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Autistic Spectrum Disorders
Autistic spectrum disorders comprise a group of conditions within the category of childhood-onset pervasive developmental disorders (ICD-10, DSM-IV).
Patricia Howlin
Autistic spectrum disorders comprise a group of conditions within the category of childhood-onset pervasive developmental disorders (ICD-10, DSM-IV). Autistic disorders are characterized by abnormalities in three domains:
- reciprocal social interactions
- communication
- restricted and repetitive patterns of behaviour or interests, with an onset in the first 3 years of life.
The term 'spectrum' is used to indicate the wide range of abilities and difficulties that may be found among individuals with these conditions. The two principal (and best defined) subgroups within the spectrum are autism and Asperger syndrome (Figures 1 and 2).
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FIGURE 1: ICD-10 criteria for autism
A. Abnormal or impaired development is evident before the age of 3 years in at least one of the following areas: 1. Receptive or expressive language as used in social communication B. A total of at least six symptoms from (1), (2), and (3) must be present, with at least two from (1) and at least one from each of (2) and (3): 1. Qualitative abnormalities in reciprocal social interaction
are manifest in at least two of the following areas: 2. Qualitative abnormalities in communication are manifest
in at least one of the following areas: |
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FIGURE 2: Criteria for Asperger syndrome
A. Qualitative abnormalities in reciprocal social interaction - criteria as for autism. However, lack of social reciprocity is more typically manifest by an eccentric and one-sided social approach to others, rather than social and emotional indifference B. Restricted, repetitive, and stereotyped patterns of
behaviour, interests, and activities - criteria as for autism C. The disturbance causes clinically significant impairment in social, occupational or other important areas of functioning D. There is no clinically significant general delay in language (i.e. single words by 2 years; communicative phrases by 3 years E. There is no significant delay in cognitive development, of age-appropriate self-help skills, adaptive behaviour, and curiosity about the environment F. Criteria are not met for another specific pervasive developmental disorder or schizophrenia |
Defining autism and Asperger syndrome
The condition of autism was first recognized in the 1940s by Leo Kanner in the USA. At much the same time, however, Hans Asperger, an Austrian psychiatrist, described a very similar group of children. The main difference was that Asperger's descriptions focused on relatively high-functioning individuals, whereas Kanner's case studies included children with marked delays in language and/or severe cognitive impairments. Although Kanner's work in this area was widely published, Asperger's accounts (probably because they were written in German shortly after the end of the Second World War) received little attention. Indeed Asperger syndrome was hardly heard of until the 1980s, when Lorna Wing highlighted the fact that autistic disorders could occur not only in individuals with marked linguistic and cognitive impairments, but also in those of high IQ, and with good expressive language skills (Wing, 1981).
The diagnostic criteria for Asperger syndrome and autism are very similar. The main differences are that in Asperger syndrome there is no clinically significant delay in language, and intellectual development is relatively unimpaired. Most recent research, however, indicates that there are no qualitative differences between individuals with a diagnosis of Asperger syndrome and those with autism whose cognitive skills are within the normal range.Incidence
Autistic spectrum disorder was once considered to be a very rare
condition, occurring in only around 3 to 4 per 10,000 children,
but more recent epidemiological studies suggest that the total
figure is much higher, with several studies indicating rates of
30-60 per 10,000 (Fombonne, 1999). Most evidence suggests that
the change represents a greater awareness of autistic spectrum
disorders among professionals, and improvements in diagnostic
practice more generally.
Sex ratio - like most other conditions involving language
impairments, autistic disorders are far more common in males than
females. The overall male:female ratio is estimated at around
4:1, although among high-functioning individuals, or those with
Asperger syndrome, the figure may be closer to 10:1. The male
predominance appears to be less marked among individuals with
severe intellectual disabilities (possibly around 2:1).
Diagnostic assessment
Diagnosis in autism relies on the identification of a constellation
of specific symptoms. Deficits in these areas must also be distinguished
from deficits that may be attributable to low IQ, sensory impairments
(e.g. deafness) or other developmental or psychiatric disorders.
Reliable diagnosis can be achieved only on the basis of a detailed
developmental history, focusing on social development, the development
of communication skills, and patterns of repetitive or stereotyped
behaviours and interests.
Diagnostic instruments: a number of standardized diagnostic instruments have been developed to enhance diagnostic accuracy (Figure 3). The Autism Diagnostic Interview - Revised (ADI-R; Lord et al., 1994) is among the most widely used. The Diagnostic Interview for Social and Communication Disorders (DISCO; Wing et al., 2002) also provides a structured framework for the assessment of developmental and behavioural functioning. Parental information may be supplemented by standardized observational measures such as the Autism Diagnostic Observational Schedule (ADOS; Lord et al., 1999). Various checklists are also available, including:
- Childhood Autism Rating Scale (Schopler et al., 1986)
- Autism Behavior Checklist (Krug et al., 1980)
- Autism Screening Questionnaire, which is derived from the ADI-R (Berument et al., 1999).
| FIGURE 3: Diagnostic instruments for
autism and autism spectrum disorder
Although many different checklists and screening instruments for the identification of possible autistic spectrum disorders exist these cannot be use for clinical diagnostic purposes. A conclusive diagnosis can be reached only on the basis of a detailed developmental history. Of the very few instruments available that can be used to provide this information, the best validated are:
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Cognitive assessments: the diagnostic process should also incorporate assessments of cognitive and verbal ability. Again, a variety of different instruments is available. Psychometric tests suitable for use with children with autism include the Wechsler Scales, the Mullen Scales, the Merrill Palmer Scales and the Bayley Scales, and there is a wide choice of language tests. The Vineland Adaptive Behavior Scales (Sparrow et al., 1984) can be particularly helpful for very young or severely intellectually impaired individuals, as they assess functioning in several domains across a wide age range and are based on parental information. Generally, however, a single test will not be sufficient and a combination of different methods - observational, parent-based and standardized assessments - is needed in order to obtain a valid picture of the child's functioning across a range of different areas.
Physical examination: a comprehensive physical examination
is required in order to identify any additional disorders (e.g.
tuberous sclerosis or fragile-X (see also Sabaratnam 2003; pp.
29-33)) or specific neurological impairments. It is important,
too, to assess vision, hearing and motor coordination, as impairments
in these areas may affect children's general functioning. The
presence of common comorbid conditions, such as attention deficit
disorders, should also be investigated.
Epilepsy (see also Bernal 2003; pp.69-73) occurs in around 25%
of cases, but often does not develop until the early teens, and
it is important to be alert to the possibility of seizures if
sudden, unexplained changes in behaviour occur. However, EEG abnormalities
in autism are common, and, in the absence of other symptoms, are
not in themselves an indication for anti-epileptic medication.
Routine neuroimaging is unlikely to be justified, unless there
are marked changes in the child's behaviour.
Differential diagnosis
A number of other conditions affecting early development may be
confused with autistic spectrum disorders, including developmental
language disorders, severe psychosocial deprivation, profound
intellectual impairment, selective mutism, early childhood schizophrenia,
Rett syndrome, childhood disintegrative disorders and Landau-Klefner
syndrome. However, the onset, course, response to intervention
and family background in these disorders are generally different
from those found in autism (see Lord and Bailey, 2002, for review).
In most cases, a detailed developmental and family history, together
with careful physical, psychometric and linguistic assessments
will avoid diagnostic confusion.
Causes
Theories about the causes of autism have changed markedly over
the years. When Kanner first described the condition, he, and
many other professionals, believed that inadequate parenting was
the primary culprit. Recent increases in the numbers of children
diagnosed with autism have also led to a search for possible environmental
causes. However, there is no evidence that environmental factors
such as vaccinations (notably the MMR vaccine), pollutants, dietary
additives, and so on, are in any way responsible. Instead, it
has become increasingly apparent that autism is largely a genetic
disorder (Lord and Bailey, 2002). It was recognized as early as
the 1970s that families with one autistic child had a greatly
increased risk of having other children with autism or related
disorders. Subsequent twin studies indicated very high concordance
rates among monozygotic twins, and recent large-scale family studies
have identified higher rates of social and communication difficulties
and increased rates of circumscribed interests or obsessional
and repetitive behaviours among relatives. There is also an increased
risk of depressive disorders among relatives.
The pattern of inheritance in autism is unclear, but between two
and 10 susceptibility genes are probably implicated, with three
or four interacting loci being the most likely model. Research
is now concentrating on the identification of susceptibility genes,
with the focus on specific chromosomal regions, particularly 7q
and 15q. Other regions of interest include 2q, 13q, 16p and 19p.
Cognitive deficits
Most children with autistic spectrum disorders, apart from those
with Asperger syndrome, also have intellectual impairments. Around
half of all individuals with autism have an IQ below 50. Only
around 20% have an IQ in the normal range (i.e. >70). Verbal
skills are generally relatively more severely impaired than non-verbal
skills.
Different psychological hypotheses have been proposed to identify
and explain the specific cognitive deficits underlying autistic
spectrum disorders. Among the most influential of these are theories
focusing on:
- the failure to understand other people's mental states
- deficits in understanding emotions or facial expression
- impairments in executive function
- a lack of central coherence.
Attentional deficits and impairments in voice recognition and
visual integration have also been proposed as possible contributory
factors. Findings from neurobiological studies are generally inconsistent,
or contradictory. Various different abnormalities have been implicated
(e.g. decreased Purkinje cell density in the cerebellum, significantly
increased brain size, abnormal amygdala function and abnormalities
in the serotonergic system). However, much of the work in this
field has been conducted on very small groups of subjects, diagnostic
criteria are often unclear and the impact of variables such as
age, intellectual impairment or language level has rarely been
taken into account.
Data from both post-mortem and neuroimaging studies suggest that
autistic spectrum disorders affect the development and function
of the cerebral cortex and subcortical structures, but there is
considerable individual variation, and even when deficits have
been found, it is unclear whether these are primary abnormalities,
or whether the deficits are attributable to connectivity within
and between different structures (Lord and Bailey, 2002).
Course of autism
Outcome in autism is highly dependent on individuals' general
intellectual level, and also on whether or not they acquire useful
language. Few children with an IQ below 70 achieve independence
as adults, and many of those with an IQ in the normal range still
require support in terms of living and work throughout their lives
(see figure below). The early symptoms of
autism are generally first recognized by parents by the second
year of life, and often long before this. Nevertheless, many children
do not receive a formal diagnosis until they are 4 or 5 years
of age or even later. Problems of social relationships, reciprocal
communication, or lack of imaginative play are generally the first
symptoms of which parents are aware. Ritualistic and stereotyped
behaviours may not become apparent until children are older -
around 3-4 years. The preschool period (4-5 years) is often the
time when autistic symptomatology is most marked. A quarter to
one-third of parents report that, typically around 18-24 months
and following an apparently normal period of development, their
children lose speech, and sometimes social skills too.
On the whole, most children show improvements in many aspects
of their development as they grow older. Some individuals do show
an increase in behavioural disturbance in adolescence but this
is by no means inevitable, and many actually show marked improvements
in their mid to late teens.
The importance of early diagnosis: although diagnosis
as early in childhood as possible is clearly desirable for many
reasons, the presence of autistic features may sometimes go unrecognized
if children do not show a 'classic' picture of autism. There is
a particular risk of failing to diagnose autistic spectrum disorders
in individuals with severe intellectual disabilities, or in those
who have additional impairments (deafness, blindness, Down's syndrome,
cerebral palsy, etc). Diagnosis may also be significantly delayed
in children who are higher functioning, particularly those who
have Asperger syndrome.
Even if autism has not been diagnosed in childhood, the presence
of social and language impairments that are out of keeping with
the individual's overall level of functioning, and an over-reliance
on routines or stereotyped patterns of behaviour and/or interests,
should alert professionals to the possibility of an autistic disorder.
Several of the diagnostic instruments initially designed for children
(e.g. ADI and ADOS) can be used reliably with adults, and although
there may sometimes be problems in finding an appropriate informant
if parents are very elderly or no longer alive, a satisfactory
developmental history can frequently be obtained from siblings
or other relatives. Late diagnosis is better than no diagnosis,
as it is only when an individual's needs and difficulties are
correctly identified that appropriate intervention is likely to
result.
Interventions for autism
Many different treatments have been suggested as being effective
for individuals with autism, some of these even claiming to bring
about cures or recovery from the condition. On the whole, however,
these claims are rarely supported by evidence, and many treatments
have never been adequately evaluated. Others - such as facilitated
communication, holding therapy, auditory integration therapy or
secretin injections - have been found to be no more effective
than placebo, despite initial claims of almost 'miraculous' results.
On the whole, structured educational programmes, combining behaviourally
based strategies and developmental approaches, and utilizing visual
schedules and cues rather than verbal instruction, tend to have
more positive outcomes. The involvement of families in treatment,
and a focus on strategies that build on the child's strengths
rather than areas of specific weakness, also appear to be important.
It is generally agreed that behavioural/educational/developmental
programmes are a good option for children with autism, but as
yet there is no evidence in support of any one particular programme,
particular degree of structure or any specific degree of intensity
(Howlin, 2001).
Medication: the use of medication for individuals with autism varies widely; rates are particularly high in the USA, but much less in other countries, such as the UK. While appropriate medication is clearly important for conditions that may be associated with autism, such as epilepsy or high anxiety, there are no medications that are effective for autism per se, and hence the routine use of medication, particularly for very young children should be discouraged unless there is a specific reason.
Autism in adulthood
Much of the research into the diagnosis and treatment of autistic
spectrum disorders has focused on children and, despite the fact
that autism is a life-long condition, the needs of adolescents
and adults often seem to be neglected. For example, although autism
is known to be very common among adults with severe intellectual
impairments, staff in residential care units may be unaware of
the presence of autistic features or of the importance of differential
diagnosis for developing appropriate management and support strategies.
However, the poor social and communication skills of people with
autism (which are out of keeping even with their level of intellectual
impairment) and their need for ritual and routine, can make it
very difficult for them to cope with the demands of group living,
and severe emotional and behavioural disturbance is often the
result (Joyce 2003; pp.17-20). Staff recognition of their dependence
on predictability and structure, of the importance of rituals
or routines, and of their need for consistency (both of environment
and personnel), together with acceptance of a general disinclination
to take part in 'normal' social activities, can greatly help to
reduce stress, anxiety and disruption. A focus on developing more
effective communication by whatever means are appropriate (signs,
pictures, objects or symbols) can also have a major impact on
other aspects of behaviour. Even among more able adults, many
individuals remain heavily dependent on others for support, and,
without help, only a minority seem to cope with living fully independently,
finding appropriate work, making close relationships or developing
long-term sexual relationships/marriage (Howlin et al., in press).
Although access to appropriate help from an early age can be of
considerable benefit, this should not detract from resources for
older children and adults. As adolescence can be a time of positive
change, there is a need for more widespread and effective intervention
programmes at this stage. Specific interventions in adulthood,
such as the provision of specially designed supported living and
employment schemes, can have a major impact on later outcome.
Conclusion
The understanding of autistic spectrum disorders has improved
significantly since autism was first described in the 1940s. It
is now accepted that autistic disorders are far more common than
was once thought, that they can affect individuals of all cognitive
levels, and that they are, in the majority of cases, genetically
determined. However, much research is still required in order
to develop optimal intervention strategies, not just in childhood,
but across the lifespan. Far more is still to be learned, too,
about the genetic mechanisms involved, and the ways in which these
affect brain development and brain function.
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PRACTICE POINTS
Any child who shows the following abnormalities of development should be considered as being at risk of having an autistic spectrum disorder:
An appropriate screening instrument (e.g. the Checklist for Autism in Toddlers, or CHAT) can be used to further explore the possibility of autism. Clinical diagnosis should be made by a multidisciplinary team and at all times parents should be fully involved in the process No cures for autism exist, but much can be done to improve outcome. Diagnosis must be followed by practical support for families and access to appropriate educational provision. Later, adequate educational, social, residential and employment support services will be needed to ensure the successful transition into adult life |
REFERENCES
Bernal J. Epilepsy in People with Learning Disabilities. Psychiatry 2003; 2:9: 69-73
Berument S K, Rutter M, Lord C, Pickles A, Bailey A. Autism Screening Questionnaire: diagnostic validity. Br J Psychiatry 1999; 175: 444-51.
Fombonne E. The epidemiology of autism: a review. Psychol Med 1999; 29: 769-86.
Howlin P. From Aveyron to Swimming with Dolphins. Association of Child Psychology and Psychiatry Occasional Papers 17. London: ACPP, 2001.
Joyce T. Functional Analysis and Challenging Behaviour. Psychiatry 2003; 2:8: 17-20.
Krug D A, Arick J, Almond P. Behavior checklist for identifying severely handicapped individuals with high levels of autistic behaviour. J Child Psychol Psychiatry 1980; 21: 221-9.
Lord C, Bailey A. Autism spectrum disorders. In: Rutter M, Taylor E, eds. Child and Adolescent Psychiatry. 4th edition. Oxford: Blackwell, 2002.
Lord C, Rutter M, DiLavore P, Risi S. Autism Diagnostic Observation Schedule (ADOS). Los Angeles: Western Psychological Services, 1999.
Lord C, Rutter M, Le Couteur A. Autism Diagnostic Interview-Revised: a revised version of a diagnostic interview for carers of individuals with possible pervasive developmental disorders. J Autism Dev Disord 1994; 24: 659-85.
Sabaratnam M. Fragile-X Syndrome. Psychiatry 2003; 2:8: 29-33.
Schopler E, Reichler R J, Renner B R. The Childhood Autism Rating Scale (CARS) for Diagnostic Screening and Classification of Autism. New York: Irvington, 1986.
Sparrow S S, Balla D, Cicchetti D V. Vineland Adaptive Behavior Scales. Circle Pines, MN: American Guidance Service, 1984.
Wing L. Asperger's syndrome: A clinical account. Psychol Med 1981; 11: 115-29.
Wing L, Leekham S, Gould J. The Diagnostic Interview for Social and Communication Disorders: background, inter-rater reliability and clinical use. J Child Psychol Psychiatry 2002; 43: 307-25.
| First published in Psychiatry; Volume 2:8 in August 2003 and reprinted with the kind permission of the Medicine Publishing Company. |
Figure 4 is taken from Cooke LB. Aetiology of Learning Disability. Psychiatry 2003, 2:8, p.5
