Autism Spectrum Disorder (ASD)

Overview

What is autism spectrum disorder?

Autism Spectrum Disorder (ASD) is a neurodevelopmental disorder that affects an individual’s social communication and interaction, as well as their patterns of behaviour, interests, and activities. The severity of symptoms can range from mild to severe, which is why it is considered a spectrum disorder.

ASD can affect anyone, regardless of age, gender, or ethnicity and it is estimated that 1 in 160 children worldwide has ASD, with a higher prevalence in boys than girls.It can also present differently in each individual, making it difficult to diagnose. Some individuals with ASD may have difficulty with eye contact, social cues, and understanding emotions, while others may have repetitive behaviours or routines, sensory sensitivities, and difficulty with changes in routine.

The essential features of autism spectrum disorder are persistent impairment in reciprocal social communication and social interaction, and restricted, repetitive patterns of behaviour, interests, or activities. These symptoms are present from early childhood and limit or impair everyday functioning.

The stage at which functional impairment becomes obvious will vary according to the characteristics of the individual and their environment. Core diagnostic features are evident in the developmental period, but intervention, compensation, and current supports may mask difficulties in at least some contexts.

Manifestations of the disorder also vary greatly depending on the severity of the autistic condition, developmental level, and chronological age; hence, the term spectrum. Autism spectrum disorder encompasses disorders previously referred to as early infantile autism, childhood autism, Kanner’s autism, high-functioning autism, atypical autism, pervasive developmental disorder not otherwise specified, childhood disintegrative disorder, and Asperger’s disorder.

Symptoms and causes

Symptoms of autism

Social communication

Persistent deficits in social communication and social interaction across multiple contexts, as manifested by the following, currently or by history (examples are illustrative, not exhaustive; see text):

1. Deficits in social-emotional reciprocity, ranging, for example, from abnormal social approach and failure of normal back-and-forth conversation; to reduced sharing of interests, emotions, or affect; to failure to initiate or respond to social interactions.
2. Deficits in nonverbal communicative behaviours used for social interaction, ranging, for example, from poorly integrated verbal and nonverbal communication; to abnormalities in eye contact and body language or deficits in understanding and use of gestures; to a total lack of facial expressions and nonverbal communication.
3. Deficits in developing, maintaining, and understanding relationships, ranging, for example, from difficulties adjusting behaviour to suit various social contexts; to difficulties in sharing imaginative play or in making friends; to absence of interest in peers.

Restricted, repetitive behaviours

Restricted, repetitive patterns of behaviour, interests, or activities, as manifested by at least two of the following, currently or by history (examples are illustrative, not exhaustive; see text):

1. Stereotyped or repetitive motor movements, use of objects, or speech (e.g., simple motor stereotypies, lining up toys or flipping objects, echolalia, idiosyncratic phrases).
2. Insistence on sameness, inflexible adherence to routines, or ritualised patterns of verbal or nonverbal behaviour (e.g., extreme distress at small changes, difficulties with transitions, rigid thinking patterns, greeting rituals, need to take the same route or eat the same food every day).
3. Highly restricted, fixated interests that are abnormal in intensity or focus (e.g., strong attachment to or preoccupation with unusual objects, excessively circumscribed or perseverative interests).
4. Hyper- or hypo-reactivity to sensory input or unusual interest in sensory aspects of the environment (e.g., apparent indifference to pain/temperature, adverse response to specific sounds or textures, excessive smelling or touching of objects, visual fascination with lights or movement).

In addition

• Symptoms must be present in the early developmental period (but may not become fully manifest until social demands exceed limited capacities, or may be masked by learned strategies in later life).
• Symptoms cause clinically significant impairment in social, occupational, or other important areas of current functioning.
• These disturbances are not better explained by intellectual disability (intellectual developmental disorder) or global developmental delay. Intellectual disability and autism spectrum disorder frequently co-occur; to make comorbid diagnoses of autism spectrum disorder and intellectual disability, social communication should be below that expected for general developmental level.

Many individuals with autism spectrum disorder also have intellectual impairment and/or language impairment (e.g., slow to talk, language comprehension behind production). Even those with average or high intelligence have an uneven profile of abilities and the gap between intellectual and adaptive functional skills is often large.

Motor deficits are often present, including odd gait, clumsiness, and other abnormal motor signs (e.g., walking on tiptoes).

Self-injury (e.g., head banging, biting the wrist) may occur, and disruptive/challenging behaviours are more common in children and adolescents with autism spectrum disorder than other disorders, including intellectual disability.

Adolescents and adults with autism spectrum disorder are prone to anxiety and depression.

Some individuals develop catatonic-like motor behaviour (slowing and “freezing” mid-action), but these are typically not of the magnitude of a catatonic episode. However, it is possible for individuals with autism spectrum disorder to experience a marked deterioration in motor symptoms and display a full catatonic episode with symptoms such as mutism, posturing, grimacing and waxy flexibility. The risk period for comorbid catatonia appears to be greatest in the adolescent years.

Severity levels

The severity specifiers below may be used to describe the current symptomatology (which might fall below level 1), with the recognition that severity may vary by context and fluctuate over time. The severity of social communication difficulties and restricted, repetitive behaviours should be separately rated.

Level 3 – Requiring very substantial support

• Social communication: Severe deficits in verbal and nonverbal social communication skills cause severe impairments in functioning, very limited initiation of social interactions, and minimal response to social overtures from others. For example, a person with few words of intelligible speech who rarely initiates interaction and, when he or she does, makes unusual approaches to meet needs only and responds to only very direct social approaches.
• Restricted, repetitive behaviours: Inflexibility of behaviour, extreme difficulty coping with change, or other restricted/repetitive behaviours markedly interfere with functioning in all spheres. Great distress/difficulty changing focus or action.

Level 2 – Requiring substantial support

• Social communication: Marked deficits in verbal and nonverbal social communication skills; social impairments apparent even with supports in place; limited initiation of social interactions; and reduced or abnormal responses to social overtures from others. For example, a person who speaks simple sentences, whose interaction is limited to narrow special interests, and who has markedly odd nonverbal communication.
• Restricted, repetitive behaviours: Inflexibility of behaviour, difficulty coping with change, or other restricted/repetitive behaviours appear frequently enough to be obvious to the casual observer and interfere with functioning in a variety of contexts. Distress and/or difficulty changing focus or action.

Level 1 – Requiring support

• Social communication: Without supports in place, deficits in social communication cause noticeable impairments. Difficulty initiating social interactions, and clear examples of atypical or unsuccessful responses to social overtures of others. May appear to have decreased interest in social interactions. For example, a person who is able to speak in full sentences and engages in communication but whose to-and-fro conversation with others fails, and whose attempts to make friends are odd and typically unsuccessful.
• Restricted, repetitive behaviours: Inflexibility of behaviour causes significant interference with functioning in one or more contexts. Difficulty switching between activities. Problems of organisation and planning hamper independence.

Causes of autism

The exact causes of ASD are still unknown, but it is believed to be a combination of genetic and environmental factors. Research has shown that certain genetic mutations and environmental factors such as prenatal exposure to toxins may increase the risk of developing ASD.

• Environmental: A variety of nonspecific risk factors, such as advanced parental age, low birth weight, or fetal exposure to valproate, may contribute to risk of autism spectrum disorder.
• Genetic and physiological: Heritability estimates for autism spectrum disorder have ranged from 37% to higher than 90%, based on twin concordance rates. Currently, as many as 15% of cases of autism spectrum disorder appear to be associated with a known genetic mutation, with different de novo copy number variants or de novo mutations in specific genes associated with the disorder in different families. However, even when an autism spectrum disorder is associated with a known genetic mutation, it does not appear to be fully penetrant. Risk for the remainder of cases appears to be polygenic, with perhaps hundreds of genetic loci making relatively small contributions.

It is important to note that not all individuals with ASD have identifiable genetic or environmental risk factors.

Diagnosis and treatment

How is autism diagnosed?

Autism is typically diagnosed by mental health providers or primary care providers. Healthcare providers use the guidelines in the American Psychiatric Association’s Diagnostic and Statistical Manual, Fifth edition (DSM-5), to help diagnose autism spectrum disorder. This diagnostic standard helps ensure that people are appropriately diagnosed and treated for autism. Using the same standard across communities can also help determine how many children have autism, and how public health is impacted by this condition.

A psychiatric evaluation will normally include a description of symptoms, completion of scales and questionnaires, gaining an understanding of psychiatric and medical history, family history, and information regarding education, environment, and upbringing. It may also include a referral for medical evaluation to rule out other medical conditions.

Some individuals come for first diagnosis in adulthood, perhaps prompted by the diagnosis of autism in a child in the family or a breakdown of relations at work or home. Obtaining detailed developmental history in such cases may be difficult, and it is important to consider self-reported difficulties. Where clinical observation suggests criteria are currently met, autism spectrum disorder may be diagnosed, provided there is no evidence of good social and communication skills in childhood.

For example, the report (by parents or another relative) that the individual had ordinary and sustained reciprocal friendships and good nonverbal communication skills throughout childhood would rule out a diagnosis of autism spectrum disorder; however, the absence of developmental information in itself should not do so.

Only trained healthcare providers can diagnose or treat autism.

Differential diagnosis for autism

Differential diagnosis can include:

• Attention-deficit/hyperactivity disorder (ADHD): Abnormalities of attention (overly focused or easily distracted) are common in individuals with autism spectrum disorder, as is hyperactivity. A diagnosis of attention-deficit/hyperactivity disorder (ADHD) should be considered when attentional difficulties or hyperactivity exceeds that typically seen in individuals of comparable mental age.
• Intellectual disability (intellectual developmental disorder) without autism spectrum disorder: Intellectual disability without autism spectrum disorder may be difficult to differentiate from autism spectrum disorder in very young children. Individuals with intellectual disability who have not developed language or symbolic skills also present a challenge for differential diagnosis, since repetitive behaviour often occurs in such individuals as well. A diagnosis of autism spectrum disorder in an individual with intellectual disability is appropriate when social communication and interaction are significantly impaired relative to the developmental level of the individual’s nonverbal skills (e.g., fine motor skills, nonverbal problem solving). In contrast, intellectual disability is the appropriate diagnosis when there is no apparent discrepancy between the level of social-communicative skills and other intellectual skills.
• Language disorders and social (pragmatic) communication disorder: In some forms of language disorder, there may be problems of communication and some secondary social difficulties. However, specific language disorder is not usually associated with abnormal nonverbal communication, nor with the presence of restricted, repetitive patterns of behaviour, interests, or activities. When an individual shows impairment in social communication and social interactions but does not show restricted and repetitive behaviour or interests, criteria for social (pragmatic) communication disorder, instead of autism spectrum disorder, may be met. The diagnosis of autism spectrum disorder supersedes that of social (pragmatic) communication disorder whenever the criteria for autism spectrum disorder are met, and care should be taken to enquire carefully regarding past or current restricted/repetitive behaviour.
• Rett syndrome: Disruption of social interaction may be observed during the regressive phase of Rett syndrome (typically between 1–4 years of age); thus, a substantial proportion of affected young girls may have a presentation that meets diagnostic criteria for autism spectrum disorder. However, after this period, most individuals with Rett syndrome improve their social communication skills, and autistic features are no longer a major area of concern. Consequently, autism spectrum disorder should be considered only when all diagnostic criteria are met.
• Schizophrenia: Schizophrenia with childhood onset usually develops after a period of normal, or near normal, development. A prodromal state has been described in which social impairment and atypical interests and beliefs occur, which could be confused with the social deficits seen in autism spectrum disorder. Hallucinations and delusions, which are defining features of schizophrenia, are not features of autism spectrum disorder. However, clinicians must take into account the potential for individuals with autism spectrum disorder to be concrete in their interpretation of questions regarding the key features of schizophrenia (e.g., “Do you hear voices when no one is there?” ”Yes [on the radio]”).
• Selective mutism: In selective mutism, early development is not typically disturbed. The affected child usually exhibits appropriate communication skills in certain contexts and settings. Even in settings where the child is mute, social reciprocity is not impaired, nor are restricted or repetitive patterns of behaviour present.
• Stereotypic movement disorder: Motor stereotypies are among the diagnostic characteristics of autism spectrum disorder, so an additional diagnosis of stereotypic movement disorder is not given when such repetitive behaviours are better explained by the presence of autism spectrum disorder. However, when stereotypies cause self-injury and become a focus of treatment, both diagnoses may be appropriate.

Treatment for autism

Therapy

There are various treatments available in Australia for individuals diagnosed with ASD. Behavioural therapy is one of the most commonly used interventions, which includes Applied Behavioural Analysis (ABA), Early Start Denver Model (ESDM), and Positive Behavior Support (PBS).

• Applied behavioural analysis: ABA is a structured therapy that focuses on using positive reinforcement to encourage desired behaviours.
• Early start Denver model: ESDM is an early intervention program for children under five years old that incorporates play-based activities to promote social interaction and language development.
• Positive behavior support: PBS is a treatment that focuses on addressing problematic behaviours by analysing the function of the behavior and developing a plan to address it.

Medication

Medication is typically not used as a first-line treatment, however, medications such as antipsychotics, antidepressants, and stimulants can be used to treat comorbid conditions such as anxiety, depression, or ADHD.

Comorbidity

• Intellectual impairment and structural language disorder: Autism spectrum disorder is frequently associated with intellectual impairment and structural language disorder (i.e., an inability to comprehend and construct sentences with proper grammar), which should be noted under the relevant specifiers when applicable.
• Other mental disorders: Many individuals with autism spectrum disorder have psychiatric symptoms that do not form part of the diagnostic criteria for the disorder (about 70% of individuals with autism spectrum disorder may have one comorbid mental disorder, and 40% may have two or more comorbid mental disorders). When criteria for both ADHD and autism spectrum disorder are met, both diagnoses should be given. This same principle applies to concurrent diagnoses of autism spectrum disorder and developmental coordination disorder, anxiety disorders, depressive disorders, and other comorbid diagnoses. Among individuals who are nonverbal or have language deficits, observable signs such as changes in sleep or eating and increases in challenging behaviour should trigger an evaluation for anxiety or depression.
• Specific learning difficulties: Specific learning difficulties (literacy and numeracy) are common, as is developmental coordination disorder.
• Other medical conditions: Medical conditions such as epilepsy, sleep problems, and constipation are commonly associated with autism spectrum disorder.
• Avoidant-restrictive food intake disorder: Avoidant-restrictive food intake disorder is a fairly frequent presenting feature of autism spectrum disorder, and extreme and narrow food preferences may persist.

Outlook and prognosis

Development and course

Symptoms are typically recognised during the second year of life (12–24 months of age) but may be seen earlier than 12 months if developmental delays are severe, or noted later than 24 months if symptoms are more subtle. The pattern of onset description might include information about early developmental delays or any losses of social or language skills. In cases where skills have been lost, parents or caregivers may give a history of a gradual or relatively rapid deterioration in social behaviours or language skills. Typically, this would occur between 12 and 24 months of age and is distinguished from the rare instances of developmental regression occurring after at least 2 years of normal development (previously described as childhood disintegrative disorder).

The behavioural features of autism spectrum disorder first become evident in early childhood, with some cases presenting a lack of interest in social interaction in the first year of life.

Some children with autism spectrum disorder experience developmental plateaus or regression, with a gradual or relatively rapid deterioration in social behaviours or use of language, often during the first 2 years of life. Such losses are rare in other disorders and may be a useful “red flag” for autism spectrum disorder. Much more unusual and warranting more extensive medical investigation are losses of skills beyond social communication (e.g., loss of self-care, toileting, motor skills) or those occurring after the second birthday.

The first symptoms of autism spectrum disorder frequently involve delayed language development, often accompanied by a lack of social interest or unusual social interactions (e.g., pulling individuals by the hand without any attempt to look at them), odd play patterns (e.g., carrying toys around but never playing with them), and unusual communication patterns (e.g., knowing the alphabet but not responding to own name). Deafness may be suspected but is typically ruled out.

During the second year, odd and repetitive behaviours and the absence of typical play become more apparent. Since many typically developing young children have strong preferences and enjoy repetition (e.g., eating the same foods, watching the same video multiple times), distinguishing restricted and repetitive behaviours that are diagnostic of autism spectrum disorder can be difficult in preschoolers. The clinical distinction is based on the type, frequency, and intensity of the behaviour (e.g., a child who daily lines up objects for hours and is very distressed if any item is moved).

Functional consequences of autism

Autism spectrum disorder is not a degenerative disorder, and it is typical for learning and compensation to continue throughout life. Symptoms are often most marked in early childhood and early school years, with developmental gains typical in later childhood in at least some areas (e.g., increased interest in social interaction).

A small proportion of individuals deteriorate behaviourally during adolescence, whereas most others improve. Only a minority of individuals with autism spectrum disorder live and work independently in adulthood; those who do tend to have superior language and intellectual abilities and are able to find a niche that matches their special interests and skills. In general, individuals with lower levels of impairment may be better able to function independently. However, even these individuals may remain socially naive and vulnerable, have difficulties organising practical demands without aid, and are prone to anxiety and depression. Many adults report using compensation strategies and coping mechanisms to mask their difficulties in public but suffer from the stress and effort of maintaining a socially acceptable facade. Scarcely anything is known about old age in autism spectrum disorder.

Manifestations of the social and communication impairments and restricted/repetitive behaviours that define autism spectrum disorder are clear in the developmental period. In later life, intervention or compensation, as well as current supports, may mask these difficulties in at least some contexts. However, symptoms remain sufficient to cause current impairment in social, occupational, or other important areas of functioning.

Prognosis

The prognosis for individuals with ASD varies depending on the severity of symptoms and the effectiveness of interventions. Early intervention is key to improving outcomes, and individuals who receive early and intensive behavioural therapy are more likely to show improvement in social skills, communication, and adaptive functioning. However, some individuals may require ongoing support throughout their lives.

The best established prognostic factors for individual outcome within autism spectrum disorder are presence or absence of associated intellectual disability and language impairment (e.g., functional language by age 5 years is a good prognostic sign) and additional mental health problems. Epilepsy, as a comorbid diagnosis, is associated with greater intellectual disability and lower verbal ability.