Quantitative assessment of motor abnormalities in untreated patients with major depressive disorder

The primary purpose of this study was to examine motor physiology disturbances in a group of patients with untreated major depressive disorder using sensitive instrumental procedures. The secondary aim of the study was to examine the relationship of the affective symptom state to these motor assessments. The authors studied 40 individuals meeting DSM-IV criteria for unipolar major depressive disorder and 40 healthy comparison subjects. Electromechanical measures of force steadiness (FS), simple reaction time (RT), movement time (MT) and scaling of movement velocity to distance (velocity scaling, VS) were performed. The authors found that performance on the force steadiness, movement time, and velocity scaling measures was significantly poorer in the subjects with depression. There was no difference between the groups on the measure of reaction time. The force steadiness, reaction time, movement time, and velocity scaling scores were not associated with affective state. This study demonstrates that motor abnormalities suggestive of basal ganglia dysfunction occur in many patients with major depressive disorder, and that these abnormalities may exist in the absence of current psychotropic medication treatment. The finding of impaired movement time and velocity scaling in the presence of normal reaction time suggests a neuromotor or parkinsonian pathophysiology for slowness in depression.