• Eye movement dysfunctions (EMDs), detectable during smooth pursuit, occur in a majority of schizophrenics and in 45% of their first-degree relatives. Previous data suggest that they represent a biologic marker for schizophrenia. To determine the mode of transmission of the schizophrenia-EMD complex, the eye movements of offspring of monozygotic and dizygotic twins were recorded. One group of twins was discordant for schizophrenia; the other group for manic depression or reactive psychosis. The data suggest that EMDs and at least some schizophrenias can be considered expressions of a single underlying trait that is transmitted by an autosomal dominant gene.
Holzman PS, Kringlen E, Matthysse S, Flanagan SD, Lipton RB, Cramer G, Levin S, Lange K, Levy DL. A Single Dominant Gene Can Account for Eye Tracking Dysfunctions and Schizophrenia in Offspring of Discordant Twins. Arch Gen Psychiatry. 1988;45(7):641-647. doi:10.1001/archpsyc.1988.01800310049006