Can cognitive deficits facilitate differential diagnosis between at-risk mental state for psychosis and depressive disorders?

AIM: Many studies have provided evidence of cognitive deficits in individuals in an 'At Risk Mental State' (ARMS) for psychosis, which makes neuropsychology potentially useful in the early detection of psychosis. As depression is an important differential diagnosis in prodromal states of psychosis, the specificity of neurocognitive deficits in ARMS individuals as compared with non-psychotic depressive disorders is investigated. METHODS: Neurocognitive performance of four groups was analysed: 22 ARMS individuals with later transition to psychosis (ARMS-T), 25 ARMS individuals without later transition to psychosis (ARMS-NT), 34 controls with depressive disorders and 76 healthy controls. The subjects were assessed with a neurocognitive test battery covering the domains' intelligence, executive function and attention/ working memory. MANOVAs, ANOVAs and Tukey's tests were applied after adjustment for confounding factors. RESULTS: ARMS-T showed significant cognitive deficits in working memory and in certain executive function tasks compared with healthy controls as well as with controls with depression. Controls with depression were only impaired in time per move in the tower of Hanoi test when compared with healthy controls. CONCLUSIONS: The psychosis prodrome seems to be associated with cognitive deficits in the domains of working memory and executive function. In contrast, depressive patients showed no cognitive deficits, but slowing in one executive function task. Neurocognitive testing might therefore contribute to the differential diagnosis between prodromal psychosis and depressive disorders.