Meta-analysis of longitudinal studies of cognition in bipolar disorder: comparison with healthy controls and schizophrenia

Neurocognitive heterogeneity in young offspring of patients with bipolar disorder: The effect of putative clinical stages

BACKGROUND

Bipolar disorder (BD) is associated with significant cognitive heterogeneity. In recent years, a number of studies have investigated cognitive subgroups in BD using data-driven methods and found that BD includes several subgroups including a severely impaired and a neurocognitively intact cluster. Studies in offspring of BD (BDoff) are particularly important to establish the timing of emergence of cognitive subgroups but studies investigating cognitive heterogeneity in BDoff are lacking. Our aim was to investigate cognitive heterogeneity in BDoff and the relationship between cognitive heterogeneity and putative clinical stages of BD.

METHODS

Seventy-one euthymic BDoff and 50 healthy controls were assessed using clinical measures and a battery of neuropsychological tests. Neurocognitive subgroups were investigated using latent class analysis.

RESULTS

Three neurocognitive subgroups, including a severe impairment group, a good performance cluster, and a subgroup characterized by intermediate/selective impairment was found. Both severe and intermediate level impairment subgroups underperformed healthy controls in processing speed, verbal fluency, visual memory and working memory. Deficits in verbal memory and executive functions were only evident in severe impairment subgroup. The putative stage of the illness had no significant effect on cognitive clustering of BDoff. Trait impulsivity scores were significantly increased in severe and intermediate impairment clusters but not in the cognitively good functioning subgroup of BDoff.

LIMITATIONS

The cross-sectional nature of the study was the main consideration.

CONCLUSION

These results suggest that cognitive heterogeneity is premorbid characteristic of BD and cognitive subgroups of BDoff emerge prior to the onset of illness and prodromal symptoms.

Abnormalities of Alpha Activity in Frontocentral Region of the Brain as a Biomarker to Diagnose Adolescents With Bipolar Disorder

Objectives. To investigate brain abnormalities in adolescents with new-onset bipolar disorder (BD) during acute hypomanic and depressive episodes using electroencephalogram (EEG) analysis and to derive a computer-based method for diagnosis of the disorder. Methods. EEG spectral power and entropy of 21 adolescents with BD (included 11 patients in the hypomanic episode and 10 patients in the depressive episode) and 18 healthy adolescents were compared. Moreover, using significant differences and K-nearest-neighbors (KNN) classifier, it was attempted to distinguish the BD adolescents from normal ones. Results. The BD adolescents had higher values of spectral power in all frequency bands, particularly in the frontocentral, mid-temporal, and right parietal regions. Also, spectral entropy had significantly increased in delta, alpha, and gamma frequency bands for BD. A high accuracy of 95.8% was achieved by all significant differences in the alpha band in discriminating adolescents with BD. The depressive state showed higher values of spectral power and entropy in low-frequency bands (delta and theta) compared to the hypomanic state. Conclusion. Based on BD symptoms, especially inattention, increased alpha power is a rational finding which is associated with thalamus dysfunction. Thus, it seems that EEG alpha oscillation is the main source of abnormality in BD. Furthermore, EEG slowing in the depressive episode is related to inhibition of electrical activity and reduced cognitive functions.

A symptom-based continuum of psychosis explains cognitive and real-world functional deficits better than traditional diagnoses

BACKGROUND

Patients with psychotic spectrum disorders share overlapping clinical/biological features, making it often difficult to separate them into a discrete nosology (i.e., Diagnostic and Statistical Manual of Mental Disorders [DSM]).

METHODS

The current study investigated whether a continuum classification scheme based on symptom burden would improve conceptualizations for cognitive and real-world dysfunction relative to traditional DSM nosology. Two independent samples (New Mexico [NM] and Bipolar and Schizophrenia Network on Intermediate Phenotypes [B-SNIP]) of patients with schizophrenia (NM: N = 93; B-SNIP: N = 236), bipolar disorder Type I (NM: N = 42; B-SNIP: N = 195) or schizoaffective disorder (NM: N = 15; B-SNIP: N = 148) and matched healthy controls (NM: N = 64; B-SNIP: N = 717) were examined. Linear regressions examined how variance differed as a function of classification scheme (DSM diagnosis, negative and positive symptom burden, or a three-cluster solution based on symptom burden).

RESULTS

Symptom-based classification schemes (continuous and clustered) accounted for a significantly larger portion of captured variance of real-world functioning relative to DSM diagnoses across both samples. The symptom-based classification schemes accounted for large percentages of variance for general cognitive ability and cognitive domains in the NM sample. However, in the B-SNIP sample, symptom-based classification schemes accounted for roughly equivalent variance as DSM diagnoses. A potential mediating variable across samples was the strength of the relationship between negative symptoms and impaired cognition.

CONCLUSIONS

Current results support suggestions that a continuum perspective of psychopathology may be more powerful for explaining real-world functioning than the DSM diagnostic nosology, whereas results for cognitive dysfunction were sample dependent.

Impact of number of episodes on neurocognitive trajectory in bipolar disorder patients: a 5-year follow-up study

BACKGROUND

The neurocognitive trajectory in bipolar disorder (BD) is variable, with controversial findings, and most evidence come from cross-sectional studies. We aimed to examine the course of neurocognitive functioning in a sample of euthymic BD patients in comparison with a control group during a 5-year follow-up.

METHODS

Ninety-nine euthymic bipolar patients and 40 healthy controls were assessed using a comprehensive neurocognitive battery (six neurocognitive domains) at baseline (T1) and then at 5-year follow-up (T2) in a longitudinal study.

RESULTS

No evidence of a progression in neurocognitive dysfunction was found either in cognitive composite index or in any of the neurocognitive domains for the whole cohort. However, there was a negative correlation between number of manic episodes and hospitalisations due to manic episodes and change in neurocognitive composite index (NCI) during the follow-up. Moreover, patients with higher number of manic and hypomanic episodes have a greater decrease in NCI, working memory and visual memory. History of psychotic symptoms was not related to the trajectory of neurocognitive impairment.

CONCLUSIONS

Our results suggest that, although the progression of cognitive decline is not a general rule in BD, BD patients who have a greater number of manic or hypomanic episodes may constitute a subgroup characterised by the progression of neurocognitive impairment. Prevention of manic and hypomanic episodes could have a positive impact on the trajectory of cognitive function.

The Role of Docosahexaenoic Acid (DHA) on Cognitive Functions in Psychiatric Disorders

Cognitive impairment is strongly associated with functional outcomes in psychiatric patients. Involvement of n-3 long chain polyunsaturated fatty acid (n-3 LC-PUFA), in particular docosahexaenoic acid (DHA), in brain functions is largely documented. DHA is incorporated into membrane phospholipids as structural component, especially in the central nervous system where it also has important functional effects. The aim of this review is to investigate the relationship between DHA and cognitive function in relation to mental disorders. Results from few randomized controlled trials (RCTs) on the effects of DHA (alone or in combination) in psychotic, mood and neurodevelopmental disorders, respectively, suggest that no conclusive remarks can be drawn.

Neurococognitive and neuroimaging correlates of obesity and components of metabolic syndrome in bipolar disorder: a systematic review

BACKGROUND

Individuals with bipolar disorder (BD) have a higher prevalence of obesity and metabolic syndrome (MetS) compared with the general population. Obesity and MetS are associated with cognitive deficits and brain imaging abnormalities in the general population. Obesity and components of MetS might potentially associate with neuroimaging and neurocognitive findings in BD.

METHODS

A literature search of studies investigating the association between obesity (and other components of MetS) and neurocognitive and neuroimaging findings in BD was conducted. In addition to a systematic review, a random-effects meta-analysis was conducted when sufficient data were available.

RESULTS

Twenty-three studies were included in the current systematic review. Overweight/obese patients were significantly associated with impaired neurocognition compared normal weight individuals with BD (d = 0.37). The most robust association between obesity and cognitive deficits in BD was observed in the cognitive subdomain of executive functions (d = 0.61). There was also evidence for a significant relationship between cognitive impairment in BD and other components of MetS including hypertension, dyslipidemia, and diabetes. Overweight/obese individuals with BD had more pronounced brain imaging abnormalities than normal weight individuals with BD.

CONCLUSIONS

Obesity and related cardiovascular risk factors significantly are associated with more severe cognitive and brain imaging abnormalities in BD. Medical co-morbidities can potentially contribute to functional decline observed in some patients throughout the course of BD.

Cognitive Deficits in Euthymic Patients With Bipolar Disorder: State or Trait Marker?

Cognitive deficits have been demonstrated in people in the euthymic phase of bipolar disorder. This cross-sectional study compared euthymic bipolar disorder patients (n = 30) with never psychiatrically ill controls (n = 30) on a neuropsychological test battery containing tasks of executive function, the Wisconsin Card Sorting Test (WCST), attention and working memory, digits forward and backward, and speed of information processing digit symbol. Scores on the Mini-Mental State Examination (MMSE) and vocabulary test did not differ between the groups. The bipolar group was significantly impaired compared with controls on various indices of executive function on the WCST and on the digit tests. The impaired performance on the digit tests, but not the WCST, was significantly associated with medication status, notably prescribed benzodiazepines. There was no significant effect of severity or course of illness on performance. The findings support the hypothesis that impairments in executive function are present between illness episodes in bipolar disorder, and so they are not simply state markers.

Neurocognition and functional outcome in patients with psychotic, non-psychotic bipolar I disorder, and schizophrenia. A five-year follow-up

Background:

Bipolar disorder (BD) and schizophrenia (SZ) are characterized by neurocognitive and functional deficits with marked heterogeneity. It has been suggested that BD with a history of psychotic symptoms (BD-P) could constitute a phenotypically homogeneous subtype characterized by greater neurocognitive and functional impairments, or by a distinct trajectory of such deficits. The aim of this study was to compare the neurocognitive and functional course of euthymic BD-P, euthymic BD patients without a history of psychosis (BD-NP), stabilized patients with schizophrenia and healthy subjects, during a five-year follow-up.

Methods:

Neurocognitive and psychosocial function was examined in 100 euthymic patients with BD (50 BD-P, 50 BD-NP), 50 stabilized patients with schizophrenia (SZ), and 51 healthy controls (HC) at baseline (T1), and after a 5-year follow-up (T2).

Results:

The course of both neurocognitive performance and functional outcome of patients with SZ and BD (BD-P and BD-NP) is stable. The profile of neurocognitive impairment of patients with SZ or BD (BD-P and BD-NP), is similar, with only quantitative differences circumscribed to certain domains, such as working memory. The subgroup of patients with BD-NP does not show functional deterioration.

Conclusions:

We have not found evidence of progression in the neurocognitive or psychosocial impairment in any of the three groups of patients, although it cannot be dismissed the possibility of a subset of patients with a progressive course. Other longitudinal studies with larger samples and longer duration are necessary to confirm these findings.

Predictors of cognitive performance in bipolar disorder: The role of educational degree and inflammatory markers

BACKGROUND

The aim of this article was to evaluate the cognitive status of remitted patients with bipolar disorder (BD) using Mini-Mental State Examination (MMSE), Frontal Assessment Battery, and Brief Assessment of Cognition in Affective Disorders (BAC-A). The BAC-A is a comprehensive test battery addressing the cognitive domains compromised in BD. We also aimed to analyze potential clinical and immune predictors of cognitive performance in BD.

METHODS

Remitted patients with BD (M ± S.E: 43.80 ± 10.87 years) and age-matched controls (M ± S.E: 43.52 ± 11.72) were administered clinical questionnaires and cognitive tests. Inflammatory plasma levels (IL-2, IL-4, IL-6, IL-10, IFN-γ, TNFα, IL-17A, sTNFR1, and sTNFR2) were measured using an enzyme-linked immunosorbent assay. We generated a global cognitive performance index based on BAC-A scores. Multivariate analyses compared cognitive and immune measures across groups. A regression analysis was performed to examine the relationship between global cognitive performance, clinical and immune parameters in BD.

RESULTS

Remitted patients with BD performed poorly on tasks of affective processing, verbal memory, working verbal memory, and executive functioning. Patients with BD presented higher plasma levels sTNFR1, TNFα, IFN, IL2, IL4, IL6, IL10, and IL17compared with controls. Education and MMSE were found to be positively correlated with global cognitive performance. IL6 plasma levels were negatively correlated with global cognitive performance.

CONCLUSION

The major determinants of poor cognitive performance in BD were education and IL6 plasma levels.

Cognitive Deficits in Psychotic Disorders: A Lifespan Perspective

Individuals with disorders that include psychotic symptoms (i.e. psychotic disorders) experience broad cognitive impairments in the chronic state, indicating a dimension of abnormality associated with the experience of psychosis. These impairments negatively impact functional outcome, contributing to the disabling nature of schizophrenia, bipolar disorder, and psychotic depression. The robust and reliable nature of cognitive deficits has led researchers to explore the timing and profile of impairments, as this may elucidate different neurodevelopmental patterns in individuals who experience psychosis. Here, we review the literature on cognitive deficits across the life span of individuals with psychotic disorder and psychotic-like experiences, highlighting the dimensional nature of both psychosis and cognitive ability. We identify premorbid generalized cognitive impairment in schizophrenia that worsens throughout development, and stabilizes by the first-episode of psychosis, suggesting a neurodevelopmental course. Research in affective psychosis is less clear, with mixed evidence regarding premorbid deficits, but a fairly reliable generalized deficit at first-episode, which appears to worsen into the chronic state. In general, cognitive impairments are most severe in schizophrenia, intermediate in bipolar disorder, and the least severe in psychotic depression. In all groups, cognitive deficits are associated with poorer functional outcome. Finally, while the generalized deficit is the clearest and most reliable signal, data suggests specific deficits in verbal memory across all groups, specific processing speed impairments in schizophrenia and executive functioning impairments in bipolar disorder. Cognitive deficits are a core feature of psychotic disorders that provide a window into understanding developmental course and risk for psychosis.

Longitudinal stability of cognitive control in early psychosis: Nondegenerative deficits across diagnoses

Cognitive impairment, particularly in the domain of cognitive control, is characteristic of schizophrenia (SZ) spectrum and bipolar disorders (BDs). The longitudinal trajectory of these impairments, however, remains unclear. Indeed, some studies have observed degeneration and others stability or even improvement over time in these illnesses. Here we examined the longitudinal stability of the AX-Continuous Performance Task (AX-CPT), a cognitive control task, in 52 patients with recent-onset SZ (<2 years from first study measurement), 20 patients with recent-onset BD Type I with psychotic features, and 70 healthy control subjects. Subjects performed the AX-CPT at 2 time points separated by an average of 365 days (range 270-620). Previously identified deficits in cognitive control were replicated in both patient groups. No effects of time or interactions between time and diagnosis were observed. Intraclass correlation coefficients also suggested AX-CPT performance was stable across time for all diagnostic groups. Although performance was stable on average, a positive association was noted between change in cognitive control and change in disorganization symptom severity across patient groups. In conclusion, the present findings suggest that deficits in cognitive control are present in both disorders and stable over the early course of psychotic illness. No evidence was observed for progression or deterioration of cognitive control or differential recovery in SZ compared to BD. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

Does Cognitive Dysfunction in Bipolar Disorder Qualify as a Diagnostic Intermediate Phenotype?-A Perspective Paper

The present perspective paper addresses and discusses whether cognitive dysfunction in bipolar disorder qualifies as a diagnostic intermediate phenotype using the Robin and Guze criteria of diagnostic validity. The paper reviews current data within (1) delineation of the clinical intermediate phenotype, (2) associations of the intermediate phenotype with para-clinical data such as brain imaging and blood-based data, (3) associations to family history / genetics, (4) characteristics during long-term follow-up, and (5) treatment effects on cognition. In this way, the paper identifies knowledge gaps and suggests recommendations for future research within each of the five areas. Based on the current state of knowledge, we conclude that cognitive dysfunction does not qualify as a diagnostic intermediate phenotype or endophenotype for bipolar disorder, although promising new evidence points to emotion and reward processing abnormalities as possible putative endophenotypes.

Neuron-glia Interaction as a Possible Pathophysiological Mechanism of Bipolar Disorder

Accumulating evidence has shown the importance of glial cells in the neurobiology of bipolar disorder. Activated microglia and inflammatory cytokines have been pointed out as potential biomarkers of bipolar disorder. Indeed, recent studies have shown that bipolar disorder involves microglial activation in the hippocampus and alterations in peripheral cytokines, suggesting a potential link between neuroinflammation and peripheral toxicity. These abnormalities may also be the biological underpinnings of outcomes related to neuroprogression, such as cognitive impairment and brain changes. Additionally, astrocytes may have a role in the progression of bipolar disorder, as these cells amplify inflammatory response and maintain glutamate homeostasis, preventing excitotoxicity. The present review aims to discuss neuron-glia interactions and their role in the pathophysiology and treatment of bipolar disorder.

Imaging Habenula Volume in Schizophrenia and Bipolar Disorder

The habenula (Hb), a bilateral nucleus located next to the dorsomedial thalamus, is of particular relevance to psychiatric disorders based on preclinical evidence linking the Hb to depressive and amotivational states. However, studies in clinical samples are scant because segmentation of the Hb in neuroimaging data is challenging due to its small size and low contrast from the surrounding tissues. Negative affective states dominate the clinical course of schizophrenia and bipolar disorder and represent a major cause of disability. Diagnosis-related alterations in the volume of Hb in these disorders have therefore been hypothesized but remain largely untested. To probe this question, we used a recently developed objective and reliable semi-automated Hb segmentation method based on myelin-sensitive magnetic resonance imaging (MRI) data. We ascertained case-control differences in Hb volume from high resolution structural MRI data obtained from patients with schizophrenia (n = 95), bipolar disorder (n = 44) and demographically matched healthy individuals (n = 52). Following strict quality control of the MRI data, the final sample comprised 68 patients with schizophrenia, 32 with bipolar disorder and 40 healthy individuals. Regardless of diagnosis, age, sex, and IQ were not correlated with Hb volume. This was also the case for age of illness onset and medication (i.e., antipsychotic dose and lithium-treatment status). Case-control differences in Hb volume did not reach statistical significance; their effect size (Cohen's d) was negligible on the left (schizophrenia: 0.14; bipolar disorder: -0.03) and small on the right (schizophrenia: 0.34; bipolar disorder: 0.26). Nevertheless, variability in the volume of the right Hb was associated with suicidality in the entire patient sample (ρ = 0.29, p = 0.004) as well as in each patient group (bipolar disorder: ρ = 0.34, p = 0.04; schizophrenia: ρ = 0.25, p = 0.04). These findings warrant replication in larger samples and longitudinal designs and encourage more comprehensive characterization of Hb connectivity and function in clinical populations.

Biological aspects and candidate biomarkers for rapid-cycling in bipolar disorder: A systematic review

Rapid-cycling bipolar disorder represents a frequent severe subtype of illness which has been associated with poor response to pharmacological treatment. Aim of the present article is to provide an updated review of biological markers associated with rapid-cycling bipolar disorder. A research in the main database sources has been conducted to identify relevant papers about the topic. Rapid-cycling bipolar disorder patients seem to have a more frequent family history for bipolar spectrum disorders (d range: 0.44-0.74) as well as an increased susceptibility to DNA damage or mRNA hypo-transcription (d range: 0.78-1.67) than non rapid-cycling ones. A susceptibility to hypothyroidism, which is exacerbated by treatment with lithium, is possible in rapid-cycling bipolar disorder, but further studies are needed to draw definitive conclusions. Rapid-cycling bipolar patients might have more insuline resistance as well as more severe brain changes in frontal areas (d range: 0.82-0.94) than non rapid-cycling ones. Many questions are still open about this topic. The first is whether the rapid-cycling is inheritable or is more generally the manifestation of a severe form of bipolar disorder. The second is whether some endocrine dysfunctions (diabetes and hypothyroidism) predispose to rapid-cycling or rapid-cycling is the consequence of drug treatment or medical comorbidities (e.g. obesity).