Motor features in psychotic disorders. I. Factor structure and clinical correlates

The dimensional structure of motor disorders remains largely unknown. This study aimed to ascertain the factor structure of motor signs and their clinical correlates in psychotic disorders. A sample of consecutive admissions of psychotic patients (n=187) was utilized to examine the factor structure of motor disorders as assessed by the Modified Rogers Scale (MRS). The relationship between motor dimensions and external variables was analyzed. A comparative examination of alternative factor solutions revealed that a six-factor structure, explaining 59% of the total variance, best fitted the 36 MRS items. This solution comprised the components of motor poverty, agitation, stereotypy/mannerisms, proskinetic, negativistic and dyskinetic. All the motor dimensions significantly improved over the psychotic episode. Motor dimensions differentially correlated with the syndromes of psychoses, with the association between motor poverty and the negative syndrome being particularly strong. Residual motor pathology, but not the acute one, was related to various clinical variables. Residual symptoms of motor poverty and stereotypy/mannerisms were associated with poor premorbid adjustment, more illness severity and a diagnosis of schizophrenia. It is concluded that the factor structure of motor disorders and its clinical correlates are rather more complex than generally acknowledged.