Factor analysis of the CORE measure of psychomotor disturbance in psychotic depression: Findings from the STOP-PD II study

The CORE instrument is commonly used to measure psychomotor disturbance. We examined the factor structure of the CORE in 266 adults with an acute episode psychotic depression, a disorder with a high rate of psychomotor disturbance. Exploratory factor analysis identified a two-factor solution: Factor 1 corresponded to the CORE's retardation and non-interactiveness items and Factor 2 corresponded to its agitation items. Internal consistency was excellent for Factor 1 but questionable for Factor 2. These findings suggest that the CORE's retardation and non-interactiveness items should be combined in one subscale when assessing patients with an acute episode of psychotic depression.