Genetic influence on laterality in schizophrenia? A twin study of neurological soft signs

Objective: This study explored the genetic basis of neurological soft signs in schizophrenia and addressed disturbed hemispheric lateralization. Metho d: The authors investigated neurological soft signs in 30 monozygotic twin pairs, 13 pairs discordant for schizophrenia or schizoaffective disorder an d 17 healthy comparison twin pairs. Results: The twins with schizophrenia s howed higher total scores for neurological soft signs than did the comparis on subjects. The total scores for neurological soft signs of the nonaffecte d discordant twins were significantly higher than those of the comparison t wins. There was a significant difference between the nonaffected and affect ed discordant twins in total scores for neurological soft signs, in contras t to the comparison subjects, the nonaffected and affected twins of the dis cordant pairs showed a trend toward higher scores for neurological soft sig ns on the left body half. Conclusions: These results suggest that the occur rence of neurological soft signs and, more specifically, their lateralizati on to the left body half are genetically transmitted.