Differential patterns of psychomotor functioning in unmedicated melancholic and nonmelancholic depressed patients

Abstract

Few studies examining psychomotor retardation (PR) in patients with major depressive disorder (MDD) included medication-free patients. The purpose of this study was (1) to examine whether unmedicated patients with MDD would exhibit PR, (2) to determine whether this retardation, if present, was more cognitive or motor in nature, and (3) to investigate whether any differences in PR could be established between melancholic and nonmelancholic depressed patients. Thirty-eight unmedicated inpatients with severe MDD (20 melancholic and 18 nonmelancholic patients) and 38 matched controls were compared on figure-copying tasks in which the cognitive task difficulty was manipulated. In addition, a simple motor task and the symbol digit substitution task (SDST) were administered. As a group, the patients were significantly slower performing all tasks and both initiation times (IT) and movement times (MT) were prolonged. However, when a distinction was made between the two subtypes, only the melancholic patients showed prolonged MTs compared to the controls. Furthermore, the melancholic patients differed significantly from the controls in IT in all tasks. The nonmelancholic patients had significantly longer ITs than the controls in two copying tasks. It can be concluded that there was clear cognitive and motor slowing in this group of unmedicated inpatients with MDD. The melancholic patients were more severely affected than the nonmelancholic patients and showed a slowing of cognitive as well as motor processes. Differences in psychomotor functioning between melancholic and nonmelancholic depressed patients could imply different underlying neurobiological disturbances in these subtypes of major depression.