Impairment of executive function in elderly patients with major unipolar depression: influence of psychomotor retardation

The results from several studies assessing the executive function in depressed patients compared to control subjects varied from significant impairment to normal performance. To assess the executive impairment in elderly patients with major unipolar depression and to evaluate the influence of psychomotor retardation and severity of depression in the executive deficits, the performance of 15 elderly patients with unipolar depression was compared to that of 15 elderly control subjects on executive tasks. The severity of depression was evaluated by the Montgomery and Asberg depressive scale and that of psychomotor retardation by the Widlocher's scale. In depressed patients, deficits were found on tasks assessing cognitive flexibility (Modified card sorting test (MCST) and Trail making test B), planification and elaboration of strategies (cognitive estimates), motor initiation (graphic sequences), categorisation and hypothesis making (MCST) and interference resistance (Stroop test). However, depressed patients performed normally on the Hayling test assessing the inhibition processes. Intensity of psychomotor retardation was not correlated to the performance of executive tasks. Conversely, severity of depression was related to the scores of MCST (number of errors and perseverations), Stroop and Hayling tests (timetaken to complete the end of the sentence). Unipolar depressed patients showed deficits in most tasks assessing executive function. However, inhibition processes appeared to be intact in depressed patients although their implementation was difficult. The severity of depression but not that of psychomotor retardation was associated with executive deficits.