Genetic and state variables of neurocognitive dysfunction in schizophrenia: A twin study

To characterize the familiality of cognitive dysfunction in schizophrenia, me studied performance on three tasks (visuospatial attention; visuolinguis tic conflict, arrow-word; and Wisconsin Card Sorting Test [WCST]) by monozy gotic (MZ) and dizygotic (DZ) twin pairs discordant for schizophrenia. The subject sample consisted of six MZ twin pairs, nine DZ twin pairs, and one MZ and one DZ nonschizophrenia cotwin of a patient with schizophrenia. Ther e were two sources of cognitive dysfunction: a nonheritable, state componen t and a heritable, trait component, Deficits surfaced during the WCST in no nschizophrenia MZ cotwins; this impairment resolved following training in n onschizophrenia MZ cotwins, but not in the probands with schizophrenia, who performed abnormally in all tasks, The results suggest that nonheritable p rotective factors modulate the specific, plastic, and sometimes subtle neur ocognitive deficits related to the schizophrenia genotype.