The Prevalence of Mental Illness in People with Intellectual Disability Over 50 Years of Age, and the Diagnostic Importance of Information from Carers

Abstract

Issues are discussed concerning the mental health of people with intellectual disability (ID), focusing particularly on older individuals. Background information includes previously published prevalence figures, the importance of environmental influences and the ‘pathway’ to psychiatric care for people with ID. The latter issues serves to reinforce the importance of care staff in recognising potential symptoms of mental illness — the main focus of this paper. Figures for prevalence of mental disorder in people over 50 years of age with moderate, severe and profound ID are drawn from a study in which we developed and used a semistructured clinical interview specifically designed for use with intellectually disabled individuals: the ‘PAS-ADD’. Prevalence of diagnosable disorders was 11.4%, most of which were major depression and generalized anxiety. Prevalence of dementia was 11.4%, but much higher for people with Down’s syndrome (44%). Most of the cases (75%) were not receiving treatment for the condition. Carers gave generally high-quality information on the psychiatric status of their clients, this information often being crucial in coming to a diagnosis. However, they often did not recognise the significance of the symptoms, and lacked confidence to take the step of drawing the problem to the attention of the general physician. It is concluded that appropriate training of care staff in the awareness of mental illness symptoms would increase the proportion of intellectually disabled people receiving appropriate treatment.