The 63 children with infantile psychosis who attended the Maudsley Hospital between 1950 and 1958 were individually matched for age, sex, IQ and year of attendance with a control group of clinic children with non-psychotic disorders. Both groups were re-examined in 1963-1964 and given individual psychiatric, neurological, social and psychological assessments. The IQ of the psychotic children at first hospital attendance (mean age 5 years 11 months) was correlated highly (o.63-o.74) with the level of intelligence and social maturity at follow-up (mean age 15 years 7 months). The results for the controls were closely similar. The age of the child at initial testing, the sex, whether or not the onset of psychosis had been preceded by a short period of normal development, and the presence of organic brain pathology were all unrelated to individual changes in IQ. Children who had no useful speech when they were first tested, and children who had been cared for in long-stay institutions, tended to have an SQ at follow-up well below their initial IQ. There was a non-significant tendency for a similar trend in children with an IQ of 59 or less. Also, there was some suggestion that an IQ based on only a few sub-tests tended to give an overestimate of later functioning. Of the 19 children who were initially untestable, 18 were untestable on the Wechsler Scales at follow-up and had an SQ below 50. The only exception was a child who, although untestable, had an SQ of 60 when first seen. It was concluded that the IQ is a most useful predictor of later development in psychotic children.
A quarter of both the psychotics and the controls were reading at an eight-year level or better. The level of achievement in reading was correlated with IQ but in both groups the level of reading was somewhat below that expected on the basis of IQ and chronological age. It was suggested that inadequate schooling, language retardation, and disturbed behaviour all contributed to the educational retardation. Further provision of special schooling is indicated.