Cognitive functioning in siblings discordant for schizophrenia.
OBJECTIVE: The objective of this study was to investigate neuropsychological impairment as a genetically mediated risk indicator for schizophrenia while accounting for prevalence of schizotypy signs/symptoms in siblings. METHOD: Cognitive functioning in 25 individuals with schizophrenia, 25 unaffected siblings and 25 unrelated healthy controls, was assessed using neuropsychological tests of sustained attention, memory and learning, executive function, visual-spatial ability and psychomotor performance. RESULTS: Unaffected siblings demonstrated better performance than patients on some measures of memory and learning and executive function. Patients and siblings demonstrated impaired Full Scale IQ and verbal fluency, otherwise siblings performed similarly to healthy controls. Controlling for differences in IQ, the shared deficit in verbal fluency disappeared. CONCLUSION: Patients with schizophrenia and unaffected siblings (without schizotypy personality disorder) shared a neuropsychological deficit in verbal fluency. This deficit appeared to be mediated by IQ. Deficits, which differentiated patients from controls, may not be inherited and perhaps are related to the manifestation or treatment of schizophrenia.