects of cognitive dysfunction. Impaired sustained attention is considered a cardinal feature of psychoses but its association with genetic liability and disease expression in BD remains to be clarified.

METHODS

Visual sustained attention was assessed using the Degraded Symbol Continuous Performance Test (DS-CPT) in a sample of 397 individuals consisting of 50 remitted SZ patients, 119 of their first degree relatives, 47 euthymic BD patients, 88 of their first degree relatives and 93 healthy controls. Relatives with a personal history of schizophrenia or bipolar spectrum disorders were excluded. Performance on the DS-CPT was evaluated based on the response criterion (the amount of perceptual evidence required to designate a stimulus as a target) and sensitivity (a signal-detection theory measure of signal/noise discrimination).

RESULTS

We found no effect of genetic risk or diagnosis for either disorder on response criterion. In contrast, impaired sensitivity was seen in SZ patients and to a lesser degree in their relatives but not in BD patients and their relatives. These findings were not attributable to IQ, medication, age of onset or duration of illness.

CONCLUSIONS

Our results argue for the specificity of visual sustained attention impairment in differentiating SZ from BD. They also suggest that compromised visual information processing is a significant contributor to these deficits in SZ.

Sustained attention as a potential endophenotype for bipolar disorder

OBJECTIVE

Nowadays, it is accepted that to identify the biological basis of psychiatric illnesses it would be useful to deconstruct them into the most basic manifestations, such as cognitive deficits. The aim of this study was to set attention deficit as a stable vulnerability marker of bipolar disorder.

METHOD

Sustained attention was evaluated by the Continuous Performance Test (DS-CPT) in 143 euthymic bipolar patients and 105 controls. To estimate the influence of clinical profile in attention, patients completed a semi-structured interview.

RESULTS

Bipolar patients showed a deficit in attention during euthymic periods. This disturbance correlated with years of evolution, age of onset and age of first hospitalisation; and was not influenced by other clinical data.

CONCLUSION

Sustained attention may be considered as an endophenotype of the illness.

Impairment of verbal learning and memory and executive function in unaffected siblings of probands with bipolar disorder

OBJECTIVES

Impairments in executive function and memory have been reported in relatives of patients with bipolar disorder, suggesting that they could be potential endophenotypes for genetic studies, but the findings are inconsistent. In this study, neuropsychological performance in unaffected siblings of probands with family loading for bipolar disorder is compared to that of individually matched healthy controls. We hypothesized that performance on tests of executive functions and memory would be impaired in unaffected siblings of probands with bipolar disorder compared to matched healthy controls.

METHODS

We evaluated 30 unaffected siblings of probands with bipolar I disorder and 30 individually matched healthy controls using tests of attention, executive function, and memory. Unaffected siblings and healthy control subjects did not differ with respect to gender, age, and years of education.

RESULTS

Unaffected siblings performed poorly on the Tower of London test (TOL), the Rey's auditory verbal learning test (RAVLT), and the Rey's complex figure test. In the multivariate analysis, significance was noted for the TOL, total number of moves (p = 0.007) and the RAVLT total learning score (p = 0.001).

CONCLUSIONS

Our study suggests that the deficits in verbal learning and memory and executive functions (planning) could be potential endophenotypes in bipolar disorder. These deficits are consistent with the proposed neurobiological model of bipolar disorder involving the frontotemporal and subcortical circuits. Future studies could couple cognitive and imaging strategies and genomics to identify neurocognitive endophenotypes in bipolar disorder.

Phospholipid profile in the postmortem hippocampus of patients with schizophrenia and bipolar disorder: no changes in docosahexaenoic acid species

Previous studies with postmortem brain tissues showed abnormalities not only in n-3 long-chain polyunsaturated fatty acids (PUFA) but also in phospholipid metabolism in the cortex of individuals with schizophrenia and mood disorder. In this study we investigated whether there is similar abnormality in n-3 long-chain PUFAs and/or in phospholipid profile in the hippocampus of schizophrenia and bipolar disorder patients compared to unaffected controls. Using high-performance liquid chromatography/electrospray ionization-mass spectrometry (LC/MS), the phospholipid contents in the postmortem hippocampus from 35 individuals with schizophrenia, 34 individuals with bipolar disorder and 35 controls were evaluated. Unlike the previous findings form orbitofrontal cortex, we found no significant differences in either n-3 long-chain PUFA or total phosphatidylserine (PS), phosphatidylethanolamine (PE) and phosphatidylcholine (PC). However, docosapentaenoic acid (n-6, 22:5n-6)-PS and 22:5n-6-PC were significantly lower in individuals with schizophrenia or bipolar disorder than the controls. When fatty acid contents were estimated from PS, PE and PC, 22:5n-6 was significantly lower in both patient groups compared to the controls. From these results we concluded that DHA loss associated with these psychiatric disorders may be specific to certain regions of the brain. The selective decrease in 22:5n-6 without affecting DHA contents suggests altered lipid metabolism, particularly n-6 PUFA rather than n-3 PUFA, in the hippocampus of individuals with schizophrenia or bipolar disorder.

Genetics and intermediate phenotypes of the schizophrenia--bipolar disorder boundary

Categorization of psychotic illnesses into schizophrenic and affective psychoses remains an ongoing controversy. Although Kraepelinian subtyping of psychosis was historically beneficial, modern genetic and neurophysiological studies do not support dichotomous conceptualization of psychosis. Evidence suggests that schizophrenia and bipolar disorder rather present a clinical continuum with partially overlapping symptom dimensions, neurophysiology, genetics and treatment responses. Recent large scale genetic studies have produced inconsistent findings and exposed an urgent need for re-thinking phenomenology-based approach in psychiatric research. Epidemiological, linkage and molecular genetic studies, as well as studies in intermediate phenotypes (neurocognitive, neurophysiological and anatomical imaging) in schizophrenia and bipolar disorders are reviewed in order to support a dimensional conceptualization of psychosis. Overlapping and unique genetic and intermediate phenotypic signatures of the two psychoses are comprehensively recapitulated. Alternative strategies which may be implicated into genetic research are discussed.