Depressive symptom quality and neuropsychological performance in dementia

It is unknown to what extent depression and cognitive dysfunction are related in subjects with dementia. A limitation of earlier studies is that only general measures of depression have been studied.

In a sample of 60 subjects with dementia according to DSM-III-R criteria depressive symptoms were divided into factors of mood and motivation disturbance according to a principal components analysis. Correlations were computed between the factor scores and the performance on a number of specific neuropsychological tests. As the symptom content of motivation disturbance suggests subcorticofrontal dysfunction it was hypothesized that this factor is related to impaired executive functions.

77% of the depressive symptoms contributed to the dimension of motivation disturbance and most of these symptoms occurred outside the context of a major depressive episode. Our hypothesis was supported by a significant negative correlation between motivation symptoms and semantic verbal fluency. This relationship seems to have specificity, as both the dimensions of mood symptoms and of general depressive symptoms did not correlate significantly with specific neuropsychological test scores.

The division of depressive symptoms in factors of mood and motivation disturbance contributes to insight into the relationship between depression and cognitive dysfunction in dementia. An advantage of the motivation disturbance factor compared to the regular apathy scales is that it consists of depressive symptoms. Therefore, it becomes evident that apathy or impaired motivation may occur in patients with dementia both in and outside the context of a depressive syndrome.