591Neurocognitive
 Disorders
The neurocognitive disorders  (NCDs) (referred to in  DSM-IV as “Dementia,
Delirium, Amnestic, and Other Cognitive Di sorders”) begin with delirium, followed by
the syndromes of major NCD, mild NCD, an d their etiological su btypes. The major or
mild NCD subtypes are NCD due to Alzheimer’s disease; vascular NCD; NCD with Lewy
bodies; NCD due to Parkinso n’s disease; frontotemporal NCD; NCD due to traumatic
brain injury; NCD due to HIV infection; su bstance/medication-induced NCD; NCD due
to Huntington’s disease; NC D due to prion disease; NCD du e to another medical condi-
tion; NCD due to multiple etiologies; and unspecified NCD. The NCD category encom-
passes the group of disorders in which the primar y clinical deficit is in cognitive function,
and that are acquired rather than developmental. Although cognitive deficits are present
in many if not all mental disorders (e.g., schizophrenia, bipolar diso rders), only disorders
whose core features are cognitive are includ ed in the NCD category. The NCDs are those
in which impaired cognition has not been present since birth or very early life, and thus
represents a decline from a previou sly attained level of functioning.
The NCDs are unique among DSM-5 categories in that these are syndromes for which
the underlying pathology, and frequently the etiology as well, can potentially be deter-
mined. The various underlying disease entities  have all been the subject of extensive re-
search, clinical experience, and expert consen sus on diagnostic crit eria. The DSM-5 criteria