Composite versus multiple-rating scales in the assessment of psychopathology in people with mental retardation.

This study tested the hypothesis that separate ratings of frequency and duration add significant information to ratings of problem severity in the assessment of psychopathology in people with mental retardation. The Reiss Screen was modified to require ratings of problem severity, frequency and duration for each of 38 maladaptive behaviours. The 171 adolescents and adults were rated by caretakers and supervisory staff on the modified Reiss Screen. The three ratings were found to be very highly intercorrelated. Moreover, multiple linear regression analyses revealed that the ratings of frequency and duration did not add significant information to that provided by ratings of problem severity in the prediction of psychiatric diagnosis in the person's case file. The results support the use of composite scaling over multiple-ratings in the assessment of psychopathology in persons with mental retardation.