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Diagnostic manuals

October 2016

Position statement 77


Summary

Diagnostic manuals allow clinicians, teachers and researchers to ensure consistency in diagnosis. However, the complexity of patients’ presentations may not always fit neatly into diagnostic categories.

Purpose

The Royal Australian and New Zealand College of Psychiatrists (RANZCP) has developed this position statement in order to inform psychiatrists, trainees and the public of the position of the RANZCP with regard to the use of diagnostic manuals. This statement does not provide an opinion on the content or application of specific diagnostic manuals.

Key points

  • Diagnostic classification systems are used in clinical, educational, research and service settings. They are also used for funding purposes and affect the way services are delivered.
  • These classification systems outline a set of symptoms, and provide commentary, that have been agreed by experts to be a reasonable basis for defining the limits of categories in the classification of mental disorders.
  • The two main diagnostic classification systems are the Diagnostic and Statistical Manual of Mental Disorders (DSM) and the International Classification of Diseases (ICD).
  • Diagnostic manuals allow clinicians, teachers and researchers to ensure consistency in diagnosis.
  • Diagnostic manuals have limitations however. The complexity of patients’ presentations and the manifestation of disease may not always fit neatly into diagnostic categories.

Definition

Diagnostic classification systems are, most simply, a set of symptoms and comments that have been agreed by experts to be a reasonable basis for defining the limits of categories in the classification of mental disorders. In this statement the shorthand term diagnostic manual is used to refer to diagnostic classification systems. Two main diagnostic manuals are used to assist in diagnosing psychiatric illnesses:

  • The DSM is published by the American Psychiatric Association and covers all categories of mental disorders for both adults and children. The manual is non-theoretical and focused mostly on describing symptoms as well as statistics concerning which gender is most affected by the illness, the typical age of onset, the effects of treatment, and common treatment approaches. The DSM-5 was released in 2013 and is currently the most up-to-date edition.
  • The ICD is a standard diagnostic tool for epidemiology, health management and clinical purposes. It is used to classify diseases and other health problems and is often used in completing health and vital records including death certificates. The ICD includes a section on mental and behavioural disorders. The ICD-10 came into use in 1994 and at the time of writing was the most up-to-date edition. The ICD-11 is expected to be released in 2018.

The ICD was developed alongside the DSM and the two manuals seek to use the same codes. There are however significant differences in terms of categorisation of some disorders.

The use of diagnostic manuals

Diagnostic manuals allow clinicians and researchers to compare patients’ presentations with a standardised list of symptoms and criteria. This assists in arriving at consistent diagnoses and can also enable advances in psychiatric research. Diagnostic manuals are also a useful teaching resource.

Diagnostic manuals are also used more broadly; insurance companies and legal proceedings may require diagnoses made using specific criteria such as those in the DSM. Such manuals can also have broader implications as to how society views mental disorders and behaviour.

Limitations and cautionary notes

There are limitations to the use of diagnostic manuals. Many clinicians argue that the complexity of patients’ presentations cannot be adequately summarised by limited diagnostic codes. Other limitations can be that the categories do not reflect natural disease boundaries, patients may present with symptoms meeting criteria for more than one disorder and that diagnostic manuals do not take account of the cultural and social determinants of mental health. For instance, many clinicians argue that the language of the diagnostic criteria used in the manuals is not adequately adapted to the needs of populations such as Indigenous peoples and the cultural and social contexts that may affect their mental health. For these reasons, when using diagnostic manuals clinicians should bear in mind their controversial nature and potential limitations.

Both the ICD and the DSM provide cautionary notes about their use. The following extract from the DSM-5 summarises some of the key issues:

Since a complete description of the underlying pathological processes is not possible for most mental disorders, it is important to emphasize that the current diagnostic criteria are the best available description of how mental disorders are expressed and can be recognized by trained clinicians.

Use of DSM-5 to assess for the presence of a mental disorder by nonclinical, nonmedical, or otherwise insufficiently trained individuals is not advised. It is also important to note that the DSM-5 does not provide treatment guidelines for any given disorder.

The use of DSM-5 should be informed by an awareness of the risks and limitations of its use in forensic settings. When DSM-5 categories, criteria, and textual descriptions are employed for forensic purposes, there is a risk that diagnostic information will be misused or misunderstood. In most situations, the clinical diagnosis of a DSM-5 mental disorder such as intellectual disability (intellectual development disorder), schizophrenia, major neurocognitive disorder, gambling disorder, or paedophilic disorder does not imply that an individual with such a condition meets the legal criteria for the presence of a mental disorder or a specified legal standard (e.g. for competence, criminal responsibility, or disability). Additional information is usually required beyond that contained in the DSM-5 diagnosis, which might include information about the individual’s functional impairments and how these impairments affect the particular abilities in question.

Recommendations

  • While diagnostic manuals are an important tool, psychiatrists should be aware of the limitations of use.
  • Individual psychiatrists should use their appropriate clinical and professional knowledge to determine diagnosis of mental disorders. While diagnostic manuals can be used as tools to assist in diagnosis, there is no requirement to use such tools or form a diagnosis based on them.
  • In legal settings, diagnostic manuals should be used with caution, if at all, with regard to their limitations and the fact that inclusion of a diagnostic category does not imply that the condition meets legal or other nonmedical criteria for what constitutes a mental disorder.
  • Only those who have received specialised training and possess sufficient experience are qualified to diagnose and treat mental illnesses. Laypersons should consult diagnostic manuals only to obtain information, not to make diagnoses.
  • Diagnostic manuals reflect a current consensus at a point in time and should be updated within appropriate timeframes based on scientific progress and experience with the use of the manuals.

 

Responsible committee: Practice, Policy and Partnerships Committee

World Health Organization (1990) ICD-10 Classifications of Mental and Behavioural Disorders: Clinical Descriptions and Diagnostic Guidelines. Geneva, Switzerland: WHO.

American Psychiatric Association (2013) Diagnostic and Statistical Manual of Mental Disorders (5th edition) Washington DC, USA: APA.


Disclaimer: This information is intended to provide general guidance to practitioners, and should not be relied on as a substitute for proper assessment with respect to the merits of each case and the needs of the patient. The RANZCP endeavours to ensure that information is accurate and current at the time of preparation, but takes no responsibility for matters arising from changed circumstances, information or material that may have become subsequently available.