Diagnosis of Mental and Behavioural Disorders

Introduction

Mental and behavioural disorders have been the object of many classifications, from the Greek Antiquity during which they were divided into mania, melancholia, phrenitis and lethargia, to the most recent diagnostic manual, the DSM-IV, published in 1994.

The purpose of medical classifications is to divide the population of patients into distinct and homogeneous sub-groups, by using as criteria the observed symptoms and, if it is known, their cause, in order to choose the most adequate therapy. The process leading to the attribution of a given patient to one of the subgroups constitutes the diagnosis. Sub-groups defined by a specific pattern of symptoms are called syndromes. The term disease is theoretically reserved to those defined by a common aetiology, although it has often been applied to purely syndromic entities. Today, psychiatry uses the more vague term Disorder for both. Several Syndromes may originate from the same cause and, conversely, a single syndrome may have diverse aetiologies.

Historical Perspective

The first general classification of mental disorders appeared in the second half of the 18th century. Its author, Boissier de Sauvages, had compiled all the descriptions proposed since Antiquity and presented them according to the formal structure introduced in the botanical classification by his friend Linnaeus. It had little influence on modern psychiatry which began around 1800 with Pinel. During the greatest part of the 19th century, the main contribution of the psychiatrist consisted in the accurate description of syndromes. They belonged mainly to those aspects of mental disorders later known as psychoses, which led to the commitment to asylums. Among the less severe psychological manifestations, the neuroses, a term coined by Cullen to emphasize what he considered to be their hypothetical aetiology: a dysfunction of the nervous system, and whose main forms were hysteria, hypochondriasis, and later neurasthenia, were studied by neurologists like Charcot and the character peculiarities, formerly the object of descriptions by writers and moralists, constituting today the personality disorders were incorporated into psychiatry only at the end of the century.

Between 1883 and 1917, in the eight successive editions of his Textbook, Kraepelin elaborated progressively the classification whose main outlines are the basis of the future ones. His aim was to describe separate diseases, each defined by its cause, its psychopathological mechanisms, and by its clinical manifestations. He postulated in each one a strict correspondence between the three levels. In most cases he had to evoke only hypothetical causes, but affirmed that, because of its postulates, the classification based on the clinical manifestations would not be modified when the aetiology would be later proved, provided that one would not only take into account the transversally observed symptoms, as in the syndromic perspective, but also ‘the developmental conditions, the course and the outcome of the individual disorder’. Kraepelin's classification distinguished four main groups of disorders:

• 1
  those whose origin was a proven anomaly of the brain structure, either acquired as in the dementias, or congenital as in mental retardation;
• 2
  the psychoses, for which the postulated and endogenous origin, possibly metabolic or hereditary, the isolation of their two main forms, Dementia pracox – later renamed by Bleuler Schizophrenia. And manicdepressive psychosis being the most often evoked contribution of Kraepelin;
• 3
  the neuroses of psychogenic nature; and
• 4
  the personality disorders, relatively permanent anomalies related to constitutional [Page 333]factors. In the following decades, many modifications were introduced in this general scheme, such as the expansion of the concept of neurosis under the growing influence of psychoanalysis.

Modern Classification Systems

Many of those modifications were restricted to a national or ideological school and this led to many difficulties to communication between specialists, even if they used the same terminology: the low-inter-raters reliability of the psychiatric diagnosis was demonstrated by many experimental studies. Efforts towards a consensus came mainly from two organizations. The World Health Organization (WHO) published periodically an International Classification of Diseases (ICD) which included a chapter on mental disorders. Initially, only an enumeration of the names of the disorders, it included only with its ninth revision (1975) a glossary giving a short description of the characteristics of each one. The American Psychiatric Association began in 1952 for the benefit of its members to publish a Diagnostic and Statistical Manual (DSM) which contained a glossary added to the terms recommended.

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