Background: The P300 component of the auditory event-related potential (ERP
) is both reduced in amplitude and delayed in schizophrenia. P300 is prolon
ged and, less consistently, reduced with normal aging. Additional latency d
elays are observed in neurodegenerative disorders. We asked whether P300 is
reduced and delayed with longer illness duration in schizophrenia, consist
ent with a neurodegenerative process.
Methods: P300 amplitude and latency were recorded to infrequent auditory ta
rget stimuli from 35 men with schizophrenia (DSM-III-R) and 26 control men.
Effects of current age, age of onset, and duration of illness on P300 were
assessed using regression analysis.
Results: P300 amplitude showed no age-related decrease in either group; how
ever, among schizophrenic participants, P300 amplitude correlated positivel
y with onset age and negatively with illness duration. P300 latency correla
ted positively with age in schizophrenic participants and also tended to in
crease with age in controls. Slopes of the latency-age relationships were s
ignificantly greater in schizophrenic participants than in control particip
ants. Latency also correlated positively with illness duration but showed n
o relationship to onset age.
Conclusions: P300 amplitude and latency are reduced and delayed with longer
illness duration in schizophrenia, consistent with a progressive pathophys
iological process. Reduced P300 amplitude may also be a marker of an early
onset variant of schizophrenia. (C) 2000 Society of Biological Psychiatry.