Cognitive neuropsychiatry is a sub-discipline of psychology and psychiatry that aims to understand mental illness and psychopathology in terms of models of normal psychological function. It is also a way of uncovering normal psychological processes by studying the effects of their change or impairment. It is derived from the fields of psychiatry, cognitive neuroscience, and cognitive neuropsychology.
It is a relatively new discipline and only started in earnest in the 1990s but has been influential, not least because of its early successes in explaining some previously mysterious psychiatric disorders, most notably the Capgras delusion and other delusional misidentification syndromes.

Further reading

Halligan, P.W. Marshall, J.C. (1996) Method in Madness: Case Studies in Cognitive Neuropsychiatry. Psychology Press. ISBN 0-86377-442-3
Halligan, P.W., and David, A.S. (2001). Cognitive Neuropsychiatry: towards a scientific psychopathology. Nature Neuroscience Review, 2, 209-215.