Background: Although studies have detailed biological abnormalities in schizophrenia patients and their first-degree biological relatives, few studies have directly compared the utility of biological indices in these individuals.
Methods: Measures of global smooth-pursuit ocular motor (OM) function, low frequency and alpha band electroencephalogram (EEG) power, and nonspecific fluctuations (NSF) in electrodermal activity and visibility of the plexus in the nailfold were collected from 136 schizophrenia patients and 67 of their first-degree biological relatives, 71 affective disorder psychotic patients and 68 of their first-degree biological relatives, and 169 nonpsychiatric comparison subjects. We conducted receiver operator characteristic (ROC) analyses to determine how well each index differentiated the patient groups and the groups of first-degree relatives.
Results: Smooth-pursuit ocular motor function, low frequency and alpha band EEG power, and nailfold plexus visibility differentiated schizophrenia patients from nonpsychiatric comparison subjects. Nailfold plexus visibility was the only measure that significantly differentiated schizophrenia patients from both nonpsychiatric controls and affective patients. Smooth-pursuit ocular motor function and the number of electrodermal nonspecific fluctuations differentiated relatives of schizophrenia patients from nonpsychiatric comparison subjects.
Conclusion: Increased nailfold plexus visibility may mark a process associated with abnormal brain development leading to schizophrenia. Smooth-pursuit dysfunction may mark genetic vulnerability that is relatively specific to schizophrenia.