Classification is a process by which phenomena are organized into categories so as to bring together those phenomena that most resemble each other and to separate those that differ. Any classification of psychiatric disorders, like that of medical illnesses, should ideally be based on aetiology. For a large majority of psychiatric disorders, no distinct aetiology is known at present, although there are many attractive probabilities for several of them. Therefore, one of the most rational ways to classify psychiatric disorders at present is probably syndromal. A syndrome is defined as a group of symptoms and signs that often occur together, and delineate a recognisable clinical condition.
The syndromal approach of classifying psychiatric disorders, on the basis of their clinical signs and symptoms, is very similar to the historical approach of classification of medical illnesses, when aetiology of a majority of medical illnesses was still obscure.
There are three major purposes of classification of psychiatric disorders:
- To enable communication regarding the diagnosis of disorders,
- To facilitate comprehension of the underlying causes of these disorders, and
- To aid prediction of the prognosis of psychiatric disorders.
This syndromal approach of classification, in the absence of clearly known aetiologies, fulfils these purposes reasonably well.
Before proceeding to look at current classifications of psychiatric disorders, it is important to define what is meant by the term, psychiatric disorder.
DEFINITION OF A PSYCHIATRIC DISORDER
The simplest way to conceptualize a psychiatric disorder is a disturbance of Cognition (i.e. Thought), Conation (i.e. Action), or Affect (i.e. Feeling), or any disequilibrium between the three domains. However, this simple definition is not very useful in routine clinical practice.
Another way to define a psychiatric disorder or mental disorder is as a clinically significant psychological or behavioural syndrome that causes significant (subjective) distress, (objective) disability, or loss of freedom; and which is not merely a socially deviant behaviour or an expected response to a stressful life event (e.g. loss of a loved one). Conflicts between the society and the individual are not considered psychiatric disorders. A psychiatric disorder should be a manifestation of behavioural, psychological, and/or biological dysfunction in that person (Definition modified after DSM-IV-TR, APA).
Although slightly lengthy, this definition defines a psychiatric disorder more accurately.
NORMAL MENTAL HEALTH
According to the World Health Organization (WHO), Health is a state of complete physical, mental and social well-being, and not merely absence of disease or infirmity.
Normal mental health, much like normal health, is a rather difficult concept to define. There are several 2models available for understanding what may constitute ‘normality’ (see Table 1.1).
Although, normality is not an easy concept to define, some of the following traits are more commonly found in ‘normal’ individuals.
- Reality orientation.
- Self-awareness and self-knowledge.
- Self-esteem and self-acceptance.
- Ability to exercise voluntary control over their behaviour.
- Ability to form affectionate relationships.
- Pursuance of productive and goal-directive activities.
CLASSIFICATION IN PSYCHIATRY
Like any growing branch of Medicine, Psychiatry has seen rapid changes in classification to keep up with a conglomeration of growing research data dealing with epidemiology, symptomatology, prognostic factors, treatment methods and new theories for the causation of psychiatric disorders.
Although first attempts to classify psychiatric disorders can be traced back to Ayurveda, Plato (4th century BC) and Asclepiades (1st century BC), classification in Psychiatry has certainly evolved ever since.
At present, there are two major classifications in Psychiatry, namely ICD-10 (1992) and DSM-IV-TR (2000).
ICD-10 (International Classification of Diseases, 10th Revision, 1992) is World Health Organisation's classification for all diseases and related health problems (and not only psychiatric disorders).
Chapter ‘F’ classifies psychiatric disorders as Mental and Behavioural Disorders (MBDs) and codes them on an alphanumeric system from F00 to F99. ICD-10 is now available in several versions, the most important of which are listed in Table 1.2. There are several versions of ICD-10; some are listed in Table 1.3.
DSM-IV-TR (Diagnostic and Statistical Manual of Mental Disorders, IV Edition, Text Revision, 2000) is the American Psychiatric Association (APA)'s classification of mental disorders. DSM-IV-TR is a text revision of the DSM-IV which was originally published in 1994.
The next editions of ICD (ICD-11) and DSM (DSM-V) are likely to be available in the years 2012–14.
For the purpose of this book, it is intended to follow the ICD-10 classification. ICD-10 is easy to follow, has been tested extensively all over the world (51 countries; 195 clinical centres), and has been found to be generally applicable across the globe. At some places in the book, DSM-IV-TR diagnostic criteria are also discussed, wherever appropriate.
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Earlier classifications in psychiatry were based on hierarchies of diagnoses with presence of a diagnosis higher in the hierarchy usually ruling out a diagnosis lower in the hierarchy. This was felt to be in keeping with the teaching of Medicine at large at the time, where there was emphasis on making a single diagnosis of one disease rather than explaining different symptoms by different disease entities.
The presence of a diagnostic hierarchy implied that the conditions higher up in the hierarchy needed to be considered first, before making a diagnosis of those lower down in the hierarchy. For example, it was felt that a current diagnosis of organic mental disorder such as delirium would exclude a diagnosis of anxiety disorder in presence of agitation; and alcohol and drug induced disorders would take precedence over a diagnosis of primary mood disorder.
The current classifications however encourage recording of multiple diagnoses in a given patient (as co-morbidity) regardless of any hierarchy. Although a diagnostic hierarchy makes much clinical sense, consideration and recording of co-morbidity can be helpful in identifying more of patient's needs; for example, a diagnosis of co-morbid anxiety disorder 4in a patient with bipolar disorder helps identify and treat the anxiety component adequately.
MULTI-AXIAL CLASSIFICATION
The process of making a correct diagnosis is a very useful clinical exercise as evidence-based management can be dependent on making a correct diagnosis. However, sometimes making a clinical diagnosis can lead to labelling of patient and can be stigmatizing. This can also degrade the patient to “just another case” and does not direct attention to the whole individual.
In the last few decades, there has been an upsurge of interest in multi-axial systems for achieving a more comprehensive description of an individual's clinical problems and needs. The pattern adopted by DSM-IV-TR is a very good example of this attempt. In this system, an individual patient is diagnosed on five separate axes, ensuring a more through evaluation of needs (see Table 1.4).
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This method helps in making a more holistic, biopsychosocial assessment of an individual patient. Recently, ICD-10 has also brought out its own multi-axial classification version (see Table 1.3).