ABSTRACT

Impairment of intellectual function, particularly in a forensic context, should be assessed using an individually administered, reliable and valid, standardized test, such as the third edition of the Wechsler Adult Intelligence Scale. Mental health legislation in England and Wales, Scotland, and Northern Ireland may apply to people with intellectual disability as well as to people with mental illness or personality disorder, and this is generally true in most countries around the world. People with intellectual disability have a high prevalence of psychiatric disorders, including mental illness, other pervasive developmental disorders and/or neuropsychiatric disorders related to the cause of their brain damage. Pervasive developmental disorders, especially autism, are common among adults with intellectual disability. As intellectual disability from childhood is generally explained by very early brain damage, developmental disorders or a combination of the two, a range of neuropsychiatric disorders is common among adults with intellectual disability, epilepsy among them.