Neurological "hard" signs and family history of psychosis in schizophrenia.

Previous research found schizophrenics to have significantly more neurological signs than normal controls, even when signs were screened to exclude possible artifacts, and limited to "hard" signs of localizing significance. Schizophrenics with a family history of psychosis also tended to have more neurological signs than those without such a history. The present study examined whether these findings could be confirmed in new samples of schizophrenics and controls, using interview-based DSM-III and DSM-III-R diagnoses. Schizophrenics had significantly more hard signs than controls, and schizophrenics with a family history for psychosis again had more signs than those without this history. When present study data were analyzed alone, as well as when pooled with data from previous research using similar methods, hard signs were significantly greater in both (a) schizophrenics versus controls and (b) schizophrenics with versus without a family history of psychosis, supporting the hypothesis that neurological signs reflect a significant etiologic factor in schizophrenia.