By Mark Cowen
The unaffected first-degree relatives of patients with schizophrenia show subtle executive function impairments, and these deficits are associated with negative symptoms, investigators report.
"These deficits, which reflect subtle dysfunction in concept formation, flexibility, and mental shifting, may be seen as potential phenotypic markers of vulnerability for schizophrenia." says the team.
Silvia Scala and colleagues from the University of Verona in Italy studied 55 first-degree adult relatives of patients with schizophrenia and 55 gender-, age-, and education-matched controls without a family history of the disorder.
All of the participants completed a neurocognitive test battery as well as the Scale for the Assessment of Negative Symptoms (SANS), the Disability Assessment Scale (DAS), and the Global Assessment of Functioning Scale (GAF).
The researchers found that the relatives of schizophrenia patients had poorer overall performance on tests of executive function than controls.
Specifically, relatives had more preservative errors and fewer categories achieved (CA) on the Wisconsin Card Sorting Test (WCST) compared with controls, at 5.8 versus 4.2, and 4.2 versus 5.0, respectively, as well as lower scores on the Verbal Phonemic Fluency (VPF) test, at 35.4 versus 39.2.
The relatives of schizophrenia patients were also significantly more likely to test positive for at least mild negative symptoms on the SANS compared with controls, and also had poorer GAF and DAS scores.
The researchers also found significant negative correlations between all SANS subscale scores and WCST CA scores, as well as VPF test scores. No such correlations were observed in controls.
"Our findings suggest that adult non-psychotic first-degree relatives of patients with schizophrenia show signs of cognitive vulnerability to the disorder rather than early precursors to the illness," comments the team.
They add: "The finding of subtle executive impairment in the [relatives] group (which was independent of age and the kind of familial relationship) provides further support for the idea that these impairments may be seen as reliable intermediate phenotypes for schizophrenia."
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