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 ...