Cognitive Impairment In Treatment-Naïve Bipolar II and Unipolar Depression

Status of Type II vs. Type I Bipolar Disorder: Systematic Review with Meta-Analyses

LEARNING OBJECTIVES AFTER PARTICIPATING IN THIS CME ACTIVITY, THE PSYCHIATRIST SHOULD BE BETTER ABLE TO

• Analyze and compare the different bipolar disorder (BD) types.• Identify markers that distinguish BD types and explain how the DSM-IV defines the disorder.

ABSTRACT

Since the status of type II bipolar disorder (BD2) as a separate and distinct form of bipolar disorder (BD) remains controversial, we reviewed studies that directly compare BD2 to type I bipolar disorder (BD1). Systematic literature searching yielded 36 reports with head-to-head comparisons involving 52,631 BD1 and 37,363 BD2 patients (total N = 89,994) observed for 14.6 years, regarding 21 factors (with 12 reports/factor). BD2 subjects had significantly more additional psychiatric diagnoses, depressions/year, rapid cycling, family psychiatric history, female sex, and antidepressant treatment, but less treatment with lithium or antipsychotics, fewer hospitalizations or psychotic features, and lower unemployment rates than BD1 subjects. However, the diagnostic groups did not differ significantly in education, onset age, marital status, [hypo]manias/year, risk of suicide attempts, substance use disorders, medical comorbidities, or access to psychotherapy. Heterogeneity in reported comparisons of BD2 and BD1 limits the firmness of some observations, but study findings indicate that the BD types differ substantially by several descriptive and clinical measures and that BD2 remains diagnostically stable over many years. We conclude that BD2 requires better clinical recognition and significantly more research aimed at optimizing its treatment.

Mitochondrial dysfunction in psychiatric disorders

Psychiatric disorders are a heterogeneous group of mental disorders with abnormal mental or behavioral patterns, which severely distress or disable affected individuals and can have a grave socioeconomic burden. Growing evidence indicates that mitochondrial function plays an important role in developing psychiatric disorders. This review discusses the neuropsychiatric consequences of mitochondrial abnormalities in both animal models and patients. We also discuss recent studies associated with compromised mitochondrial function in various psychiatric disorders, such as schizophrenia (SCZ), major depressive disorder (MD), and bipolar disorders (BD). These studies employ various approaches including postmortem studies, imaging studies, genetic studies, and induced pluripotent stem cells (iPSCs) studies. We also summarize the evidence from animal models and clinical trials to support mitochondrial function as a potential therapeutic target to treat various psychiatric disorders. This review will contribute to furthering our understanding of the metabolic etiology of various psychiatric disorders, and help guide the development of optimal therapies.

Neurocognitive deficits in depression: a systematic review of cognitive impairment in the acute and remitted state

Previous research suggests a broad range of deficits in major depressive disorder. Our goal was to update the current assumptions and investigate the extent of cognitive impairment in depression in the acute and remitted state. A systematic review of the existing literature between 2009 and 2019 assessing the risk of bias within the included studies was performed. Of the 42 articles reviewed, an unclear risk of bias was shown overall. The risk of bias mainly concerned the sample selection, inadequate remedial measures, as well as the lack of blinding the assessors. In the acute phase, we found strong support for impairment in processing speed, learning, and memory. Follow-up studies and direct comparisons revealed less pronounced deficits in remission, however, deficits were still present in attention, learning and memory, and working memory. A positive correlation between the number of episodes and cognitive deficits as well as depression severity and cognitive deficits was reported. The results also demonstrate a resemblance between the cognitive profiles in bipolar disorder and depression. Comparisons of depression with schizophrenia led to unclear results, at times suggesting an overlap in cognitive performance. The main findings support the global deficit hypothesis and align with results from prior meta-analyses and reviews. Recommendations for future research are also presented.

The prevalence and characteristics of MCCB cognitive impairment in unmedicated patients with bipolar II depression and major depressive disorder

BACKGROUND

Cognitive impairment has been acknowledged as a core clinical manifestation of bipolar disorder (BD) as well as major depressive disorder (MDD). Determining the prevalence and characteristics of cognitive impairment is important for clinical interventions. This study investigated the prevalence and characteristics of cognitive impairment based on the Measurement and Treatment Research to Improve Cognition Schizophrenia Consensus Cognitive Battery (MCCB) in both BD and MDD.

METHOD

One hundred and forty-nine BD II depression, 147 MDD, and 124 demographically matched healthy controls (HC) underwent MCCB cognitive assessment. The prevalence of MCCB cognitive impairment and group difference comparisons were performed. Additionally, association analysis was performed to investigate the relationship between cognitive performance and clinical variables.

RESULTS

Compared to the HC group, both BD II depression and MDD groups had a significantly reduced performance for all MCCB cognitive domains (all p < 0.05). The numerical scores for visual learning were lower in the BD II depression group compared to the MDD group. 32.89% of the BD II depression patients had clinically significant impairment (>1.5 SD below the normal mean) in two or more MCCB domains compared to 23.13% for MDD patients.

CONCLUSIONS

A high percent of patients in the BD II depression and MDD group exhibited MCCB cognitive impairments with clinical significance. Cognitive impairments were more common in BD II depression patients compared to MDD patients, particularly for visual learning. These findings suggest that clinicians should be aware of the severe cognitive impairment in mood disorders and establish effective cognitive screening and intervention strategies.

Behavior Rating Inventory of Executive Function - adult version (BRIEF-A) in Iranian University students: Factor structure and relationship to depressive symptom severity

Major depressive disorder is the most common psychiatric illness in Iran, and depression is common among university students in the country. The presence of depression is frequently associated with problems in executive functioning. The Behavior Rating Inventory of Executive Function-Adult Version (BRIEF-A) is a questionnaire measure designed to assess executive functioning in everyday life in clinical and non-clinical populations. Currently, there is limited empirical validation of the measure for use in Iran. This study evaluated the psychometric properties of a Persian-language BRIEF-A in a sample of Iranian university students (n = 300). The factor structure of the BRIEF-A was examined via a confirmatory factor analysis. We also evaluated whether BRIEF-A scores differed among university students varying in severity of depressive symptoms (Minimal, Mild, Moderate, Severe) as measured by the Beck Depression Inventory - II. Results indicated that a two-factor model structure best fit the data for the BRIEF-A. Acceptable internal consistency was also observed. Furthermore, poorer subjective executive functioning was endorsed by the three depressive subgroups relative to the Minimal symptoms group. Together, these findings support a two-factor model for the Persian translation of the BRIEF-A, and indicate that more severe depressive symptoms in Iranian university students is associated with worse subjective executive functioning.

Neuropsychological aspects of bipolar disorder

Bipolar disorder (BD) is a chronic condition with serious consequences on the health and functionality of patients who suffer from it, with a high heritability and segregation, and aprevalence of between 1% and 2%. Neuropsychological deficits have been implicated as a very important issue related to BD prognosis, so a review was conducted of these deficits, the related factors and their functional consequences. It has been determined that the presence of neuropsychological deficits can vary in patients with BD according to their mood state, with a great influence of depressive symptoms on the cognitive variability of patients with respect to the general population and differences with respect to patients in the manic phase. In euthymic patients, the most affected cognitive domains are those of memory, attention, and executive function, associated with a more severe disease, sociodemographic vulnerability factors, and stable over time. A relationship has been found between poor cognitive performance, especially executive dysfunction, and objective functional deficit. Furthermore, cognitive differences have been outlined between BD and other serious mental illnesses that are described in this review.

Effect and neural mechanisms of the transcutaneous vagus nerve stimulation for relapse prevention in patients with remitted major depressive disorder: protocol for a longitudinal study

INTRODUCTION

After the first episode, patients with remitted major depressive disorder (MDD) have a 60% chance of experiencing a second episode. There are currently no accepted, effective methods to prevent the recurrence of MDD in remission. Transcutaneous vagus nerve stimulation (taVNS) is a non-invasive, safe and economical approach based on the efficacy of VNS in improving clinical depression symptoms. This clinical trial will study the efficacy of taVNS in preventing MDD relapse and investigate the underlying mechanisms of this.

METHODS AND ANALYSIS

We will conduct a multicentre, randomised, patient-blinded and evaluators double-blinded trial. We will randomise 90 eligible participants with recurrent MDD in remission in a 1:1 ratio into a real or sham taVNS group. All participants will be given six biopsychosocial assessments: proinflammatory cytokines, serum monoamine neurotransmitters, cognition, affective neuropsychology, multimodal neuroimaging and endocrinology. After the baseline measurements, all participants will be given corresponding interference for 6 months and then complete a 1-year follow-up. The assessments will be performed three times: at baseline, post-treatment and at the end of 1-year follow-up (except for multimodal MRI scanning, which will be conducted at the first two assessments only). Change in 17-item Hamilton Depression Rating Scale scores for MDD is the primary outcome parameter.

ETHICS AND DISSEMINATION

The study protocol was approved by the Medical Ethical Committee of Beijing Hospital of Traditional Chinese Medicine on 18 January 2019 (2018BL-076). The trial results will be published in peer-reviewed journals and at conferences.

TRIAL REGISTRATION NUMBER

ChiCTR1900022618.

Cognitive Impairment and Neurocognitive Profiles in Major Depression-A Clinical Perspective

Increasingly, studies have investigated cognitive functioning from the perspective of acute state- to remitted phases of Major Depressive Disorder (MDD). Some cognitive deficits observed in the symptomatic phase persist in remission as traits or scars. The etiological origin and clinical consequences of the neurocognitive profiles reported in the literature are still unclear and may vary across populations. Deficits are suspected to influence the association between MDD and neurodegenerative disorders and could thus be of particular clinical consequence. The aim of this review is to describe the clinical neuropsychological profile in MDD and how it is related to research during the past decade on cognitive deficits in MDD from a state, trait, and scar perspective. This review, with a clinical perspective, investigates research from the past decade regarding cognitive functioning in MDD in a long-term perspective. We focus on the clinical manifestation of deficits, and the potential neurodegenerative consequences of the neurocognitive profile in MDD. Searches in Medline, PsycINFO and Embase were conducted targeting articles published between 2010 and 2020. Examination of the evidence for long-lasting neurocognitive deficits in major depression within the cognitive domains of Memory, Executive Functions, Attention, and Processing Speed was conducted and was interpreted in the context of the State, Scar and Trait hypotheses. Defining the neurocognitive profiles in MDD will have consequences for personalized evaluation and treatment of residual cognitive symptoms, and etiological understanding of mood disorders, and treatments could potentially reduce or delay the development of neurodegenerative disorders.

Cognitive Profile and Relationship with Quality of Life and Psychosocial Functioning in Mood Disorders

BACKGROUND

Comparisons between healthy controls (HCs) and individuals with mood disorders have shown more cognitive dysfunction among the latter group, in particular in bipolar disorder (BD). This study aimed to characterize the pattern of cognitive function of BD and major depressive disorder (MDD) and compare them to HC using the (CogState Research Battery) CSRB™.

METHOD

Participants were tested, comprising the following domains: processing speed, attention, working memory, visual memory, executive functions, and verbal memory. Quality of life and functionality were also assessed. Multiple linear regression models were performed to examine the effect of demographic characteristics and functionality on cognitive outcomes separately for BD and MDD.

RESULTS

Ninety individuals participated in the study, of which 32 had BD, 30 had MDD, and 28 were HC. Differences were found between both BD and MDD and HC for the composite cognitive score, with significant differences between BD and HC (Diff = -5.5, 95% CI = [-9.5, -1.5], p = 0.005), and MDD and HC (Diff = -4.6, 95% CI = [-8.6, -0.5], p = 0.025). There were overall significant differences in five cognitive domains: processing speed (p = 0.001 and p = 0.004), attention (p = 0.002), working memory (p = 0.02), visual memory (p = 0.021), and verbal memory (p = 0.007). BD also presented worse performance than both MDD and HC, and MDD presented better performance than BD but worse than HC in quality of life and functionality. Multiple linear regression models were significative for education (p < 0.001) and age (p = 0.004) for BD and education (p < 0.001) for MDD.

CONCLUSION

In general, cognition is more affected in BD than MDD, which could be associated with functional and quality of life impairment.

Association of altered thyroid hormones and neurometabolism to cognitive dysfunction in unmedicated bipolar II depression

BACKGROUND

The underlying mechanism of cognitive impairment in bipolar II depression (BD II) remains unclear. Studies show disturbances of the hypothalamus-pituitary-thyroid (HPT) axis are suspected of correlating to brain neurometabolic alterations and cognitive deficits in psychiatric disorders. While, the nature of their inter-relationships in BD II depression remain enigmatic.

METHODS

106 patients with unmedicated BD II depression and 100 healthy controls underwent cognitive function assessment using Trail Making Test, Part-A (TMT-A), Digit Symbol Substitution Test (DSST), and Semantic Verbal Fluency testing (SVF). Of those, 69 patients and 53 healthy controls had serum thyroid hormone levels measured including free tri-iodothyronine (FT3), total tri-iodothyronine (TT3), free thyroxin (FT4), total thyroxin (TT4) and thyroid-stimulating hormone (TSH). Additionally, 79 of the patients and 76 of the healthy controls underwent proton magnetic resonance spectroscopy (H-MRS) to obtain ratios of N-acetyl aspartate to creatine (NAA/Cr) and choline-containing compounds to creatine (Cho/Cr) in the prefrontal cortex (PFC), anterior cingulate cortex (ACC) and thalamus. Finally, association and multiple regression analysis were conducted to investigate their inter-relationships.

RESULTS

Patients with BD II depression showed significantly lower DSST and verbal fluency scores and longer completion time of TMT-A than did healthy controls. The FT3, TT3, and TSH levels of the BD cohort significantly decreased, while their FT4 levels increased. We also found significantly lower NAA/Cr ratios in the PFC and higher NAA/Cr ratios in the left thalamus of patients with BD II depression than in healthy controls. Furthermore, association analysis showed that increased FT4 negatively correlated to DSST and SVF, while increased FT4 correlation significantly with increasing TSH and DSST. Multiple regression analyses revealed relationships between TSH and NAA in the left PFC and the left thalamus, while correlating to SVF testing within the BD II depression cohort.

CONCLUSIONS

Our results demonstrate coinciding thyroid hormone abnormalities, cognitive dysfunction, and neurometabolic alterations of the PFC-thalamic circuitry occur in an early course of BD II depression. Further understanding of the interaction between thyroid-stimulating hormone and NAA/Cr of PFC-thalamic circuitry may shed light on the etiology of associated cognitive impairment.

White matter integrity in young medication-naïve bipolar II depressed adults

It is unknown if young medication-naïve bipolar II (BPII) depressed patients have increased white matter (WM) disruptions. 27 each of young (average 23 years) and treatment-naïve BPII depressed, unipolar depressed (UD) patients and age–sex–education matched healthy controls (HC) underwent 3 T MRIs with diffusion tensor imaging. Diagnostic ratings included Structured Clinical Interview for DSM Disorders (SCID), Montgomery-Åsberg Depression Rating Scale (MADRS), Young Mania Rating Scale (YMRS) and Hamilton Anxiety Rating Scale (HAM-A). Patients were clinically depressed (MADRS-BPII: 26.15 [SD9.25], UD: 25.56 [5.24], p = 0.86). Compared to UD, BPII had increased family bipolarity (BPII 13.6% vs UD 2.5%, p = 0.01, φc = 0.28), hypomanic symptoms (YMRS-BPII: 4.22 [4.24], UD: 1.33 [2], p = 0.02, d = 0.87), lifetime number of depressive episodes (BPII: 2.37 [1.23], UD: 1.44 [0.75], p = 0.02, d = 0.91), lifetime and current-year number of episodes (lifetime BPII: 50.85 [95.47], UD: 1.7 [1.03]; current-year BPII: 9.93 [16.29], UD: 1.11 [0.32], ps = 0.04, ds = 0.73–0.77) and longer illness duration (BPII: 4.96 years [3.96], UD: 2.99 [3.33], p = 0.15, d = 0.54). BPII showed no increased WM disruptions vs UD or HC in any of the 15 a priori WM tracts. UD had lower right superior longitudinal fasciculus (SLF) (temporal) axial diffusivity (AD) (1.14 vs 1.17 (BPII), 1.16 (HC); F = 6.93, 95% CI of\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${F}_{B}$$\end{document}FB: 0.00073, 5.22, ηp² = 0.15). Principal component analysis followed by exploratory linear discriminant analysis showed that increased R-SLF (temporal) AD, YMRS and family bipolarity distinguished BPII from UD (81.5% sensitivity, 85.2% specificity) independent of episode number and frequency. Young, medication-naïve adults with BPII depression did not show the WM disruptions distinguishing more chronically ill BP patients from UD. These WM disruptions may therefore be partly attributable to illness chronicity. Longitudinal studies should examine the trajectory of WM changes in BPII and UD and predictive validity of these baseline clinical and imaging parameters.

Performances on individual neurocognitive tests by people experiencing a current major depression episode: A systematic review and meta-analysis

BACKGROUND AND PURPOSES

Previous meta-analyses on neurocognitive test performances in depression have provided effect sizes for cognitive domains. Most domain effect sizes have medium to high variance heterogeneity. Restriction to each test performance could reduce variance and clarify differing test effect sizes. This systematic review and meta-analysis were done to 1. provide effect sizes for cognitive performances (test, subtest, or multiple measures within tests), and 2. investigate age as an effect modifier.

METHODS

Inclusion criteria were: 1. active major depression episode (MD), 2. a control group, 3 reported means and standard deviations, 4. non-computerized tests previously studied at least 3 times. Meta-analyses were performed using Cochrane Review Manager. Age under versus over 45 was investigated as an effect moderator.

RESULTS

Twenty-seven studies met criteria. MD patients performed significantly poorer on 16 of 16 neurocognitive measures (random effects d = -0.47 to -0.92 across tests). Variance was heterogeneous for 11 of 16 measures. Differences between cognitive measures were largely absent based on overlapping 95% confidence intervals. Effect sizes did not differ under versus over 45 years.

LIMITATIONS

Bias risk assessment showed limited control for subject selection, comparability of depressed and control groups, pre-morbid intelligence, drug treatment, and effort in testing.

CONCLUSIONS

The depression - cognition effect was in the moderate to large range regardless of test type. Variance heterogeneity was substantial despite exclusion of inactive depression and the absence of test pooling. The size of the depression - cognition effect was not a function of age.

Duration of untreated illness and depression severity are associated with cognitive impairment in mood disorders

Introduction: In this study we estimated the rate and the trajectory of cognitive impairment in a naturalistic sample of outpatients with major depressive disorder (MDD) and bipolar disorder (BD) and its correlation with different variables.Materials and methods: An overall sample of 109 outpatients with MDD or BD was assessed for multiple clinical variables, including duration of untreated illness (DUI), and tested using the Montreal Cognitive Assessment (MoCA) during Major Depressive Episodes (MDE) and after remission. Correlations between MoCA scores and the clinical variables were then computed.Results: About 50% of patients with MDD and BD showed mild cognitive impairment during MDE. Improvement of cognitive function between depression and remission was significant, even though residual symptoms were observed especially in the most impaired patients. Of note, cognitive performance during depression was negatively associated with depression severity and DUI.Discussion: Present findings confirm available evidence about patterns of cognitive impairment in mood disorders, in terms of prevalence and persistence beyond remission in most severe cases. Moreover, a longer DUI was associated with worse cognitive performance during depression, and consequently with poorer outcome, underlining the importance of prompt treatment of these disorders also in light of a cognitive perspective.KeypointsAlthough distinct entities, unipolar and bipolar depression determine similar patterns of cognitive impairment in terms of severity and types of altered domains.Depression (but not anxiety) severity is associated with cognitive performance in depression.Prolonged duration of untreated illness is associated with more severe cognitive impairment during depression, particularly but not specifically in bipolar disorder.

Using network analysis to explore cognitive domains in patients with unipolar versus bipolar depression: a prospective naturalistic study

OBJECTIVE

Despite growing evidence in the field of cognitive function in mood disorders, the neurocognitive profiles of patients with unipolar and bipolar depression still need further characterization. In this study, we applied network analysis, hypothesizing this approach could highlight differences between major depressive disorder (MDD) and bipolar disorder (BD) from a cognitive perspective.

METHODS

The cognitive performance of 109 patients (72 unipolar and 37 bipolar depressed outpatients) was assessed through the Montreal Cognitive Assessment (MoCA), and a series of clinical variables were collected. Differences in cognitive performance between MDD and BD patients were tested using non-parametric tests. Moreover, a network graph representing MoCA domains as nodes and Spearman's rho correlation coefficients between the domains as edges was constructed for each group.

RESULTS

The presence of mild cognitive impairment was observed in both MDD and BD patients during depression. No statistical significant difference was found between the two groups in terms of overall cognitive performance and across single domains. Nonetheless, network analytic metrics demonstrated different roles of memory and executive dysfunction in MDD versus BD patients: in particular, MDD network was more densely interconnected than BD network, and memory was the node with the highest betweenness and closeness centrality in MDD, while executive function was more central in BD.

CONCLUSIONS

From a network analytic perspective, memory impairment displays a central role in the cognitive impairment of patients with unipolar depression, whereas executive dysfunction appears to be more central in bipolar depression. Further research is warranted to confirm our results.

Correlation Between Decreased Amygdala Subnuclei Volumes and Impaired Cognitive Functions in Pediatric Bipolar Disorder

BACKGROUND

The amygdala has been proposed to be involved in the pathophysiology of pediatric and adult bipolar disorder (BD). The goal of this structural magnetic resonance imaging (sMRI) study was to investigate the morphometric characteristics of amygdala subnuclei in patients with pediatric bipolar disorder (PBD) compared to healthy controls (HCs). Simultaneously, we examined correlation between amygdala subnuclei volumes and cognitive dysfunction.

MATERIALS AND METHODS

We assessed 40 adolescent outpatients, diagnosed with manic or euthymic PBD according to the DSM-5 criteria for BD and 19 HCs. Cognitive functions were evaluated using a Stroop color-word test (SCWT), trail making test (TMT), visual reproduction immediate recall subtest (VR I), and digit span subtest (DST). Amygdala and its subnuclei structures were automated segmented using FreeSurfer software and the volumes of them were compared between groups and correlation with clinical and cognitive outcomes was conducted.

RESULTS

Manic patients exhibited significantly decreased volumes in the bilateral whole amygdala and its basal nucleus, cortico-amygdaloid transition (CAT), and accessory basal nucleus (ABN) compared with HCs. Euthymic patients had decreased volume in the bilateral ABN and left CAT. In addition, we found significant positive associations between VR I scores and the right whole amygdala and its bilateral basal, right lateral, and ABN volumes in the manic group.

CONCLUSION

These findings support previous reports of smaller amygdala volumes and cognitive dysfunctions in PBD, and further mapping abnormalities to specific amygdala subnuclei. Correlation between basolateral volume and VR I of PBD may expand our understanding of neural abnormalities that could be targeted by treatment.

Combined Measures of Psychomotor and Cognitive Alterations as a Potential Hallmark for Bipolar Depression

OBJECTIVE

The current study aimed to examine whether specific features of psychomotor retardation (PMR) and cognitive functioning established different profiles in unipolar (UD) and bipolar depression (BD).

METHODS

Two groups of age-matched patients with UD (n=54) and BD (n=20) completed the Montgomery-Asberg Depression Rating Scale (MADRS/60), the Montreal Cognitive Assessment (MoCA/30), and the Salpêtrière Retardation Rating Scale (SRRS/60). We analyzed the group effect and then performed intra-group analyses.

RESULTS

The BD patients have higher SRRS score, and lower MoCA score than UD despite no difference on the level of depression between UD and BD. Our results show that PMR can be predicted by the level of depression in UD and by the cognitive alteration and onset of disease in BD.

CONCLUSION

PMR is a relevant marker of depression. Our results highlight the importance of concomitant evaluation of psychomotor and cognitive functions in the distinction of UD and BD symptoms.

Social cognition and interaction training (SCIT) for partially remitted patients with bipolar disorder in China

Bipolar disorder (BD) is associated with functional impairment. Social Cognition and Interaction Training (SCIT) has been shown to be feasible and effective at improving social functioning in patients with schizophrenia. We aimed to explore the association between SCIT and improvements in the clinical symptoms and functioning of partially remitted patients with BD in China. Seventy-four BD patients were randomly assigned to the SCIT and psychoeducation (Control) groups. All subjects participated in group interventions weekly for 8 weeks. Furthermore, the participants were administered the Young Mania Rating Scale (YMRS), the 17-item Hamilton Depression Rating Scale (HDRS-17), the Function Assessment Short Test (FAST) and neurocognitive measures at baseline and after eight weeks. There were no differences in demographics, the HDRS-17, YRMS, and FAST scores or neurocognitive measures between the groups at baseline (p>0.05). The repeated-measures analysis revealed that SCIT resulted in greater improvement in the HDRS, YMRS, and FAST scores (including six domains) (p<0.01) and two neurocognitive measures (p<0.05) compared to psychoeducation. Our findings suggest that SCIT is a feasible and promising intervention for the clinical symptoms and functioning of partially remitted patients with BD. Further longitudinal studies are needed to observe the long-term impact of SCIT on emotional and functional improvement in these patients.

Objective and biological markers in bipolar spectrum presentations

INTRODUCTION

Subthreshold presentations of bipolarity (BSPs) pose a diagnostic conundrum, in terms of whether they should be conceptualized and treated similarly as traditionally defined bipolar disorders (BD). While it has been argued that BSPs are on a pathophysiologic continuum with traditionally defined BDs, there has been limited examination of biological and objective markers in these presentations to validate this assertion. Areas covered: The authors review studies examining genetic, neurobiological, cognitive and peripheral markers in BSPs, encompassing clinical and non-clinical populations with subthreshold hypo/manic symptoms. Results are placed in the context of previously identified markers in traditionally defined BDs. Expert commentary: There have been few studies of objective and biological markers in subthreshold presentations of BD, and results are mixed. While abnormalities in brain structure/functioning, peripheral inflammatory, and cognitive markers have been reported, it is unclear whether these findings are specific to BD or indicative of broad affective pathology. However, some studies suggest that increased sensitivity to reward and positive stimuli are shared between subthreshold and traditionally defined BDs, and may represent a point of departure from unipolar major depression. Further examination of such markers may improve understanding of subthreshold bipolar presentations, and provide guidance in terms of therapeutic strategies.

Can P300 aid in the differential diagnosis of unipolar disorder versus bipolar disorder depression? A meta-analysis of comparative studies

BACKGROUND

It is difficult to distinguish between bipolar disorder (BD) and unipolar disorder (UD) depression. Given the different pattern of cognitive impairments between BD and UD, P300 is potentially useful for the differential diagnosis. This meta-analysis was performed to estimate the extent of difference in P300 in patients with BD versus UD depression.

METHODS

Studies comparing P300 between depressed BD and UD patients with or without healthy controls (HCs) were retrieved from major English and Chinese databases. Studies with BD and UD samples that were comparable in terms of age, gender, and depression severity, were rated as having high quality. Standardized mean differences (SMDs) of P300 latency and amplitude were calculated.

RESULTS

In total, eight studies with a total of 397 depressed BD patients, 390 depressed UD patients, and 497 HCs, were included. Among included studies, six were rated as having good quality and three followed BD (n = 146) and UD (n = 144) patients during remission. BD patients had significantly longer P300 latency than UD patients during major depressive episode [SMD (95%CI): 0.580 (0.309, 0.850)] and remission [SMD (95%CI): 1.583 (1.322, 1.844)]. Compared to HCs, remitted BD patients still had significantly longer P300 latency [SMD (95%CI): 0.857 (0.059, 1.656)] but P300 latency of remitted UD patients had decreased to normal [SMD (95%CI): 0.536 (-0.272, 1.343)].

LIMITATIONS

Sample sizes of depressed and remitted patients with BD and UD of included studies are small.

CONCLUSIONS

P300 latency can be used as an auxiliary diagnostic marker for differentiating BD from UD depression.

Functional connectivity between the thalamus and the primary somatosensory cortex in major depressive disorder: a resting-state fMRI study

BACKGROUND

Studies have confirmed that the thalamus and the primary somatosensory cortex (SI) are associated with cognitive function. These two brain regions are closely related in structure and function. The interactions between SI and the thalamus are of crucial significance for the cognitive process. Patients with major depressive disorder (MDD) have significant cognitive impairment. Based on these observations, we used resting-state functional magnetic resonance imaging (rs-fMRI) to investigate whether there is an abnormality in the SI-thalamic functional connection in MDD. Furthermore, we explored the clinical symptoms related to this abnormality.

METHODS

We included 31 patients with first-episode major depressive disorder and 28 age-, gender-, and education-matched healthy controls (HC). The SI-thalamic functional connectivity was compared between the MDD and HC groups. The correlation analyses were performed between areas with abnormal connectivity and clinical characteristics.

RESULTS

Compared with healthy subjects, the MDD patients had enhanced functional connectivity between the thalamus and SI (p < 0.05, corrected). Brain areas with significantly different levels of connectivity had a negative correlation with the Assessment of Neuropsychological Status total score (r = - 0.383, p = 0.033), delayed memory score (r = - 0.376, p = 0.037) and two-digit continuous operation test score (r = - 0.369, p = 0.041) in MDD patients.

CONCLUSIONS

These results demonstrate that SI-thalamic functional connectivity is abnormal and associated with the core clinical symptoms in MDD. The SI-thalamic functional connectivity functions as a neurobiological feature and potential biomarker for MDD.