Cognition in psychiatry usually refers to the diagnosis of a disturbance in the capapcity to engage in a cogntive process.
Remarkably, the most dangerous disturbance of cognition, delirium, is not generally recognized by neurologists as an ailment that falls within their proper clinical sphere of attention.
At its simplest, cognition is the capacity to retain and reproduce bits of information. For this reason, deficits are easy to find, and accompany a range of illnesses.
Delirium deserves special discussion as a medical emergency. Delirium is most often described as a waxing and waning of sensorium. It is always a product of acute disturbances in the organism.
Because of its origins, it is not seen as a proper topic of diagnosis by many psychiatrists.
For instance, it is generally recognized that demnetia raises the risk of delirium. Yet there is no formal DM IV diagnosis of delirium with underlying dementia, and subsequently, the signposts to the treatment of dementia are easily missed.