Case for and against specificity of depression in Alzheimer's disease

The aims of this study were to assess the epidemiological, phenomenological, and pathophysiological evidence that suggests the specificity of depression associated with Alzheimer's disease (AD).

We reviewed the English-language literature.

Depression occurs significantly more often in patients with AD than in the general elderly population. While development of depression in response to the disability and emotional stress of AD may be a contributory factor in some patients, several studies showed that depression was not, or was only seldom, related to self-awareness of AD and these studies could not explain the high prevalence figures. To overcome the overlapping phenomenology of the two diseases, specific diagnostic criteria have been developed for depression in this context. Mixed findings have come from neuropathological and neuroimaging studies, with some evidence linking the underlying neural substrate of AD and depression, suggesting an overlapping cause of primary depression and depression comorbid with AD. Few randomized controlled trials for depression associated with AD have been conducted, with rather poor results for the use of antidepressants.

Currently, depression associated with AD is not considered a separate disorder by regulatory authorities and is unlikely to be considered as such in the near future. Several obstacles remain to support such a specific position, including the heterogenous nature of depression in general and within AD itself, the lack of a distinct set of symptoms, and limited treatment.