ABSTRACT
Among the controversies that concern clinicians working with adults with intellectual disability (ID), perhaps two in particular stand out as special challenges.
The ®rst lies with the now historic separation of ID from mental illness, establishing the concept of `dual diagnosis' (Reiss 1990) and, by implication, a duality of service provision for those in need: on the one hand rest the educational and social vulnerabilities that constitute the disability itself (as opposed to the impairment) and on the other the multifaceted emotional and behavioural consequences of ID that, in some individuals and under some circumstances, appear to constitute an additional and, crucially, separable mental disorder. The question arises: if such a distinction can be established in principle, to what extent can it be reliably discerned in practice (Sturmey 1999)?
