Executive functioning and verbal memory in young patients with unipolar depression and schizophrenia

Although neuropsychological studies have consistently reported executive deficits in schizophrenia, studies of executive functions in depression have produced equivocal results. The aim of this study was to examine the profile and the specificity of the executive impairment and its association with memory performance in young patients with unipolar depression. We compared patients with depression to normal control subjects and schizophrenics. Twenty young inpatients with unipolar depression, 14 schizophrenics and 20 age-, education- and IQ-matched control subjects were assessed with a neuropsychological battery including: (1) verbal memory task; (2) frontal tasks (WCST, Cognitive Estimate, Verbal fluency, verbal and visuo-spatial span) and a new complex sorting test (Delis test). Depressed patients and schizophrenics exhibited executive deficits. Unlike schizophrenics, depressed patients did not show memory impairment. Deficits in several 'higher-level' functions combined to produce executive impairments in patients with depression including complex integration for concept formation, spontaneous cognitive flexibility and initiation ability. Impaired functions in schizophrenia and in depressed patients were similar but were differently related to clinical variables. The pattern of memory failure in our schizophrenics is believed to reflect retrieval and encoding deficits. Our findings highlight the heterogeneity of skills grouped under the term 'executive functions' that are vulnerable in depression or schizophrenia.