642 Neurocognitive Disorders
Development and Course
Typically the course of the NCD progresses in a manner that is commensurate with progres-
sion of the underlying medical disorder. In ci rcumstances where the medical disorder is treat-
able (e.g., hypothyroidism), th e neurocognitive deficit may im prove or at least not progress.
When the medical condition has a deteriorative course (e.g., secondary progressive multiple
sclerosis), the neurocognitive deficits will progre ss along with the tempor al course of illness.
Diagnostic Markers
Associated physical examinatio n and laboratory findings and other clinical features de-
pend on the nature and severity of the medical condition. 
Differential Diagnosis
Other major or mild neurocognitive disorder. The presence of an attributable medical
condition does not entirely exclude the possibility of another major or mild NCD. If cog-
nitive deficits persist following successful treatment of an associated medical condition,
then another etiology may be responsible for the cognitive decline.
Major or Mild Neurocognitive Disorder
 Due to Multiple Etiologies
Diagnostic Criteria  
A. The criteria are met for major or mild neurocognitive disorder.
B. There is evidence from the history, physical examination, or laboratory findings that the
neurocognitive disorder is the pathophysiological consequence of more than one etio-
logical process, excluding substances (e.g., neurocognitive disorder due to Alzhei-
mer’s disease with subsequent development of vascular neurocognitive disorder).
Note:  Please refer to the diagnostic criteria for the various neurocognitive disorders due
to specific medical conditions for guidance  on establishing the pa rticular etiologies. 
C. The cognitive deficits are not better ex plained by another mental disorder and do not
occur exclusively during the course of a delirium.