Cognitive endophenotypes in a family with bipolar disorder with a risk locus on chromosome 4

Verbal fluency in schizophrenia and bipolar disorder - A longitudinal, family study

Verbal fluency (VF) has been proposed as a putative neurocognitive endophenotype in schizophrenia (SZ) and bipolar disorder (BD). However, this hypothesis has not been examined using a longitudinal family approach. We conducted a five-group, comparative study. The sample comprised 323 adult participants, including 81 BD patients, 47 unaffected relatives of BD BD-Rel), 76 SZ patients, 40 unaffected relatives of SZ (SZ-Rel), and 79 genetically unrelated healthy controls (HC). All subjects were assessed twice with semantic VF (sem-VF) and phonological VF (ph-VF) tests over a 2-year follow-up period. ANCOVAs controlling for age and years of education were used to compare performance across groups. Patients with SZ and BD and their unaffected relatives showed sem-VF and ph-VF deficits at baseline, which persisted over time (all, p < 0.05). Moreover, BD-Rel showed an intermediate performance between SZ and HC. A repeated-measures ANOVA revealed no significant differences in the between-group trajectories comparison (p > 0.05). Our findings support that VF may represent a neurocognitive endophenotype for SZ and BD. Further longitudinal, family studies are warranted to confirm this preliminary evidence.

Endophenotypes of executive functions in obsessive compulsive disorder? A meta-analysis in unaffected relatives

Endophenotypes are mediator traits between genetic influences and clinical phenotypes. Meta-analyses have consistently shown modest impairments of executive functioning in obsessive compulsive disorder (OCD) patients compared to healthy controls. Similar deficits have also been reported in unaffected relatives of OCD patients, but have not been quantified. We conducted the first meta-analysis combining all studies investigating executive functioning in unaffected relatives of individuals with OCD to quantify any deficits. A search of Pubmed, Medline and PsychInfo databases identified 21 suitable papers comprising 707 unaffected relatives of OCD patients and 842 healthy controls. Effect sizes were calculated using random effects models. Unaffected relatives displayed a significant impairment in global executive functioning. Analyses of specific executive functioning subdomains revealed impairments in: planning, visuospatial working memory and verbal fluency. Deficits in executive functioning are promising endophenotypes for OCD. To identify further biomarkers of disease risk/resilience in OCD, we suggest examining specific executive functioning domains.

Visual memory dysfunction as a neurocognitive endophenotype in bipolar disorder patients and their unaffected relatives. Evidence from a 5-year follow-up Valencia study

BACKGROUND

Scarce research has focused on Visual Memory (VM) deficits as a possible neurocognitive endophenotype of bipolar disorder (BD). The main aim of this longitudinal, family study with healthy controls was to explore whether VM dysfunction represents a neurocognitive endophenotype of BD.

METHODS

Assessment of VM by Rey-Osterrieth Complex Figure Test (ROCF) was carried out on a sample of 317 subjects, including 140 patients with BD, 60 unaffected first-degree relatives (BD-Rel), and 117 genetically-unrelated healthy controls (HC), on three occasions over a 5-year period (T1, T2, and T3). BD-Rel group scores were analyzed only at T1 and T2.

RESULTS

Performance of BD patients was significantly worse than the HC group (p < 0.01). Performance of BD-Rel was also significantly different from HC scores at T1 (p < 0.01) and T2 (p = 0.05), and showed an intermediate profile between the BD and HC groups. Only among BD patients, there were significant differences according to sex, with females performing worse than males (p = 0.03). Regarding other variables, education represented significant differences only in average scores of BD-Rel group (p = 0.01).

LIMITATIONS

Important attrition in BD-Rel group over time was detected, which precluded analysis at T3.

CONCLUSIONS

BD patients show significant deficits in VM that remain stable over time, even after controlling sociodemographic and clinical variables. Unaffected relatives also show stable deficits in VM. Accordingly, the deficit in VM could be considered a potential endophenotype of BD, which in turn may be useful as a predictor of the evolution of the disease. Further studies are needed to confirm these findings.

Resting-state fMRI signals in offspring of parents with bipolar disorder at the high-risk and ultra-high-risk stages and their relations with cognitive function

BACKGROUND

Bipolar disorder (BD) has been associated with dysfunctional resting-state brain functioning. However, it is still not known whether the aberrant functioning occurs and predict cognitive functioning before illness onset.

AIMS

We examined the resting-state regional and network dysfunctioning, and their correlates with neurocognitive performance, in the high-risk (HR) and ultra-high-risk (UHR) stages of bipolar disorder.

METHODS

Using amplitude of low-frequency fluctuations (ALFF), region homogeneity (ReHo) and hypothesis-driven region-of-interest (ROI)-based connectivity, we examined resting-state fMRI data of 8- to 25-year-old healthy offspring (HR, n = 28) and offspring with subthreshold syndromes (UHR, n = 22) of a BD parent, and age-matched healthy controls without any personal or family psychopathology (HC, n = 46). Participants' neurocognitive profiles were assessed using the MATRICS Consensus Cognitive Battery (MCCB).

RESULTS

ALFF signals in the left putamen and right rolandic operculum were lower in the HR group compared to the HC group. In contrast, ALFF signals were increased in the UHR group in the right middle pars orbitalis of the inferior frontal gyrus, right calcarine sulcus and right cerebellum. Connectivities between the right amygdala and left inferior temporal gyrus, between the left hippocampus and inferior occipital gyrus, and between the left hippocampus and middle pars orbitalis gyrus were decreased in the HR group compared to the HC group. In UHR versus HC group, connectivity between the right amygdala and the left hippocampus and left insula was increased, and connectivity between the left hippocampus and the left insula and the cerebellum was also increased. Among cognitive measures, processing speed was positively correlated with ALFF signals in the left putamen in the HR offspring. In the UHR offspring, processing speed, attention, and verbal learning/memory were positively correlated with the functional connectivity between the left hippocampus and cerebellum.

CONCLUSIONS

Offspring of parents with BD in the HR and UHR stages show largely non-overlapping patterns of atypical resting-state signals and functional connectivity that predicted cognitive functioning, possibly reflecting inherited abnormalities and/or complimentary reactions.

Biochemical abnormalities in basal ganglia and executive dysfunction in acute- and euthymic-episode patients with bipolar disorder: A proton magnetic resonance spectroscopy study

BACKGROUND

Recent studies found abnormal biochemical metabolism and executive cognitive deficits in acute bipolar disorder (BD). However, the evidence concerning in euthymic BD is limited. Thus, a comparison between acute and euthymic BD is conductive to better understanding the association between cognition and the outcome of neuroimaging. This study sought to investigate the relationship between the executive function and the biochemical metabolism in acute- and euthymic-episode BD patients and delineate the prominent endophenotype of BD.

METHODS

Three groups of participants were recruited in this study: 30 BD patients with an acute depressive episode, 22 euthymic BD patients, and 31 healthy controls. All participants were interviewed using the Structured Clinical Interview for DSM-IV, and underwent two-dimensional multivoxel proton magnetic resonance spectroscopy (1H-MRS) to obtain the bilateral metabolite levels in the lenticular nucleus of basal ganglia(BG). The ratios of N-acetylaspartate (NAA)/creatine (Cr) and Choline-containing compounds (Cho) /Cr ratios were calculated. Executive function was assessed by using the Wisconsin Card Sorting Test (WCST) and Trail Making Test, Part-B(TMT-B).

RESULTS

The comparison of biochemical changes showed that the NAA/Cr ratios in bilateral lenticular nucleus in both acute and euthymic BD patients was significantly lower than that in healthy controls at a confidence level of p<0.05. In the comparison of executive function, both acute and euthymic BD patients showed significantly decreased numbers of categories completed, and increased numbers of total errors, perseverative and noperseverative errors, and TMT-B uptake compared to the healthy controls at a confidence level of p<0.05. There were no significant differences between the acute BD and euthymic BD groups in the biochemical metabolite ratios and executive function. We found that the NAA/Cr ratio in the left in BG in the acute -episode BD patients was positively correlated with the number of categories completed, whereas it was negatively correlated with the total errors and TMT-B uptake. There was no correlation between the NAA/Cr and Cho/Cr ratios in the bilateral BG and the scores of SWCT and TMT-B in euthymic-episode BD patients.

LIMITATION

The sample size was relatively small and not all the euthymic-episode patients are the ones with an acute episode.

CONCLUSIONS

Our findings suggest that biochemical abnormalities in the lenticular nucleus and the executive dysfunction may occur early in the course of BD, and persist during remission, and are the most likely markers of endophenotypes of BD. The dysfunction of the neuronal function in the lenticular nucleus may be correlated with the cold dysfunction in patients with acute BD.

CACNA1C polymorphisms Impact Cognitive Recovery in Patients with Bipolar Disorder in a Six-week Open-label Trial

Cognitive impairments in bipolar patients deteriorate as the disorder progresses. Little is known about whether genetic risks impact cognitive recovery during the course from depression to remission. In this six-week open-label trial, we shed light on the impacts of six single nucleotide polymorphisms (SNPs) in the calcium voltage-gated channel subunit alpha1 C (CACNA1C) gene on cognitive recovery in 192 bipolar patients suffering a major depressive episode (MDE). The primary outcome measures were changes in a battery of neuropsychological tests following 6-week treatment. Carriers with rs10466907 GT genotype did not significantly improve their executive function total scores on the Wisconsin Card Sorting Test after six weeks of treatment compared to the TT genotypes (β = −0.944, 95% Confidence Interval (CI) = −1.482–−0.405). Moreover, during a MDE carriers with rs58619945 GG and GA genotypes performed significantly worse than those with AA genotype on the categories completed (p = 0.013 and p = 0.001), total errors (p = 0.039 and p = 0.009), and random errors (p = 0.055 and p = 0.014, respectively). Our data suggest that the tested CACNA1C SNPs may have impacts on cognitive recovery from depression.

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.

Neurocognitive functioning in euthymic patients with bipolar disorder and unaffected relatives: A review of the literature

BACKGROUND

Neurocognitive deficits are present in bipolar disorder (BD) patients and their unaffected (nonbipolar) relatives, but it is not clear which domains are most often impaired and the extent of the impairment resulting from shared genetic factors. In this literature review, we address these issues and identify specific neurocognitive tasks most sensitive to cognitive deficits in patients and unaffected relatives.

METHOD

We conducted a systematic review in Web of Science, PubMed/Medline and PsycINFO databases.

RESULTS

Fifty-one articles assessing cognitive functioning in BD patients (23 studies) and unaffected relatives (28 studies) were examined. Patients and, less so, relatives show impairments in attention, processing speed, verbal learning/memory, and verbal fluency.

CONCLUSION

Studies were more likely to find impairment in patients than relatives, suggesting that some neurocognitive deficits may be a result of the illness itself and/or its treatment. However, small sample sizes, differences among relatives studied (e.g., relatedness, diagnostic status, age), and differences in assessment instruments may contribute to inconsistencies in reported neurocognitive performance among relatives. Additional studies addressing these issues are needed.

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.

Die Bedeutung kognitiver Beeinträchtigungen bei depressiven Patienten

Zusammenfassung. Beeinträchtigungen der Exekutivfunktionen, der Aufmerksamkeit und des Gedächtnisses sind einige der häufigsten und hartnäckigsten Symptome depressiver Störungen. Bisher konnte allerdings kein eindeutiges Profil dieser Defizite identifiziert werden, wahrscheinlich auch deshalb, weil die Defizite von verschiedenen klinischen und demografischen Faktoren, wie dem Depressionssubtypus, Grübeln, Komorbiditäten und Alter beeinflusst werden. Die kognitiven Beeinträchtigungen verbessern sich mit der Remission der Störung, häufig findet jedoch keine vollständige Rückbildung statt. Sie sind klinisch sehr relevant und gehen einher mit Suizidalität, reduzierten Therapieeffekten und negativen Auswirkungen auf Alltagsaktivitäten. Aus diesen Gründen ergibt sich für betroffene Patienten die Notwendigkeit einer neuropsychologischen Behandlung. Erste Ergebnisse lassen hoffen, dass die kognitiven Beeinträchtigungen mithilfe neuropsychologischer Therapie, Achtsamkeitstraining, psychopharmakologischer Therapie und weiteren neurobiologischen Behandlungen, wie z. B. der repetitiven transkraniellen Magnetstimulation, erfolgreich behandelt werden können.

DNA methylation in a Scottish family multiply affected by bipolar disorder and major depressive disorder

BACKGROUND

Bipolar disorder (BD) is a severe, familial psychiatric condition. Progress in understanding the aetiology of BD has been hampered by substantial phenotypic and genetic heterogeneity. We sought to mitigate these confounders by studying a multi-generational family multiply affected by BD and major depressive disorder (MDD), who carry an illness-linked haplotype on chromosome 4p. Within a family, aetiological heterogeneity is likely to be reduced, thus conferring greater power to detect illness-related changes. As accumulating evidence suggests that altered DNA methylation confers risk for BD and MDD, we compared genome-wide methylation between (i) affected carriers of the linked haplotype (ALH) and married-in controls (MIs), (ii) well unaffected haplotype carriers (ULH) and MI, (iii) ALH and ULH and (iv) all haplotype carriers (LH) and MI.

RESULTS

Nominally significant differences in DNA methylation were observed in all comparisons, with differences withstanding correction for multiple testing when the ALH or LH group was compared to the MIs. In both comparisons, we observed increased methylation at a locus in FANCI, which was accompanied by increased FANCI expression in the ALH group. FANCI is part of the Fanconi anaemia complementation (FANC) gene family, which are mutated in Fanconi anaemia and participate in DNA repair. Interestingly, several FANC genes have been implicated in psychiatric disorders. Regional analyses of methylation differences identified loci implicated in psychiatric illness by genome-wide association studies, including CACNB2 and the major histocompatibility complex. Gene ontology analysis revealed enrichment for methylation differences in neurologically relevant genes.

CONCLUSIONS

Our results highlight altered DNA methylation as a potential mechanism by which the linked haplotype might confer risk for mood disorders. Differences in the phenotypic outcome of haplotype carriers might, in part, arise from additional changes in DNA methylation that converge on neurologically important pathways. Further work is required to investigate the underlying mechanisms and functional consequences of the observed differences in methylation.

A Multi-Dimensional and Integrative Approach to Examining the High-Risk and Ultra-High-Risk Stages of Bipolar Disorder

BACKGROUND

Validating the high-risk (HR) and ultra-high-risk (UHR) stages of bipolar disorder (BP) may help enable early intervention strategies.

METHODS

We followed up with 44 offspring of parents with BP, subdividing into the HR and UHR categories. The offspring were aged 8-28 years and were free of any current DSM-IV diagnoses. Our multilevel, integrative approach encompassed gray matter (GM) volumes, brain network connectivity, neuropsychological performance, and clinical outcomes.

FINDINGS

Compared with the healthy controls (HCs) (n = 33), the HR offspring (n = 26) showed GM volume reductions in the right orbitofrontal cortex. Compared with the HR offspring, the UHR offspring (n = 18) exhibited increased GM volumes in four regions. Both the HR and UHR offspring displayed abnormalities in the inferior occipital cortex regarding the measures of degree and centrality, reflecting the connections and roles of the region, respectively. In the UHR versus the HR offspring, the UHR offspring exhibited upwards-shifted small world topologies that reflect high clustering and efficiency in the brain networks. Compared with the HCs, the UHR offspring had significantly lower assortativity, which was suggestive of vulnerability. Finally, processing speed, visual-spatial, and general function were impaired in the UHR offspring but not in the HR offspring.

INTERPRETATION

The abnormalities observed in the HR offspring appear to be inherited, whereas those associated with the UHR offspring represent stage-specific changes predisposing them to developing the disorder.

Neuropsychological performance of patients with soft bipolar spectrum disorders

OBJECTIVES

There is much evidence that shows that a substantial number of individuals with DSM-IV-defined unipolar depression (UP) manifest hypomanic sub-syndrome and bipolar diathesis. Other definitions have conceptualized the term soft bipolar spectrum (SBP) for these individuals. Little is known about the cognitive profiles of individuals with SBP. We hypothesized that they are representative of individuals with bipolar II disorder and are different from that of 'strict' UP.

METHODS

Consecutive referrals suffering major depressive episodes were categorically assigned to groups of either bipolar I disorder (n = 98), bipolar II disorder (n = 138), or UP (n = 300). Based on the SBP criteria by Akiskal and Pinto (17), patients with UP were subdivided into 81 SBP and 219 strict UP. We administered self- and clinician-administered scales to evaluate affective temperaments, and neuropsychological tests to assess seven cognitive domains.

RESULTS

Patients with SBP performed significantly better than strict UP patients in the domains of processing speed (p = 0.002), visual-spatial memory (p = 0.017), and verbal working memory (p = 0.017). Compared to patients with bipolar I disorder, patients with SBP were significantly better in set shifting (p < 0.001) and visual-spatial memory (p = 0.042). Patients with SBP performed similarly to patients with bipolar II disorder in all of the cognitive domains tested (p > 0.05). There was a group × cognitive domain interaction effect between bipolar I disorder, bipolar II disorder, SBP, and strict UP groups [Pillai's F = 2.231, df = (18,1437), p = 0.002].

CONCLUSIONS

Our data suggest that patients with SBP differ from patients with UP not only in external validators (e.g., family history of bipolar disorder) and hypomanic symptoms, but also in neuropsychological performance and that the profiles of cognitive functioning were different across bipolar I disorder and 'bipolar II spectrum' that subsumes bipolar II disorder and SBP.

Neural correlates of generation and inhibition of verbal association patterns in mood disorders

OBJECTIVES

Thought disorders such as rumination or flight of ideas are frequent in patients with mood disorders, and not systematically linked to mood state. These symptoms point to anomalies in cognitive processes mediating the generation and control of thoughts; for example, associative thinking and inhibition. However, their neural substrates are not known.

METHOD

To obtain an ecological measure of neural processes underlying the generation and suppression of spontaneous thoughts, we designed a free word association task during fMRI allowing us to explore verbal associative patterns in patients with mood disorders and matched controls. Participants were presented with emotionally negative, positive or neutral words, and asked to produce two words either related or unrelated to these stimuli.

RESULTS

Relative to controls, patients produced a reverse pattern of answer typicality for the related vs unrelated conditions. Controls activated larger semantic and executive control networks, as well as basal ganglia, precuneus and middle frontal gyrus. Unlike controls, patients activated fusiform gyrus, parahippocampal gyrus and medial prefrontal cortex for emotional stimuli.

CONCLUSIONS

Mood disorder patients are impaired in automated associative processes, but prone to produce more unique/personal associations through activation of memory and self-related areas.

A genome-wide supported psychiatric risk variant in NCAN influences brain function and cognitive performance in healthy subjects

The A allele of the single nucleotide polymorphism (SNP) rs1064395 in the NCAN gene has recently been identified as a susceptibility factor for bipolar disorder and schizophrenia. NCAN encodes neurocan, a brain-specific chondroitin sulfate proteoglycan that is thought to influence neuronal adhesion and migration. Several lines of research suggest an impact of NCAN on neurocognitive functioning. In the present study, we investigated the effects of rs1064395 genotype on neural processing and cognitive performance in healthy subjects. Brain activity was measured with functional magnetic resonance imaging (fMRI) during an overt semantic verbal fluency task in 110 healthy subjects who were genotyped for the NCAN SNP rs1064395. Participants additionally underwent comprehensive neuropsychological testing. Whole brain analyses revealed that NCAN risk status, defined as AA or AG genotype, was associated with a lack of task-related deactivation in a large left lateral temporal cluster extending from the middle temporal gyrus to the temporal pole. Regarding neuropsychological measures, risk allele carriers demonstrated poorer immediate and delayed verbal memory performance when compared to subjects with GG genotype. Better verbal memory performance was significantly associated with greater deactivation of the left temporal cluster during the fMRI task in subjects with GG genotype. The current data demonstrate that common genetic variation in NCAN influences both neural processing and cognitive performance in healthy subjects. Our study provides new evidence for a specific genetic influence on human brain function.

Aging changes and medical complexity in late-life bipolar disorder: emerging research findings that may help advance care

Demographic trends globally point in the direction of increasing numbers of older people with serious and chronic mental disorders, such as bipolar disorder (BD). While there has been growing sophistication and understanding in treatments for BD generally, data specific to older people with BD are limited. Recent reviews, secondary analyses and some new research confirm complexity and aging-related issues relevant to later-life BD. Confounding variables that must be considered when studying older BD individuals include clinical heterogeneity, medical comorbidity, cognitive impairment and concomitant psychotropic medication. This article will review current and emerging data on aging- and disease-related issues that complicate assessment and treatment of older individuals with BD. We will discuss common comorbid medical conditions that affect BD elders, how aging may affect cognition and treatment, including the effects of lithium and other psychotropic drugs on the aging brain, and recent research using neuroimaging techniques that may shed light on understanding the mechanisms of illness progression and on treatment response. Finally, we will discuss implications for future work in geriatric BD.