An empirical test of the two-threshold model of disease transmission

Recent research on diabetes mellitus has revealed the existence of at least two independent subtypes. The multifactorial analysis method suggested by Reich & co-workers (1972) for testing the independence of transmission between subtypes of a complex disorder agrees with this distinction. These techniques were also sensitive to the non-unitary nature of the mental retardation within a sample of subjects drawn from the data set of Reed & Reed (1965). Therefore, we believe that this analysis could be a valuable adjunct to the limited repertoire of methods currently available to psychiatric researchers for dealing with issues of differential diagnosis.