The following document was written by Dr Satvir Singh FRANZCP (Aust), FRCPsych (UK), MSc (Lon), MRCPsych (UK), DPM, MBBS Consultant Psychiatrist & Lead Consultant for Undergraduate Medical Education (psychiatry) Kent & Medway NHS and Social Care Partnership Trust Canterbury, Kent in Dec 2007.
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A perfect clinical diagnosis would usually predict the possible underlying causative factor/s, the patho-physiology, clinical signs and symptoms, response to the treatment and the course of the illness. Such perfect diagnoses are possible in various infectious diseases and to an extent, in surgery. However, in General Medicine and in particular, in psychological medicine, this perfect concept of disease is not possible. This is because of our limited knowledge about the underlying causes of mental disorders and any other objective measurable standard tests. Probably, some organic brain disorders, such as Dementia of Alzheimer’s Type, Lewy Body Dementia and Vascular Dementia can be separated clinically, but to be definite about he diagnosis, one would have to rely on brain biopsy and more often on autopsy results.

A specific disease process is further understood and classified by the clinician by its consequences, such as the impairment, disability and handicaps that may be caused. However, in psychiatry, the ultimate consequences may be very similar despite the differing underlying psychological and biological processes.

In psychiatry, the concept of “disease” does not encompass all of the above. Hence the broad term of “disorder” is often in use and not “disease.”

Why Should we Classify Mental Disorders?

It is relevant and important to classify mental disorders for two very good reasons:

  1. To communicate with other health professionals on a day-to-day clinical level and also to carry out meaningful scientific research studies across the world.
  2. To communicate with our patients and their families.

Methods of Classification

There are two principle methods of classification categories that are in current use:

  1. In the UK and other European countries is the International Classification of Diseases (ICD-10; WHO 1992), which is most widely used and describes the internationally accepted glossary of categories of mental disorders with key sets of clinical features.
  2. While in the United States of America, Canada, Australia, New Zealand, India and China, the Diagnostic and Statistical Manual of Mental Disorders – Fourth Edition (DSM-IV; published by American Psychiatric Association, 1994) is most widely used

The DSM-IV is a multi-axial diagnostic system where there are 5 Axes, namely:

Axis – 1: Main clinical diagnosis, currently under review and is the focus of attention and treatment.

Axis – 2: Personality Type/Disorder, Learning Disability

Axis – 3: Physical Disorders/Conditions

Axis – 4: Psychosocial Stress Factors

Axis – 5: Functioning Level in the last 12 months

The ICD-10 (WHO, 1992) is single Axis, which is widely used, but it is also available in a different format, for use in Primary Care and for research with multi-axial system.

The ICD-10 guidelines and criteria do not include the social consequences of a disorder while DSM-IV includes impairment in social functions.

In both the systems, the main categories are as follows:

  1. Dementia Disorders (Organic Mental Disorders)
  2. Substance Abuse Disorders
  3. Schizophrenia and other Psychotic Disorders
  4. Mood (Affective) Disorders
  5. Stress Related Somatoform and Anxiety Disorders
  6. Behavioural Disorders associated with Physiological disturbances:
    • Eating Disorders
    • Sleep Disorders
    • Sexual & Gender Identity Disorders
  7. Personality Disorders
  8. Childhood & Adolescence Psychiatric Disorders
  9. Learning Disability Disorders
  10. Attention Deficit and Disruptive Behaviour Disorders

Dr Satvir Singh
FRANZCP (Aust), FRCPsych (UK), MSc (Lon), MRCPsych (UK), DPM, MBBS
Consultant Psychiatrist & Lead Consultant for Undergraduate Medical Education(psychiatry)
Kent & Medway NHS and Social Care Partnership Trust
Canterbury, Kent


  1. ICD-10, WHO 1992
  2. DSM-IV, APA 1994
  3. Companion to Psychiatric Studies, Eve C Johnstone, et al, 1998


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