Childhood cognitive functioning in schizophrenia patients and their unaffected siblings: A prospective cohort study

While it is known that children of schizophrenia parents perform more poorl y on tests of cognitive functioning than children of normal parents, less c ertain is the degree to which such deficits predict schizophrenia outcome, whether cognitive functioning deteriorates during childhood in preschizophr enia individuals, and whether nongenetic etiologic factors (such as obstetr ic complications) contribute to these deficits. In the present study, 72 pa tients with schizophrenia or schizoaffective disorder, 63 of their siblings not diagnosed with schizophrenia, and 7,941 controls with no diagnosis wer e ascertained from a birth cohort whose members had been evaluated with sta ndardized tests of cognitive functioning at 4 and 7 years of age. Adult psy chiatric morbidity was ascertained via a longitudinal treatment data base i ndexing regional public health service utilization, and diagnoses mere made by review of all pertinent medical records according to DSM-IV criteria. B oth the patients with schizophrenia and their unaffected siblings performed significantly worse than the nonpsychiatric controls (but did not differ f rom each other) on verbal and nonverbal cognitive tests at 4 and 7 years of age. Preschizophrenia cases and their siblings were increasingly overrepre sented across decreasing quartiles of the performance distributions. There was not significant intra-individual decline, and there were no significant relationships between obstetric complications and test performance among t he preschizophrenia subjects. These results suggest that during the period from age 4 to age 7 years, premorbid cognitive dysfunction in schizophrenia represents a relatively stable indicator of vulnerability deriving from pr imarily genetic (and/or shared environmental) etiologic influences.