Measuring Behaviour Disorder in Mental Handicap

Abstract

By use of latent-trait item analysis (the Rasch model), the internal validity of the behaviour section of the MRC-HBS schedule was analysed. The set of behavioural symptoms in this rating scale was found to measure a one-dimensional structure. Thus addition of item scores provides a meaningful index. Such a numerical measure for the degree of behaviour disorder facilitates comparison between different patients or groups, and furthermore, forms the basis for quantitative description of the outcome of therapeutic intervention. A diagnosis of behaviour disorder was established in 17.2% of 302 mentally-handicapped adults. However, some kind of deviant behaviour was found in 41%, and was correlated with origin and degree of retardation, epilepsy, and place of living. The distribution of the symptoms strongly indicates that organic brain damage is a major aetiological cause.