P300 and neuropsychological measurements in patients with schizophrenia and their healthy biological siblings

BACKGROUND: Patients with schizophrenia and their first-degree relatives' exhibit abnormalities in neuropsychological and electrophysiological measures especially P300. The aim was to study the P300 and neuropsychological measures together in patients with schizophrenia, their unaffected siblings, and normal controls. MATERIALS AND METHODS: Thirty patients diagnosed as schizophrenia, their unaffected biological siblings, and normal controls were included in the study. Inpatient group, the severity of symptoms was assessed by Positive and Negative Syndrome Scale. All subjects were administered P300 event-related potential, which was measured using oddball paradigm and specific neuropsychological tests from NIMHANS neuropsychiatry battery. RESULTS: Both patients with schizophrenia and their unaffected biological siblings showed lower P300 amplitude and longer P300 latency when compared with the normal controls. The three groups showed statistically significant differences in digit symbol substitution test, digit vigilance test, Trail making test B and Stroop test (P < 0.001). CONCLUSION: Patients with schizophrenia and their unaffected biological siblings show deficits in both cognitive function tests and P300 event-related potential. Our results suggest a continuum in the electrophysiological and neuropsychological measures among the three groups.