P50 sensory gating deficit is a common marker of vulnerability to bipolar disorder and schizophrenia

Objective:  P50 gating in schizophrenia has contributed much to our understanding of the pathophysiology of the illness. We examined euthymic bipolar patients to determine if they also have a P50 gating deficit. Method:  P50 gating was measured in 81 euthymic bipolar patients (50 with a lifetime history of psychotic symptoms), 92 stable schizophrenic patients, and 67 control subjects. Results:  P50 gating was significantly lower in control subjects than in bipolar patients with a lifetime history of psychosis (P = 0.001) and schizophrenic patients (P = 0.0001). In all patient groups, the percentage of patients with P50 gating was higher than in the control group (χ2 = 30.596; P < 0.0001). There was no statistically significant correlation between P50 gating and other clinical variables. Conclusion:  Our data suggest that P50 gating deficit is a neurobiological marker that is present in stable schizophrenic patients and euthymic bipolar patients.