A longitudinal study relating P3 amplitude to schizophrenia spectrum disorders and to global personality functioning

Auditory and visual event-related potentials (ERPs) were recorded from first-degree relatives (adolescent offspring) of index cases with schizophrenic disorder, affective disorder, or no psychiatric disorder (normal controls) at a mean age of 15 years. Nearly a decade later, these subjects (at a mean age of 25 years) were evaluated for Research Diagnostic Criteria Schizophrenic Disorder, Schizoaffective Disorder, Unspecified Functional Psychosis, and for DSM-III-R Axis II schizophrenia-related traits and disorders including schizotypal, schizoid, and paranoid features. It was hypothesized, based on Duncan et al (1987a, Duncan 1988), that reduction of P3 amplitude in the auditory (but not the visual) modality would predict subsequent schizophrenic-related outcomes in subjects from the schizophrenic disorder parental group. This specific expectation was not statistically supported. An unanticipated and statistically robust result linking P3 decrements (in both auditory and visual modalities) with poorer Global Personality Functioning was observed for offspring from both psychiatric parental groups and the offspring of the normal control group. These data are consistent with the results of a large number of clinical studies of the P3 component that have demonstrated reductions in P3 amplitude in individuals expressing a wide range of behavioral dysfunctions. Their importance lies in the fact that these P3 amplitude decrements were detected long before the overt behavioral symptoms were identified, and were nonspecific with respect to parental psychiatric diagnostic group.