Schizophrenics with small P300: a subgroup with a neurodevelopmental disturbance and a high risk for tardive dyskinesia?

Schizophrenics with a neurodevelopmental disturbance resulting in micro- and macroanatomical cortical abnormalities are supposed to form a subgroup clinically characterized by low premorbid adjustment, early onset, incomplete remission, poor outcome, male predominance and high risk for tardive dyskinesia. A small amplitude of the event-related P3 (P300) potential could be a marker of this subgroup, because the cortical neurons and their orderly laminar arrangement are crucial for the electrogenesis of P3. In a 2-year follow-up study, auditory evoked P3 was recorded in 89 stabilized schizophrenic outpatients. Patients who developed tardive dyskinesia during the follow-up had smaller P3 than matched controls. Furthermore, a small P3 was associated with low premorbid adjustment, pronounced residual symptoms, low relapse rate, and male predominance. These findings indicate that schizophrenic patients with a reduced P3 have a higher risk of developing tardive dyskinesia and correspond clinically to a schizophrenic subgroup with a supposedly neurodevelopmental disturbance.