ICD-10 is larger than ICD-9. Numeric codes (001-999) were used in ICD-9, whereas an alphanumeric coding scheme, based on codes with a single letter followed by two numbers at the three-character level (A00-Z99), has been adopted in ICD-10. This has significantly enlarged the number of categories available for the classification. Further detail is then provided by means of decimal numeric subdivisions at the four-character level.
The chapter that dealt with mental disorders in ICD-9 had only 30 three-character categories (290-319); Chapter V (F) of ICD-10 has 100 such categories. A proportion of these categories have been left unused for the time being, so as to allow the introduction of changes into the classification without the need to redesign the entire system.
ICD-10 as a whole is designed to be a central ("core") classification for a family of disease and health related classifications. Some members of the family of classifications are derived by using a fifth or even sixth character to specify more detail. In others, the categories are condensed to give broad groups suitable for use, for instance, in primary health care or general medical practice. There is a multiaxial presentation of Chapter V (F) of ICD-10 and a version for child psychiatric practice and research. The "family" also includes classifications that cover information not contained in the ICD, but having important medical or health implications, e.g. the classification of impairments, disabilities and handicaps, the classification of procedures in medicine, and the classification of reasons for encounter between patients and health workers.
Definition Differences
Neurosis and psychosis
The traditional division between neurosis and psychosis that was evident in ICD-9
(although deliberately left without any attempt to define these concepts) has not been used in ICD-10. However, the term "neurotic" is still retained for occasional use and occurs, for instance, in the heading of a major group (or block) of disorders F40-F48, "Neurotic, stress-related and somatoform disorders". Except for depressive neurosis, most of the disorders regarded as neuroses by those who use the concept are to be found in this block, and the remainder are in the subsequent blocks. Instead of following the neurotic-psychotic dichotomy, the disorders are now arranged in groups according to major common themes or descriptive likenesses, which makes for increased convenience of use.
For instance, cyclothymia (F34.0) is in the block F30-F39, Mood [affective] disorders, rather than in F60-F69, Disorders of adult personality and behaviour; similarly, all disorders associated with the use of psychoactive substances are grouped together in F10-F19, regardless of their severity.
"Psychotic" has been retained as a convenient descriptive term, particularly in F23, Acute and transient psychotic disorders. Its use does not involve assumptions about psychodynamic mechanisms, but simply indicates the presence of hallucinations, delusions, or a limited number of severe abnormalities of behaviour, such as gross excitement and overactivity, marked psychomotor retardation, and catatonic behaviour.
All disorders attributable to an organic cause are grouped together in the block F00-F09, which makes the use of this part of the classification easier than the arrangement in the ICD-9.
The new arrangement of mental and behavioural disorders due to psychoactive substance use in the block F10-F19 has also been found more useful than the earlier system. The third character indicates the substance used, the fourth and fifth characters the psychopathological syndrome, e.g. from acute intoxication and residual states; this allows the reporting of all disorders related to a substance even when only three-character categories are used.
The block that covers schizophrenia, schizotypal states and delusional disorders (F20-F29) has been expanded by the introduction of new categories such as undifferentiated schizophrenia, postschizophrenic depression, and schizotypal disorder. The classification of acute short-lived psychoses, which are commonly seen in most developing countries, is considerably expanded compared with that in the ICD-9.
Classification of affective disorders has been particularly influenced by the adoption of the principle of grouping together disorders with a common theme. Terms such as "neurotic depression" and "endogenous depression" are not used, but their close equivalents can be found in the different types and severities of depression now specified (including dysthymia (F34.1)).
The behavioural syndromes and mental disorders associated with physiological dysfunction and hormonal changes, such as eating disorders, nonorganic sleep disorders, and sexual dysfunctions, have been brought together in F50-F59 and described in greater detail than in ICD-9, because of the growing needs for such a classification in liaison psychiatry.
Block F60-F69 contains a number of new disorders of adult behaviour such as pathological gambling, fire-setting, and stealing, as well as the more traditional disorders of personality.
Disorders of sexual preference are clearly differentiated from disorders of gender identity, and homosexuality in itself is no longer included as a category.
Differences on Disorders with onset specific to childhood
F80-F89 Disorders of psychological development Disorders of childhood such as infantile autism and disintegrative psychosis, classified in ICD-9 as psychoses, are now more appropriately contained in F84.-, pervasive developmental disorders. While some uncertainty remains about their nosological status, it has been considered that sufficient information is now available to justify the inclusion of the syndromes of Rett and Asperger in this group as specified disorders. Overactive disorder associated with mental retardation and stereotyped movements (F84.4) has been included in spite of its mixed nature, because evidence suggests that this may have considerable practical utility.
F90-F98 Behavioural and emotional disorders with onset usually occurring in childhood and adolescence
Hyperkinetic disorder is now defined more broadly in ICD-10 than it was in ICD-9. The ICD-10 definition is also different in the relative emphasis given to the constituent symptoms of the overall hyperkinetic syndrome; since recent empirical research was used as the basis for the definition, there are good reasons for believing that the definition in ICD-10 represents a significant improvement.
Hyperkinetic conduct disorder (F90.1) is one of the few examples of a combination category remaining in ICD-10, Chapter V (F). The use of this diagnosis indicates that the criteria for both hyperkinetic disorder (F90.-) and conduct disorder (F91.-) are fulfilled.
These few exceptions to the general rule were considered justified on the grounds of clinical convenience in view of the frequent coexistence of those disorders and the demonstrated later importance of the mixed syndrome.
Oppositional defiant disorder (F91.3) was not in ICD-9, but has been included in ICD-10 because of evidence of its predictive potential for later conduct problems. There is, however, a cautionary note recommending its use mainly for younger children.
The ICD-9 category 313 (disturbances of emotion specific to childhood and adolescence) has been developed into two separate categories for ICD-10, namely emotional disorders with onset specific to childhood (F93.-) and disorders of social functioning with onset specific to childhood and adolescence (F94.-). This is because of the continuing need for a differentiation between children and adults with respect to various forms of morbid anxiety and related emotions. The frequency with which emotional disorders in childhood are followed by no significant similar disorder in adult life, and the frequent onset of neurotic disorders in adults are clear indicators of this need. The key defining criterion used in ICD-10 is the appropriateness to the developmental stage of the child of the emotion shown, plus an unusual degree of persistence with disturbance of function. In other words, these childhood disorders are significant exaggerations of emotional states and reactions that are regarded as normal for the age in question when occurring in only a mild form. If the content of the emotional state is unusual, or if it occurs at an unusual age, the general categories elsewhere in the classification should be used.
In spite of its name, the new category F94.- (disorders of social functioning with onset specific to childhood and adolescence) does not go against the general rule for ICD-10 of not using interference with social roles as a diagnostic criterion. The abnormalities of social functioning involved in F94.- are of a limited number and contained within the parent-child relationship and the immediate family; these relationships do not have the same connotations or show the same cultural variations as those formed in the context of work or of providing for the family, which are excluded from use as diagnostic criteria.
Users of blocks F80-F89 and F90-F98 also need to be aware of the contents of the neurological chapter of ICD-10 (Chapter VI (G)). This contains syndromes with predominantly physical manifestations and clear "organic" etiology, of which the Kleine-Levin syndrome (G47.8) is of particular interest to child psychiatrists.
Terminology differences
Disorder
The term "disorder" is used throughout the classification, so as to avoid even greater problems inherent in the use of terms such as "disease" and "illness". "Disorder" is not an exact term, but it is used here to imply the existence of a clinically recognizable set of symptoms or behaviour associated in most cases with distress and with interference with personal functions. Social deviance or conflict alone, without personal dysfunction, should not be included in mental disorder as defined here.
Psychogenic and psychosomatic
The term "psychogenic" has not been used in the titles of categories, in view of its different meanings in different languages and psychiatric traditions. It still occurs occasionally in the text, and should be taken to indicate that the diagnostician regards obvious life events or difficulties as playing an important role in the genesis of the disorder.
"Psychosomatic" is not used for similar reasons and also because use of this term might be taken to imply that psychological factors play no role in the occurrence, course and outcome of other diseases that are not so described.
Disorders described as psychosomatic in other classifications can be found in;
F45.- somatoform disorders
F50.- eating disorders
F52.- sexual dysfunction
F54.- psychologicalor behavioural factors associated with disorders or diseases classified elsewhere
It is particularly important to note category F54.- (category 316 in ICD-9) and to remember to use it for specifying the association of physical disorders, coded elsewhere in ICD-10, with an emotional causation.
A common example would be the recording of psychogenic asthma or eczema by means of both F54 from Chapter V (F) and the appropriate code for the physical condition from other chapters in ICD-10.
Dissociative and somatoform disorders, in relation to hysteria
The term "hysteria" has not been used in the title for any disorder in Chapter V (F) of ICD-10 because of its many and varied shades of meaning. Instead, "dissociative" has been preferred, to bring together disorders previously termed hysteria, of both dissociative and conversion types. This is largely because patients with the dissociative and conversion varieties often share a number of other characteristics, and in addition they frequently exhibit both varieties at the same or different times. It also seems reasonable to presume that the same (or very similar) psychological mechanisms are common to both types of symptoms.
Two categories that have been included here but were not present in ICD-9 are F68.0, elaboration of physical symptoms for psychological reasons, and F68.1, intentional production or feigning of symptoms or disabilities, either physical or psychological [factitious disorder]. Since these are, strictly speaking, disorders of role or illness behaviour, it should be convenient for psychiatrists to have them grouped with other disorders of adult behaviour. Together with malingering (Z76.5), which has always been outside Chapter V of the ICD, the disorders from a trio of diagnoses often need to be considered together. The crucial difference between the first two and malingering is that the motivation for malingering is obvious and usually confined to situations where personal danger, criminal sentencing, or large sums of money are involved.
Source World Health Organization (WHO)
