Cognitive impairment in bipolar II disorder
Torrent C, Martinez-Aran A, Daban C, Sanchez-Moreno J, Comes M, Goikolea JM, et al.;
Commented by , 27 Sep 2006
Background/Aims
In DSM-IV, Bipolar I is classified as one or more episodes of mania; Bipolar II as mania interspersed with depressive episode(s). There is mounting evidence that the cognitive impairment evident in the acute phase of Bipolar Disorder persists when the acute phase of the illness is past, ie., when the patient is euthymic. This study sought to compare cognitive impairment in Bipolar I and II Disorder compared to healthy controls.
Method
Subjects were already enrolled in the wider Bipolar Disorders Programme in Barcelona. All were currently euthymic, medically fit, and with no co-morbid substance misuse disorder. Controls were recruited through an advertisement and from a pool of healthy volunteers.
Demographic data and history of the affective illness was collected by a Psychiatrist who additionally assessed psychosocial functioning with the Global Assessment of Functioning Scale.
Neuropsychological testing was performed by a Neuropsychologist blind to the other assessments. Participants completed a comprehensive battery of tests estimating IQ, frontal executive function, attention/concentration, and verbal learning and memory.
Statistics – the three groups were compared on clinical and sociodemographic variables using analysis of variance (ANOVA) and chi-squared tests. MANOVA was used to compare differences in neuropsychological tests between groups.
Results
The three groups did not differ in gender, educational level or functional outcome. The Bipolar I group were slightly younger (mean age 38.4 years, standard deviation 8.7), and had a younger onset of illness.
Patients with Bipolar II disorder had verbal memory and perseverative deficits compared to controls. Bipolar I patients had quantitatively more dysfunction than Bipolar II. After controlling for age, both groups had worse performance than controls on working memory and attention.
Dr Seymour's comments
There can be no doubt that cognitive deficits in manic depression persist into the euthymic state. This study suggests that Bipolar II patients have similar cognitive deficits to Bipolar I, though to a lesser degree; the deficits are principally in verbal memory and executive function.
What is the significance of these findings for clinicians? Firstly, there is an imperative for early diagnosis and effective treatment of index episodes – this may limit cognitive damage, though no longitudinal study has examined this. Secondly, cognitive deficits need to be taken into account in rehabilitation of patients with bipolar disorders. Thirdly, this study has significance for Old Age Psychiatrists – even though this study examined patients in their 30s and 40s – who may be asked to examine bipolar patients for evidence of dementia.
This study further emphasises that severe affective illness damages the brain. As with schizophrenia, the most severe forms of Bipolar Disorder could now be regarded as an "organic", not a "functional" disorder.