Comorbidity of mild cognitive disorder and depression - a neuropsychological analysis

Abstract

Mild cognitive impairment is found in many cases of depression, and it is mostly assumed to improve during the time course of depression remission. Recent data question the reversibility of low cognitive test performance in depression. The aim of this study is to determine the degree of reversibility and the proportion of patients who will not demonstrate reversibility of cognitive dysfunction. Consecutive inpatients suffering from depression (N=102) were investigated and N=82 matched control subjects. N=57 of the patients were diagnosed as major depression according to DSM-IV. A total of N=67 could be retested after remission of depression (N=32 of the patients with major depression) and a matched control group (N=62). Neuropsychological tests were applied in a test session which avoids the effects of fatigue in the patients by the short duration of strenuous tests. For most neuropsychological tests an impaired performance in the depressed patients was found. About one third of the depression subjects performed at an impaired level in tests of averbal memory and verbal fluency (below 5th percentile). In the follow-up investigation, a slight improvement in performance could be assessed for both the depression and the control group, which was, however, attributed to a general test training effect. No normalization of cognitive test performance was found in spite of complete recovery of the affective symptoms. No correlation between the duration of the disease before the index episode or number of episodes and cognitive deficits could be found. The data of the neuropsychological deficits of depressed patients, which are stable in the time course of the affective disorder, may indicate that these patients may suffer from comorbidity of both depression and mild cognitive disorder. The findings are discussed as 1) indicating only a minor impact of the depressed mood on the cognitive performance and 2) they are consistent with a role of brain lesions which have been reported in several studies in a subgroup of depression.

Course of Illness, Hippocampal Function, and Hippocampal Volume in Major Depression

“…Recollection memory performance was not predicted by Ham-D or BDI-II scores in this study, and using the process dissociation task in a separate group of individuals with current or remitted depression we previously found recollection memory impairment after remission of depressive symptoms (16). These data are consistent with previous work of Sheline et al (3), which demonstrated list-learning deficits in patients in remission, and other recent reports of memory impairment persisting into the euthymic period (47,48). Whether these deficits ultimately resolve remains to be established.…”

Reliability and Validity of the Massachusetts General Hospital Cognitive and Physical Functioning Questionnaire

“…Initially such impairments were considered to be related to acute or subsyndromal mood episodes. However, there is now substantial evidence that subjects with unipolar and bipolar mood disorders exhibit cognitive impairments even when they are euthymic [7,8,9,10,11]. While impairment of executive function was reported by some [9] but not all studies [12, 13], deficits of attention and verbal memory have been reported by a majority of researchers [12,14,15,16,17,18].…”

Late-Onset Depression with Mild Cognitive Deficits: Electrophysiological Evidences for a Preclinical Dementia Syndrome

“…Manifold clinical associations and comorbidities make their differential diagnosis and the subsequent therapeutic decisions delicate. Clinical uncertainties are especially pronounced in cases of late-onset depression with cognitive deficits, which are present in up to 60% of elderly depressed patients [1] and now known as a risk factor for dementia [2,3]. Presently, the question whether mild cognitive deficits [mild cognitive impairment (MCI)] are reversible epiphenomena of depression, precursors of dementia or represent an independent disorder can only be determined by monitoring the course of the disease.…”