Cognition includes memory, language, orientation, judgement, planning, conducting interpersonal relationships, performing actions and problem-solving. Neurocognitive disorders (dementias) reflect acquired deficits in cognitive function, and hence they represent a decline from a previously attained level of functioning. These conditions are often associated with behavioural symptoms. These symptoms include anxiety, depression, sleeping problems, aggression and psychosis. The complex interface between neurology, medicine and psychiatry is demonstrated here since medical and neurological conditions can lead to neurocognitive disorders that are in turn associated with behavioural symptoms. The elderly are most at risk for neurocognitive disorders, especially the dementias of late life. A younger person may develop a neurocognitive disorder following a serious head injury, as a result of an infection that affects the brain, or as a result of substance misuse.
Other causes of neurocognitive disorders include Alzheimer’s disease, Parkinson’s disease, Huntington’s disease and vascular disease of the brain.