Motor and cognitive aspects of motor retardation in depression

Background: Motor retardation is a common feature of major depressive disor der having potential prognostic and etiopathological significance. Accordin g to DSM-IV, depressed patients who meet criteria for psychomotor retardati on, must exhibit motor slowing of sufficient severity to be observed by oth ers. However, overt presentations of motor slowing cannot distinguish slown ess due to cognitive factors from slowness due to neuromotor disturbances. Methods: We examined cognitive and neuromotor aspects of motor slowing in 3 6 depressed patients to test the hypothesis that a significant proportion o f patients exhibit motor programming disturbances in addition to psychomoto r impairment. A novel instrumental technique was used to assess motor progr amming in terms of the subject's ability to program movement velocity as a function of movement distance. A traditional psychomotor battery was combin ed with an instrumental measure of reaction time to assess the cognitive as pects of motor retardation. Results: The depressed patients exhibited signi ficant impairment on the velocity scaling measure and longer reaction times compared with nondepressed controls. Approximately 40% of the patients dem onstrated abnormal psychomotor function as measured by the traditional batt ery; whereas over 60% exhibited some form of motor slowing as measured by t he instruments. Approximately 40% of the patients exhibited parkinsonian-li ke motor programming deficits. A five-factor model consisting of motor meas ures predicted diagnosis among bipolar and unipolar depressed patients with 100% accuracy. Limitations: The ability of motor measures to discriminate bipolar from unipolar patients must be viewed with caution considering the relatively small sample size of bipolar patients. Conclusions: These findin gs suggest that a subgroup of depressed patients exhibit motor retardation that is behaviorally similar to parkinsonian bradykinesia and may stem from a similar disruption within the basal ganglia. (C) 2000 Elsevier Science B .V. All rights reserved.