Cognitive deficits in severe mood disorder: similar or different from schizophrenia?

The border of affective psychosis with schizophrenia can be understood with reference to a range of comparative similarities and differences in Genetics, 'Environment', Phenomenology, Neuropsychology, Imaging and Neuropharmacology. The conditions share some of the genetic contribution and have similar complex multidimensional phenotypes, and overlapping symptoms of psychosis. Neuropsychological paradigms offer fresh insight into the links between symptomatology, elemental cognitive functions, and the underlying neural substrates of abnormal mental states. In the manic phase of bipolar disorder, verbal learning and sustained attention (the RVIP) correctly classify 87% of manic subjects and 91% of subjects overall [1]. In the euthymic state only attentional performance was impaired after controlling for low levels of affective symptoms [2, 3]. The effect was almost as large as in the acute group and was related to number of illness episodes. The CVLT was most impaired in patients with persisting affective, almost entirely depressive symptoms. In severe depression abnormalities of cognitive function are tightly coupled to prevailing mood, even when studied in a diurnal design. The salience of memory impairments is pervasive. Motor slowing and impairment of executive function is most definitively related to depressed states in which clinical retardation is prominent [4]. Chronic depression is associated with memory impairment and MRI abnormality in the hippocampus [5]. The central tenet of recovery in bipolar patients has already been challenged by the high incidence of occupational and psychological difficulties during remission. Impaired sustained attention may represent a trait marker for bipolar disorder, related to vulnerability to the disorder at a structural and/or neurochemical level. In unipolar depression poor outcome is usually related to residual depressive symptoms, and cognitive impairment. Impaired memory function is a state marker sensitive to mood elevation or depression.