Longitudinal, prospective evaluations of intelligence in children at risk

Data are presented from the intellectual assessment of 153 children at two test periods in the St. Louis Risk Research Project. At phase I (1967-72) the Wechsler tests of intelligence were administered to offspring in families with one schizophrenic parent, one parent with affective disorder, one parent with schizoaffective disorder, one physically ill parent, or to offspring with two normal parents (mean age, 8 years). At phase II (1975-78) the intelligence of offspring was tested again at a mean age of 16 years. Differences between children as a function of parental diagnoses were assessed using a repeated measures analysis of covariance. The analyses yielded significant time effects. A time-by-parental-diagnosis effect was found for Verbal IQ, with children of parents with schizophrenia, affective disorder, or physical illness all showing a greater decrease in their scores at the second testing than offspring in the other groups. Offspring of psychotic mothers had lower IQ scores than those of psychotic fathers. Children of schizophrenics and children of schizoaffectives had the lowest stability in IQ scores from the first to the second testing.