Under the Act, mental disorder is defined as "any disorder or disability of mind".

No matter the transgressions of the moment, the physical or psychic wounds, the disabilities of mind or body, Nanny had a delectably single-minded philosophy.

The Act covers mental disorder, i.e. 'mental illness, arrested or incomplete development of mind, psychopathic disorders or any other disorder or disability of mind'.

Rampton Hospital houses about 400 patients who have been detained under the Mental Health Act 1983 under the criteria of Mental Disorder (any disorder or disability of mind).

In the United Kingdom, "Psychopathic Disorder" was legally defined in the Mental Health Act (UK) as, "a persistent disorder or disability of mind (whether or not including significant impairment of intelligence) which results in abnormally aggressive or seriously irresponsible conduct on the part of the person concerned."