The use of factor analysis for ascertaining patterns of psychopathology in children with intellectual disability

The Developmental Behaviour Checklist (DBC) was developed to assess psychopathology in children with intellectual disabilities. A cut-off point between "non-cases' and "cases' was determined by comparison of the total scores with psychiatric clinical assessment. This paper describes a method aimed at determining the types of psychiatric problems in those regarded as "cases'. Factor analysis with varimax rotation carried out on a sample of 1093 subjects extracted six factors. Standardized factor scores were calculated for each subject in a community sample (n = 450), and the only or the dominant positive score was determined for each of the "cases'. Over 80% of "cases' could be allotted to one condition. Only a small number had none, or three or more conditions. The same procedure was replicated on a validation sample (n = 448) with even more satisfactory results. Differences in the prevalence of the six conditions by sex, age and level of mental retardation were ascertained. The validity and clinical relevance of this method are discussed.