Poor P50 suppression among schizophrenia patients and their first-degree biological relatives

Objective: This study's goal was to replicate the finding that family members of schizophrenia patients show poor P50 suppression during a paired-click auditory evoked response paradigm. Method: The paired-click paradigm was used to test 44 schizophrenia patients, 60 of their clinically unaffected first-degree relatives, and 45 normal subjects. Two clicks (83 dB[A] over a 60-dB[A] white noise background) separated by 500 msec were presented 60 times to all subjects. P50 responses to the first and second clicks were selected from the digitally filtered data by using standard methods and the Ct recording site. Results: The schizophrenia patients had smaller P50 responses to click 1 than either their relatives or the normal subjects; the patients and their relatives, who did not significantly differ, had larger P50 responses to click 2 than the normal subjects. Schizophrenia patients had worse P50 suppression than either their family members or the normal subjects; the patients' family members had worse P50 suppression than the normal subjects. Conclusions: Family members of schizophrenia patients have worse P50 suppression than normal subjects. To the authors' knowledge, this is the first demonstration independent of the group associated with the University of Colorado that schizophrenia patients' family members have poor P50 suppression. This result is intrinsically important, perhaps especially because a recent report suggests genetic linkage of poor P50 suppression to the cholinergic receptor's alpha(7) nicotinic subunit.