In this review we explore the clinical and scientific status of
categorical models of childhood
disorder. Three themes are developed. First, the practical origins of standardised
category-based diagnostic schemes are examined along with their contemporary
philosophical and
psychological significance. Next, the impact that these systems have had
on the science of
child psychopathology is explored. We look at their link to the medical
model and the
assumption that childhood disorders are categorical, endogenous, and dysfunctional
in
nature. We argue that these assumptions underpin the dominant paradigm
in child
psychopathology and so constrain empirical study and theory development.
In the final
section, the different ways in which researchers have responded to this
link and its impact on
science are presented. We present the sort of scientific realism associated
with Meehl (1995)
as the most appropriate basis for a philosophically respectable child psychopathology.
Following this approach means unpacking the paradigmatic assumptions, including
the
assumption of the categorical structure of disorder, into hypotheses that
are then put to
empirical test. The sorts of data that would allow us to test the categorical
hypothesis are
identified. We conclude by discussing the results from three recent studies
using behaviour
genetic analysis of twin data that, in fact, lead us toward a rejection
of this hypothesis. The
implications for diagnostic and clinical practice of such a rejection are
discussed.