Specific cognitive deficits in a group at genetic high risk of schizophrenia

Neuropsychological deficits in schizophrenia patients and their relatives have been thought to represent possible genetic vulnerability markers or endophenotypes of the disorder. The present study describes results from the Edinburgh High Risk Study of computerized testing using the Cambridge Neuropsychological Test Automated Battery (CANTAB) on a group at genetic high risk (HR) of schizophrenia and a control group.

A total of 97 HR and 25 control participants were assessed on three tests from the CANTAB - spatial span, spatial working memory, and Stockings of Cambridge. Analyses of covariance were used to compare the HR and control groups on the main outcome measures whilst controlling for intelligence quotient (IQ). Subsequent analysis examined the effects of the presence of symptoms on group differences.

HR participants had significantly reduced spatial memory capacity [F(1, 118)=4.06, p=0.046] and significantly reduced planning processing speed [F(1, 116)=4.16, p=0.044] compared with controls even after controlling for general intelligence (IQ). Although HR individuals made more errors and showed poorer problem-solving and strategy performance compared with controls, these differences were not significant after controlling for IQ. Subsequent analysis indicated that the presence or absence of psychotic symptoms in the HR group did not influence these specific cognitive deficits.

Spatial memory capacity and planning processing speed may represent cognitive endophenotypes characterising the genetic predisposition to schizophrenia in this HR group.