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What is `mental illness`?

Definitions of mental illness are notoriously difficult to draft. If they are framed too narrowly they deny services to people. If they are too broad they may result in unnecessary intervention.³

Mental health problems and mental illness refer to a range of cognitive, emotional and behavioural disorders that interfere with the lives and productivity of people. There is, however, no one single definition of mental illness, as definitions vary across jurisdictions and professions. In determining an appropriate definition of mental illness for the Project, we have taken into consideration legal, clinical and social approaches to defining mental illness.

Legal definitions of mental illness

Under Mental Health Act 1990 (NSW) sch. 1, “mental illness” is defined as a condition characterised by the presence of symptoms such as delusions, hallucinations, serious disorder of thought form, a severe disturbance of mood, or sustained or repeated irrational behaviour, which seriously impairs, either temporarily or permanently, the mental functioning of a person.⁶ A “mentally ill person” is someone who suffers a mental illness where, owing to that illness, there are reasonable grounds for believing that care, treatment or control of the person is necessary, for their own or others’ protection. This determination must take into account the person’s continuing condition, including the effects of any likely deterioration in their condition.⁷

It is noteworthy that the above-named symptoms, listed in the Mental Health Act 1990 (NSW), are most often associated with a diagnosis of psychosis, a particular and more severe form of mental illness. Other more common mental illnesses such as anxiety disorders, depression and substance abuse may not necessarily fit the definition provided in this Act.⁸

Clinical definitions of mental illness

Because the focus of clinical practice is on prevention and control of mental illness through treatment, clinical definitions of mental illness are far broader than their legal counterparts. It is rare to find a single definition in the clinical setting: in this context, a definitive statement about what is mental illness is often less helpful than determining how a disorder should be classified and treated.

Accordingly, there are two main international medical standards used in the classification of mental illness. The first of these is the World Health Organisation’s International Classification of Diseases (ICD-10), last revised in 1992 and used predominantly in Europe. The ICD-10 defines “mental disorder” as “a general term which implies the existence of a clinically recognisable set of symptoms or behaviour associated … with … interference with personal functions”.⁹

The second international standard is the American Psychiatric Association’s Diagnostic and Statistical Manual of Mental Disorders (DSM-IV), revised in 2000 and used more frequently in the UK and the US. According to this system, a “mental disorder” must comprise a manifestation of “behavioural, psychological, or biological dysfunction in the individual”. It is:

a clinically significant behavioural or psychological syndrome or pattern that occurs in an individual and that is associated with present distress … or disability … or with a significantly increased risk of suffering death, pain, disability, or an important loss of freedom …¹⁰

Both classification systems have been adopted by key Australian agencies. The Australian Bureau of Statistics (ABS) has used an adapted version of the ICD-10 for its surveys (such as the 2001 National Health Survey (NHS)).¹¹ In the National Mental Health Plan 2003–08,¹² both the ICD-10 and DSM-IV classification systems are cited.

The Commonwealth Department of Health and Aged Care’s Mental Health Branch makes the further distinction of classifying mental illnesses as either psychotic—including schizophrenia and some forms of depression—or non-psychotic—including phobias, anxiety, some forms of depression, eating disorders, physical symptoms involving tiredness or pain, and obsessive-compulsive disorder.¹³

Social definitions of mental illness

The term ‘psychiatric disability’ is a narrower term than mental illness, as not all people with a mental illness will consider themselves, or be considered, to have a psychiatric disability. This is reflected, for example, in the Disability Services Act 1986 (Cth), where the very narrow definition of “disability” is restricted to those conditions which are “permanent or likely to be permanent”.

Nevertheless, it is important to consider the social model of disability, which though subject to constant evolution, is largely preferred by disability advocates. While not denying the individual’s limitations, the social model understands disability as a function of “society’s failure to provide appropriate services and adequately ensure the needs of disabled people are fully taken into account in its social organisation”.¹⁴ This is in contrast to “official” definitions, which locate disability in the individual’s pathology or biology.¹⁵ One important Australian study which applied the social model was the Disability Council of NSW’s (Disability Council) 2003 A Question of Justice report.¹⁶ Here, the model was used to “shift the focus from issues of individual impairment to issues of systemic disablement”, identifying as the source of disability not impairment itself, but socially and economically constructed discrimination and exclusion, that is, the responses of society towards impairment. Carney suggests that the social model has now gained wide acceptance within disability literature, with policy also moving away from the traditional medical model and towards a more nuanced understanding, whereby the emphasis is on “participation” rather than “impairment”.¹⁷

Working definition of mental illness for this project

Although the DSM-IV is somewhat more commonly used in clinical settings in Australia, the Project has adopted the ICD-10 definition, which is used by the ABS and so enables the use of ABS data. The Project did not adopt the Mental Health Act 1990 (NSW) definition due to its more limited scope.

Of particular interest to the Project were the disorders with the highest prevalence in Australia and NSW, namely, anxiety disorders, affective disorders and substance use disorders. As the next section indicates, a significant number of people in NSW are affected by these disorders. Recent literature has focused on the social and economic disadvantages that those suffering from these disorders can face.¹⁸ Despite their lower prevalence, psychotic disorders were also of interest, given their strong association with high levels of social, economic and, at times, physical disadvantage.¹⁹ While the above-named disorders were of particular interest, no mental illnesses were excluded from our study. In accordance with the design of this research, those we interviewed and consulted were free to raise whichever mental illnesses they felt were relevant.

In summary, for the purposes of the Access to Justice and Legal Needs of People with Mental Illness Project, ‘mental illness’ means the existence of a clinically recognisable set of symptoms or behaviour associated in most cases with distress and with interference with personal functions.²⁰ While not an exhaustive list, the following clinically recognisable disorders were of particular interest in our study:

• Anxiety disorders: social phobia, agoraphobia, panic disorder, generalised anxiety disorder, obsessive-compulsive disorder, and post-traumatic stress disorder.
• Affective disorders: major depressive disorder (depression), dysthymia, mania, hypomania, and bipolar mood disorder.
• Substance use disorders: alcohol and drug abuse and dependence.
• Psychotic disorders: schizophrenia and substance-induced psychotic disorders.

In conjunction with this definition, the social model of disability—explained above—was also drawn upon. This model allows for an understanding of the social and environmental factors that contribute to the lived experience of people with these disorders.²¹