Pseudo-dementia: A neuropsychological review.

Sir,

We read the recent publication on Pseudo-dementia: A neuropsychological review and found it informative and very interesting.[1] Presence of depression in elderly could be part of dementia itself, and hence, it merits adequate clinical attention. It has been demonstrated that depression can adversely affect neuropsychological functions including attention and concentration, processing speed, and memory.[234] However, it could be debatable whether these cognitive deficits are due to state/trait marker(s) of depression or prodromal phase of dementia.[2] We would like to add our observation in brief regarding the neuropsychology of depressive pseudo-dementia.

In our opinion, several methodological issues need to be taken into consideration because they could confound the findings. Firstly, depression is a heterogeneous condition in terms of severity, duration, and comorbidities. The number of depressive episodes, severity, and duration of each episode are known to affect cognitive functions differently.[2] In addition, other factors such as comorbid conditions, (e.g. presence of psychosis and substance use,) could also complicate the neuropsychological profile. Further, the effects of medication on cognitive functions can create additional complications as several medications are known to affect cognitive functions adversely.[2] Secondly, neuropsychological assessment (procedure) related issues, for example, the use of different neuropsychological tests in different studies, can also complicate the picture. Another important factor is testing time; whether the assessment was done during euthymic state or depressive episode can exert powerful impact on cognition.[4] Therefore, caution needs to be exercised while collating findings from different studies and arriving at conclusions.

Neuropsychological assessment provides an opportunity to examine the functioning brain through observations. In our opinion, behavioral observation during assessment is extremely crucial and vital for test interpretation. Many depressed patients may lack sufficient motivation to complete the task, take more time to complete the task, and report attention or concentration difficulty. Moreover, depressed patients often report memory problem repeatedly and also recollect when and where memory lapses occurred.[3] Contrary to this, demented patients are often less aware of the extent of their cognitive deficits. The patients with dementia are less likely to experience the vegetative features of depression while the depressed patients may often somatize their distress.[3]

Attention (focused) is the fundamental requisite for neuropsychological assessment and inhibition of task-irrelevant information is crucial for adequate cognitive performance. It is well-known that negative automatic thought (NAT) and ruminations are very much part of depression, intrude into the consciousness due to depressive state, and may affect cognition.[4] Patients with depression often exhibit reduced inhibition of these negative materials and find it difficult to disengage attention from irrelevant material (NAT) in order to focus on the ongoing cognitive task.[4] We are tempted to speculate that reduction in cognitive control or inhibition could produce a generalized effect on different cognitive domains rather than cause deficit in an isolated domain.

With regard to neuropsychological profile, it has been consistently reported that depressive pseudo-dementia patients perform relatively better than patients with true dementia and the severity of impairment is noted to be much greater in Alzheimer Dementia.[3] Neuropsychology of dementia has been explored extensively in the last few decades and attention has been shifted to exploring cognitive profile of the preclinical phase (mild cognitive impairment), which can enhance our understanding and enable us to identify early Alzheimer Dementia as well as help us to distinguish it from depressive pseudo-dementia.[35]

Taken together, depression is a heterogeneous condition that could affect several domains of cognition including memory functions, and its relationship with dementia needs to be explored using rigorous research designs and well-defined samples. Clinically, neuropsychological examination findings must be integrated with detailed exploration (regarding onset and presence of cognitive deficits and depression) and careful behavioral observations to enable differentiation of depressive pseudo-dementia from true dementia.