Sustained attention and executive functions in euthymic young people with bipolar disorder

Cognitive endophenotypes of bipolar disorder: a meta-analysis of neuropsychological deficits in euthymic patients and their first-degree relatives

BACKGROUND

Our aim was to delineate neuropsychological deficits related to genetic susceptibility, illness process and iatrogenic factors in bipolar disorder (BD).

METHODS

Following an extensive publication search on several databases, meta-analyses were conducted for 18 cognitive variables in studies that compared performances of euthymic BD patients (45 studies; 1423 subjects) or first-degree relatives of BD patients (17 studies; 443 subjects) with healthy controls. The effect of demographic variables and confounding factors like age of onset, duration of illness and medication status were analysed using the method of meta-regression.

RESULTS

While response inhibition, set shifting, executive function, verbal memory and sustained attention deficits were common features for both patient (medium to large effect sizes) and relative groups (small to medium effect sizes), processing speed, visual memory and verbal fluency deficits were only observed in patients. Medication effects contributed to psychomotor slowing in BD patients. Earlier age of onset was associated with verbal memory impairment and psychomotor slowing.

LIMITATION

Data related to some confounding variables was not reported in a substantial number of extracted studies.

CONCLUSIONS

Response inhibition deficit, a potential marker of ventral prefrontal dysfunction, seems to be the most prominent endophenotype of BD. The cognitive endophenotype of BD also appears to involve fronto-temporal and fronto-limbic related cognitive impairments. Processing speed impairment is related, at least partly, to medication effects indicating the influence of confounding factors rather than genetic susceptibility. Patterns of sustained attention and processing speed impairments differ from schizophrenia. Future work in this area should differentiate cognitive deficits associated with disease genotype from impairments related to other confounding factors.

Are neuropsychological deficits trait markers in OCD?

OBJECTIVE

Neuropsychological deficits are potential endophenotype markers. In obsessive-compulsive disorder (OCD), there is impairment in executive functions and nonverbal memory. However, studies have largely examined neuropsychological functioning in patients during the symptomatic phase. The state independent nature of neuropsychological deficits in OCD is not established. For neuropsychological deficits to be endophenotype markers, they have to be state-independent. We compared neuropsychological functions in recovered OCD patients with matched healthy controls.

METHOD

We assessed 30 recovered DSM-IV OCD patients without any concurrent comorbidity or lifetime history of schizophrenia, bipolar disorder, tics and alcohol/substance abuse and 30 healthy controls individually matched for age, sex and education. They were assessed on different neuropsychological dimensions: attention, executive function, memory and intelligence. For between-group comparisons, we employed univariate analyses, and to identify neuropsychological variables that differentiate cases and controls, we used backward conditional logistic regression for matched case-control design.

RESULTS

Patients in the recovered phase of the illness had significant deficits in tests of set-shifting ability, alternation, response inhibition and nonverbal memory but had intact performance in other tests. In the logistic regression, scores on the Wisconsin Card Sorting Test 'categories completed' and the Rey's Complex Fig. Test 'delayed recall' were significant after controlling for the possible confounding effects of age and education. There was no correlation between illness-related variables and neuropsychological deficits.

CONCLUSIONS

Deficits in certain executive functions and nonverbal memory are possibly state independent. Neuropsychological deficits are possibly candidate endophenotype markers for OCD and may help clarify genetic contributions. Future studies should evaluate unaffected siblings to establish deficits are endophenotype markers. Prospective studies with serial measurements of cognitive deficits are also needed to assess whether these deficits are cumulative with the progression of illness.

Verbal fluency dysfunction in euthymic bipolar patients: a controlled study

OBJECTIVE

To study the executive functioning in euthymic bipolar patients in comparison to healthy controls and to examine the relationship between neuropsychological deficits and clinical variables.

METHODS

Twenty-five euthymic bipolar patients and 31 controls underwent a battery of executive tasks including mental flexibility, inhibitory control and verbal fluency tests.

RESULTS

There were no significant differences between bipolar patients and controls in relation to mental flexibility and inhibitory control. However, patients performed worse than controls on verbal fluency tests. Poor performances on the Stroop Test and the Hayling and Brixton Tests--part A were associated to lifetime occurrence of psychotic symptoms, prior number of episodes, and previous hospitalizations.

CONCLUSIONS

In our study, only verbal fluency tests differentiated bipolar euthymic patients from healthy controls. Patients who showed deficits in information processing speed and inhibitory control had more episodes and hospitalizations and lifetime occurrence of psychotic symptoms.

Cognitive functions in euthymic state of bipolar disorder: an Indian study

INTRODUCTION

It has recently been observed that some cognitive deficits in bipolar disorders persist even after the subsidence of active symptoms. The authors aim to study the cognitive functioning of patients with bipolar disorder, currently in euthymia and compare them with normal healthy controls.

METHODS

Fifteen patients having bipolar-I disorder and currently in euthymia were compared with fifteen age- and education-matched controlled subjects. Cognitive assessments were done using three computer-based tests, i.e., Wisconsin's Card Sorting Test (WCST), Spatial Working Memory Test (SWMT), and Continuous Performance Test (CPT).

RESULTS

Euthymic bipolar patients showed significant deficits in executive functions. Subtle deficits were present in attention and working memory that were not statistically significant.

CONCLUSIONS

Executive deficits may be trait markers in bipolar disorder and may have clinical implications in patient rehabilitation.

The cognitive and neurophysiological basis of emotion dysregulation in bipolar disorder

BACKGROUND

Bipolar disorder is characterized by fluctuating affect and mood, and is associated with specific neurocognitive deficits consistent with neuropathology in cerebello-striatal-prefrontal neural networks. This network is critical for emotion regulation.

METHODS

Relevant literature was located via PsychINFO and Medline to provide a comprehensive review of cognitive and neural mechanisms of social information processing and affect generation in bipolar disorder (BD) in the context of recent research examining the neural mechanisms of emotion regulation via conscious cognitive strategies.

RESULTS

Emotion regulation relies on synergy within brainstem, limbic and cortical processes that promote the adaptive generation and regulation of affect, with prefrontal and cingulate regions inhibiting sub-cortical and cortical emotion processing systems in the cognitive control of emotional experience. Current evidence of structural and functional brain abnormalities in BD alongside aberrant social cognition, affect generation, and neuropsychological function are consistent with a model of emotion dysregulation to account for the symptoms of BD.

LIMITATIONS

A precise understanding of emotion dysregulation in BD is currently limited by a paucity of longitudinal research directly examining these issues.

CONCLUSION

Aberrant emotion perception alongside increased limbic activity during emotion perception and affect generation in BD, alongside impaired executive control associated with aberrant neurophysiological abnormalities in sub-regions of the prefrontal cortex, is consistent with impaired emotion regulation. We propose a cognitive and neurophysiological framework within which the variations of mood that are characteristic of BD can be understood as specific impairments of the cognitive control of emotion.