Blowing hot and cold over depression and cognitive impairment

Abstract

In clinical practice, one may come across an elderly patient with severe and incapacitating depression. Typically, such a patient is morbidly preoccupied and hardly able to engage with the external world. If a person does not attend to external stimuli, then information is not registered efficiently. If information is not registered efficiently, then recall will be compromised, and impairment in learning and recall constitutes memory impairment in the true sense of the concept. Such a clinical scenario leads to an intuition that late-life depression is associated with cognitive impairment. Indeed, this clinical observation is also supported by cross-sectional clinical1,2 as well as population-based studies.3,4 Additionally, longitudinal studies have demonstrated depression to be a risk factor for incident dementia or mild cognitive impairment (MCI).5-7 These observational findings are supported by plausible neurobiological theories (table e-1 on the Neurology ® Web site at www.neurology.org).8 Counting the cross-sectional and longitudinal findings, one is tempted to conclude that the field of aging has taken 2 steps forward in establishing depression as a risk factor for incident dementia or MCI. However, the story does not end there. A number of other studies, including large prospective cohort studies, have reported no association between depression and cognitive impairment.9,10 Therefore, it appears that the field is blowing hot and cold in the same breath. Thus, we are well justified to seek more data to clarify this issue. The current issue of …