Nigel Turner's HyperGUIDE to the Mental Health Act

Attempts to Define Mental Illness

The Common Sense Approach

In the absence of any clear definition in law, a court will tend to view the term "Mental Illness" in terms of what a sensible member of the public would make of those words. In practice, it is a doctor who has to certify, when appropriate, that someone has a Mental Illness and the doctor is using a body of academic and practical knowledge in reaching her or his decision on this.

A Government Attempt

The Department of Health once published the following description of "Mental Illness":

Mental Illness means an illness having one or more of the following characteristics...

more than temporary impairment of intellectual functions shown by a failure of memory, orientation, comprehension or learning capacity;
more than temporary alteration of mood of such degree as to give rise to the patient having a delusional appraisal of his situation, his past or his future, or that of others or to the lack of any appraisal;
delusional beliefs, persecutory, jealous or grandiose;
abnormal perceptions associated with delusional misinterpretation of events;
thinking so disordered as to prevent the patient making a reasonable appraisal of his situation or having reasonable communication with others.

None of the above amounts to a formal legal definiton, and the lack of a formal definition makes Mental Illness unlike the other forms of Mental Disorder dealt with under the Section 1 Definitions.

Overview page. Contents page. Introduction page.

This page last revised 28 March 1996
While every effort has been made to ensure the accuracy and reliability of information in these pages, they are not intended to be relied upon as an authoritative statement of the law. The author cannot accept liability for errors or omissions.