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Diagnostic classification systemsrichard Harrington

Abstractdiagnosis should be an aid to communication. Its main purpose is to

bring together illnesses that have the same features. Ideally, a diagnosis

should identify disorders with the same underlying aetiology, the same

course and the same response to treatment. However, most disorders

have a multifactorial causation, and most risk factors can lead to sev-

eral different types of disorder. accordingly, diagnosis and classification

of child psychopathology has increasingly focused on the presenting

features of the disorder rather than its aetiology. the main current

diagnostic schemes are ICd-10 and dSm-Iv. although the schemes differ

in many ways, their overall classifications are very similar. most children

with psychiatric problems have multiple difficulties. there are five broad

groupings of clinical psychiatric syndromes, the two most common

being disruptive behavioural disorders and emotional disorders. this

paper discusses the diagnosis of these syndromes as well as associated

medical conditions, abnormal psychosocial situations and psychosocial

disabilites.

Keywords child psychiatry; classification; diagnosis; disruptive behavioural

disorders

Purposes and limitations of diagnosis

Diagnosis should be an aid to communication. Its main purpose is to bring together illnesses that have the same features. Ideally, a diagnosis should identify disorders with the same underlying cause, the same course and the same response to treatment. How­ever, even in general medicine such an ideal is seldom achieved. Many of the most common problems, such as heart disease, have multiple causes. Moreover, a single ‘medical’ cause, such as smoking, may lead to many different disorders, each with different consequences in terms of morbidity and treatment.

Similar issues apply in child psychiatry. Most disorders have a multifactorial causation, and most risk factors can lead to sev­eral different types of disorder. Accordingly, the diagnosis and classification of child psychopathology has increasingly focused on the presenting features of the disorder rather than its aetio­logy. With a few exceptions (e.g. post­traumatic stress disorder), diagnoses tell us about the symptoms and signs of a disorder but

Richard Harrington MD MPhil FRCPsych was Professor of Child and

Adolescent Psychiatry and Chair of the Department of Child and

Adolescent Psychiatry at the University of Manchester, Manchester,

UK. Sadly, Professor Harrington died in 2004, but we are pleased to

reprint his contribution to the first edition.

pSYCHIatrY 7:6 23

not necessarily about its causes or treatment, which must be con­sidered separately. A diagnosis of conduct disorder, for example, will convey the clinical presentation but does not convey which of the different causes are most important, and therefore which treatment is most appropriate.

Classifications: ICD-10 and DSM-IV

The main current diagnostic schemes are the International Statis­tical Classification of Diseases­10 (ICD­10; WHO, 1993) and the Diagnostic and Statistical Manual of Mental Disorders­IV (DSM­IV; APA, 1994). Although the schemes differ in many ways, their overall classifications are very similar. ICD­10 has a clinical ver­sion (used in this contribution), which gives broad prototypic descriptions of disorders, and a research version, which lists clearly defined diagnostic criteria.

Both ICD­10 and DSM­IV classify psychopathology into cat­egories. While it is likely that most psychopathology in children is based on continuously distributed underlying liability, cate­gorical systems have particular merits. First, most clinical deci­sions are categorical in nature, so even if a dimensional approach were used it would be necessary to convert it into a categorical one using cut­off points. Second, diagnostic categories provide a simple summary of a large amount of information.

Clinical use of diagnostic criteria

Lists of diagnostic criteria have been a major step forward in improving agreement among clinicians and investigators. Never­theless, when using these schemes in clinical work a number of issues should be borne in mind. • Diagnostic criteria are no more than a consensus of current concepts in a field that is changing rapidly; diagnostic schemes are certain to change substantially in the future. • Many children who are significantly impaired by psychiatric problems do not meet diagnostic criteria. • Equally, it is quite common to find children who meet the cri­teria for a psychiatric diagnosis, but who are not suffering greatly from their symptoms and are not impaired. Indeed, when psychiat­ric disorders are diagnosed using symptom criteria alone, the rate of the disorder becomes implausibly high. It is important therefore that clinical judgement is used when applying the criteria – they were never meant to be applied rigidly in a ‘cookbook’ fashion.

Multiaxial diagnosisMost children with psychiatric problems have multiple difficul­ties. For example, a child with a behavioural problem may also have mental retardation (learning disabilities) and live in a home with much family discord. No single diagnostic term can describe all of these difficulties, yet it is essential to record all of them in the assessment. The multiaxial diagnostic scheme was devised to deal with this issue (the axes used are shown in Table 1). A diagnosis in this scheme records something about a child’s problems on all six axes, even if one or more of them is nega­tive. For instance, the diagnosis could be hyperkinetic syndrome (axis one), leading to moderate social disability (axis six) in a child with mild mental retardation (axis three), who suffers from epilepsy (axis four) and who comes from a family characteri­zed by discord (axis five). The child’s reading problems can be

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explained by his mental retardation; there is no specific reading retardation (axis two).

Clinical psychiatric syndromes

There are five broad groupings of clinical psychiatric syndromes (Table 2), the two most common being disruptive behavioural dis­orders and emotional disorders. However, many other problems do not fall into these broad diagnostic groupings, such as eating disorders (e.g. anorexia nervosa), and attachment disorders.

Disruptive behavioural disorders are characterized by abnor­mal behaviour that gives rise to social disapproval. In younger children such behaviour consists of tempers, aggression, and dis­obedience (oppositional behaviour). In older children and ado­lescents the category also includes law­breaking and behaviours such as stealing, truancy and running away (conduct disorder). The diagnosis of conduct disorder is unsatisfactory as it depends on social norms, but in spite of this it has proved useful because children with this disorder share many features. Conduct disorders

ICD-10 multiaxial diagnosis

Axis Feature of the child

one Clinical psychiatric syndrome (e.g. hyperkinetic

syndrome)

two Specific disorders of psychological development

(e.g. specific reading retardation)

three Intellectual level (e.g. mild mental retardation)

Four associated medical conditions (e.g. epilepsy)

Five associated abnormal psychosocial situations

(e.g. family discord)

Six Global assessment of psychosocial disability

(e.g. moderate social disability)

Table 1

pSYCHIatrY 7:6 23

are strongly associated with reading difficulties and often persist into adult life in the form of personality disorders.

Emotional disorders are those in which the main problem is an abnormality of emotions such as anxiety, depression, fear and obsessions. These disorders are sometimes referred to as ‘inter­nalizing’ disorders, as they are believed to be due to the inter­nalization of stress. However, this term is probably best avoided as these disorders are in fact multifactorial. Emotional disorders differ from other child psychiatric disorders in having an equal sex ratio. Indeed, after puberty the incidence of some emotional disorders, most notably depression, becomes more frequent in girls. It was thought that emotional disorders had a good adult prognosis, and early­onset cases often do. However, adolescent­onset cases often persist into adult life.

Hyperkinetic disorders are defined by the simultaneous pres­ence across situations of motor overactivity, impulsivity and in­attention. These disorders typically start before the age of 5 years and are strongly associated with conduct disorders. The outcome is similar to that of conduct disorder, but unlike conduct disorder there is good short­term response to stimulant medication.

Autism is the most severe of the pervasive developmental dis­orders (PDD). It is present from infancy and is characterized by a failure to develop social relationships, severe language delay, and compulsive and ritualistic activities. In about three­quarters of children with autism there is also mental retardation. Autism is relatively rare, but there are other more common, less severe, forms of PDD. Children with Asperger syndrome resemble chil­dren with autism in their social relationship difficulties and com­pulsive interests, but their language is much less impaired and they are of normal intelligence.

Schizophrenia is very uncommon in early adolescence, but when it does occur it is often severe and associated with much social impairment.

Overlap: there is a great deal of overlap between the various diagnostic categories. For example, around one­quarter of young people with conduct disorder will also develop a depressive

Main axis one diagnostic groups and their distinguishing features

Behavioural

disorders

Hyperkinetic

disorders

Emotional disorders Pervasive

developmental

disorder

Schizophrenia

diagnoses • oppositional–

defiant disorder

• Conduct disorder

• Hyperkinetic

disorder

• Hyperkinetic

conduct disorder

• mood disorders

• anxiety

• phobias

• obsessive–compulsive

disorder

• autism

• asperger

syndrome

• Schizophrenia

Sex m m+ m = F m++ m = F

age of onset any <5 years any <30 months >10 years

Family discord +++ ++ + − +/−

mental retardation + + − +++ +

Specific developmental

problems

++ +++ − +++ +

Impairment in adulthood ++ ++ + (++ if adolescent onset) +++ +++

Table 2

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disorder at some point. The two diagnostic systems take differ­ent approaches to comorbidity. • In ICD­10 it is assumed that a mixed clinical picture is more likely to be the result of a single disorder with different manifes­tations than of two or more disorders that happen to occur in the same individual at the same time. ICD­10 therefore has catego­ries for mixed disorders, such as mixed disorders of conduct and emotions and hyperkinetic conduct disorder. • DSM­IV, in contrast, usually allows the investigator to diag­nose several supposedly separate disorders, with the result that in surveys based on DSM­IV it is quite common to find individu­als with three or more diagnoses.

Specific disorders of psychological development

The second axis deals with an important group of problems, usu­ally known as developmental disorders (Table 3). They differ from psychiatric disorders in several respects: • the onset is invariably in infancy or childhood • their course is steady and does not involve the remissions and

relapses that characterize psychiatric disorders • there is specific delay in the development of functions that are

related to biological maturation of the brain.All disorders in this group are much more common in boys and there is often a family history of similar problems. From a psychiatric perspective, the two most important varieties are developmental disorders of speech and language, and specific reading retardation (also known as dyslexia).

Language disorder – there is much variation in the age at which children acquire language, and many slow speakers develop perfectly normally. Language delay outside the limits of two standard deviations that cannot be accounted for by mental retardation is usually regarded as abnormal. There is a very strong association between language disorders and psychiatric disorders. In most studies, more than 50% of children with a language disorder also have a psychiatric disorder, often behavi­oural problems.

Specific disorders of psychological development (ICD-10)

Specific developmental disorders of speech and language:

• Specific articulation disorder

• expressive language disorder

• receptive language disorder

• acquired aphasia with epilepsy

• other disorders of speech and language

Specific developmental disorders of scholastic skills:

• Specific reading disorder

• Specific spelling disorder

• Specific disorder of arithmetical skills

• mixed disorder of scholastic skills

Specific developmental disorder of motor function

Mixed specific developmental disorders

Table 3

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Specific reading disorder is characterized by impairment of reading skills that cannot be accounted for by mental retarda­tion, visual problems or inadequate educational opportunities. Children with specific reading problems often have a history of language delay. There is a strong association with psychiatric disorders. Around one­third of cases also have an emotional or conduct disorder.

Intellectual levelIn ICD­10 mental retardation (Table 4) is defined as a state of ‘arrested or incomplete development of the mind’. The degree of mental retardation is defined by the intelligence quotient (IQ), which should be estimated from standardized intelligence tests. The IQ level is, however, only a guide and should not be applied too rigidly. Children with mild mental retardation can often man­age in mainstream schools, though at the lower end of this range they may require additional support. Children with an IQ below 50 often require more intensive support or special schooling, and are likely to require supervision into adulthood.

Mental retardation is a strong risk factor for mental health problems. About one­third of children with mild mental retarda­tion have psychiatric disorders, and among children with moder­ate mental retardation the rate of disorder is about 50%. The mix of psychiatric disorders is similar to that seen in children with­out mental retardation, but autism and self­injury are particu­larly common among children with moderate and severe mental retardation.

Associated medical conditionsPhysical disorders not affecting the brain are associated with a moderate increase in the risk of psychopathology. Any medical disorder that affects the brain is associated with a 33% or more increased risk of psychiatric disorder.

Associated abnormal psychosocial situationsThere is a strong association between most child psychiatric dis­orders and abnormal psychosocial situations. In many instances it is unclear to what extent these connections reflect causal relationships, but since this axis is intended to cover situations that have contributed to the causes of the child’s problems, situations that are clearly a consequence of the child’s psycho­pathology are excluded. ICD­10 has a total of nine categories of

Intellectual level (ICD-10)

Mental

retardation

IQ Degree of impairment in adulthood

mild 50–69 most individuals fully independent; lower

end of this range may have problems

keeping a job and child-rearing

moderate 35–49 Completely independent living seldom

achieved

Severe 20–34 marked impairment

profound <20 require constant help and supervision

Table 4

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abnormal psychosocial situation. In routine clinical practice, the most commonly encountered situations are: • abnormal intrafamilial relationships • parental mental disorder • abnormal upbringing • acute life events.

Assessment of psychosocial disabilityThis final axis reflects the child’s occupational, psychological and social functioning at the time of the evaluation. Both epide­miological and clinical studies have consistently shown the pre­dictive value of psychosocial disability. This is also a very useful construct in planning mental health services for children. The ICD­10 assessment of psychosocial disability ranges from supe­rior functioning through moderate social disability (impairment

pSYCHIatrY 7:6 234

on one or two domains) to profound disability (unable to func­tion in any domain). ◆

FurTHEr rEADIng

american psychiatric association. diagnostic and statistical manual of

mental disorders, 4th edn. Washington, dC: apa, 1994.

taylor e, rutter m. Classification: conceptual issues and substantive

findings. In: rutter m, taylor e, eds. Child and adolescent psychiatry:

modern approaches, 4th edn. oxford: blackwell Science, 2002.

World Health organization. the ICd-10 classification of mental and

behavioural disorders: diagnostic criteria for research. Geneva:

WHo, 1993.

World Health organization. multiaxial classification of child and adolescent

psychiatric disorders. Cambridge: Cambridge University press, 1996.

© 2008 published by elsevier ltd.