Psychiatric Comorbidity in Older Adults with Intellectual Disability

The population of older adults with intellectual disability (ID) is large and growing due to a significant increase of life expectancy caused by improvements in health and social care. Multimorbidity is highly prevalent in this population and co-morbid psychiatric disorders are especially frequent.

The aim of this article is to review the prevalence and consequences of psychiatric comorbidity in the population of older adults with ID. We therefore performed a literature search of studies relevant to adults with ID, published since January 2006, using the following keywords: intellectual disability and comorbidity, intellectual disability and mental disorders, intellectual disability and polypharmacy.

Psychiatric comorbidity is frequent among patients with ID and correlates with older age. Mental disorders are present in up to 40% of older adults with ID and the most prevalent are challenging behaviour, depression, anxiety and dementia. Patients with ID and at least one co-morbid mental disorder are at a high risk of polypharmacy. Importantly, psychiatric comorbidity was found to significantly increase service use and costs of care.

Further investigation of the population of older adults with ID is needed, with special attention to development of clear treatment guidelines in order to effectively manage co-morbid mental illnesses and physical health problems.