614 Neurocognitive Disorders
Functional Consequences of Major or Mild 
Neurocognitive Disorder Du e to Alzheimer’s Disease
The prominence of memory loss can cause significant difficulties relatively early in the
course. Social cognition (and thus social func tioning) and procedural memory (e.g., danc-
ing, playing musical instruments) may be relatively preserved for extended periods.
Differential Diagnosis
Other neurocognitive disorders. Major and mild NCDs due to other neurodegenera-
tive processes (e.g., Lewy body disease, fron totemporal lobar degene ration) share the in-
sidious onset and gradual decline caused by Alzheimer’s disease but have distinctive core
features of their own. In major or mild vascular NCD, th ere is typically history of stroke
temporally related to the onset of cognitive impairment, and infarcts or white matter hy-
perintensities are judged sufficient to accoun t for the clinical picture. However, particu-
larly when there is no clear hi story of stepwise decline, ma jor or mild vascular NCD can
share many clinical features with Alzheimer’s disease. 
Other concurrent, active neurological or systemic illness. Other neurological or sys-
temic illness should be considered if there is an appropriate temporal relationship and
severity to account for the clinical picture. At the mild NCD level, it may be difficult to dis-
tinguish an Alzheimer’s disease etiology from that of another medical condition (e.g., thy-
roid disorders, vitamin B12 deficiency). 
Major depressive disorder. Particularly at the mild NCD level, the differential diagnosis
also includes major depression. The presence of depression may be associated with re-
duced daily functioning and poor concentration that may resemble an NCD, but improve-
ment with treatment of depression may be  useful in making the distinction. 
Comorbidity