Voluntary motor performance in psychotic disorders: a replication study

Voluntary motor performance was used to investigate the hypothesis of a continuum of psychosis from depression through schizophrenia. 43 schizophrenic, 36 schizoaffective, 50 major depressive, 20 manic, and 25 nonpsychotic patient controls were tested for tapping speed, finger dexterity, hand grip strength, and neuropsychological motor performance. Sex was included as an independent variable, and the effects of psychotropic drugs were evaluated. A continuum of motor dysfunction from depression through schizophrenia was not obtained. A measure of current psychotic symptoms was not associated with motor or neuropsychological performance. Motor performance was significantly worse in schizophrenic, schizoaffective, and psychotic affective disorders, when compared to nonpsychotic affective disorders. In this final analysis, psychoticism was defined by history. The results are discussed in terms of the hypothesis that psychoticism is a trait that is independent of diagnosis.