Psychomotor disturbances in psychiatric patients as a possible basis for new attempts at differential diagnosis and therapy. II. Cross validation study on schizophrenic patients: persistence of a "psychotic motor syndrome" as possible evidence of an independent biological marker syndrome for schizophrenia.

This study investigates the existence and course of psychomotor symptoms in schizophrenic patients (n = 57, both treated and untreated with antipsychotic drugs) as compared to 25 healthy controls. Previous psychometric studies had suggested the existence of a "psychotic motor syndrome" (PMS) both in (untreated) schizophrenic and endogenous depressed patients, consisting of disturbances of lip and tongue movements, fine and gross movements of the dominant right hand and impaired complex motor coordination of the extremities. We confirmed the existence of the PMS in this study. There was no correlation of the PMS with the psychopathological status of the patients, or with extrapyramidal side-effects of the drugs used, perhaps indicating an independent "basic syndrome" ("Basisstörung"). Factorial analyses revealed similar structures both in schizophrenic and healthy persons; the differences in motor performance may be due to an impairment of the first factor "general motor ability" in schizophrenic patients. The PMS did not disappear parallel to the psychopathological improvement of the patients, nor in the symptom-free remission interval. The role of the PMS as possible independent biological marker syndrome for schizophrenia can consequently be further supported, with its implications towards the differential diagnostic and therapeutical values of this syndrome.