Autism spectrum disorder is characterized by deficits in social communication and restricted, repetitive and/or sensory behaviours or interests. The severity levels should be specified.

In the 1970s, only 1.5% of the children with ASD achieved normal functioning. About 35% showed good adjustment but required some degree of supervision. The majority (i.e. 60%) remained severely handicapped. About 50% remained non-verbal throughout their lives. Currently, this is less than 10%. However, ASD does not need to be a life-long disabling condition. About 25% of the children can lose the diagnosis after treatment and most children can achieve positive outcomes with treatment. Children who lose the diagnosis will become similar to typically developing children.

There are several criteria for when an intervention is successful:

• Reduction in symptoms (e.g. less repetitive behaviours).
• Developmental improvements (e.g. learning to speak).
• Reduction in problem behaviours (e.g. fewer temper tantrums).
• Better coping with daily expectations (e.g. attending regular education).

However, when an intervention is truly successful depends on the goals of the parents and the child. The intervention should aim to improve on these goals and should thus be matched to their goals.

Lovaas’ discrete trial training (DTT) demonstrated that behaviour modification treatment could lead to positive outcomes for children with ASD. This training makes use of operant techniques and breaks skills into small component and teaches the child one component at a time. According to Lovaas, children with ASD are unsuccessful in learning skills from the natural environment and the environment should thus include potent reinforcers and should be simplified. This means that every small step is rewarded. Though the training seems effective, there is a lack of generalization of learned skills (1), it leads to avoidance behaviour (2), there is a lack of spontaneity (3) and there is an overdependence on prompts (4). This could be because the treatment is very therapist-directed.

Applied behavioural analysis refers to the process of systematically applying interventions based upon learning theory principles to improve socially significant behaviours to a meaningful degree. It aims to change behaviour by investigating what is reinforcing the behaviour and it is the core of all interventions for ASD.

The core of all interventions for ASD is applied behavioural analysis. This refers to systematically applying interventions based on learning theory principles to improve socially significant behaviours to a meaningful degree. This approach aims to change behaviour by investigating what is reinforcing the behaviour:

• Applied (i.e. improvement of socially significant behaviour).
• Behaviour (i.e. observable and measurable).
• Analysis (i.e. checking whether interventions cause behavioural change).

ABA can focus on social skills (1), communication (2), play (3), behaviour (4), adaptive skills (5), motor skills (6) and cognitive skills (7), meaning that the focus of ABA in children with ASD can be very heterogeneous. These skills often develop naturally in typically developing children.

ABA attempts to understand and alter the environment to change behaviour using the ABC contingency:

• Antecedent (i.e. what happens before behaviour).
• Behaviour (i.e. the actual behaviour).
• Consequence (i.e. what happens after behaviour).

The aim is to increase desirable and decrease undesirable behaviours using this contingency. Reinforcement increases the future likelihood of behaviour. This can be positive (i.e. adding an environmental stimulus) or negative (i.e. removing an environmental stimulus). Punishment decreases the future likelihood of behaviour. This can also be positive or negative. Extinction refers to removing reinforcement of undesirable behaviour.

Treatments for children with ASD should have several characteristics:

• It should focus on improving joint attention (i.e. to share information).
• It should focus on improving imitation (i.e. to improve ToM).
• It should view the child as an active rather than passive agent.
• It should focus on social relationships, including with the therapist.
• It should include affective engagement.

Naturalistic developmental behavioural interventions (NDBIs) refer to empirically supported autism interventions that represent the merging of applied behavioural and developmental sciences. These intervention employ a naturalistic and interactive social context and involve child-directed teaching strategies). It has several characteristics (i.e. common elements):

• It uses ABA as a core, manualized, measurement of progress.
• It makes use of fidelity of implementation criteria.
• It has individualized treatment goals and ongoing measurement of progress.
• It focuses on generalization of acquired skills (i.e. teaching in the natural environment).
• It makes use of emotionally meaningful interactions.
• It uses natural contingencies (i.e. no ‘artificial’ rewards).
• It uses environmental arrangement.
• It uses scaffolding (i.e. prompting).
• It makes use of modelling by the therapist.
• It aims to have child-initiated teaching episodes.
• It aims to broaden the attentional focus of the child.
• It makes use of environmental arrangement.
• It makes use of reciprocal imitation.
• It makes use of balanced turns within object or social play routines (i.e. turn taking).

NDBIs have several benefits:

• It leads to a reduced dependence on prompts.
• It leads to a more natural-sounding language.
• It makes learning language meaning more efficient.
• It leads to habituation to everyday distractions present in the real-world.

NDBIs attempt to provide the child with an infrastructure to support efficient and effective learning. These interventions aim to establish adult-child engagement activities that transform into motivating play routines or familiar daily life routines as learning is improved when it is embedded in activities that contain emotionally meaningful interactions.

The pivotal response treatment (PRT) is an example of a NDBI. The key assumption of PRT is trying to teach pivotal skills to children. It states that when learning occurs with these skills, natural learning will occur in other areas. Motivation to respond to social and environmental stimuli is essential for typical development but children with ASD may fail to understand the interconnection between their behaviour and the consequences from their environment as a result of repeated failures and non-contingent assistance and reinforcement from adults. This can lead to learned helplessness. PRT aims to decrease learned helplessness by enhancing the relationship between children’s responses and reinforcement.

This can enhance motivation and this may lead to a positive feedback loop where more learning opportunities are provided, which may generate the social-environmental conditions for the development of more complex behaviours.

It focuses on several pivotal skills:

• Motivation for interaction (i.e. most important).
• Self-initiation (i.e. this can lead to more opportunities for learning).
• Joint attention
• Responsivity to multiple stimuli.
• Self-regulation.

Children with ASD are often unmotivated to socialize but are motivated to engage with non-social aspects of their environment. The salient characteristics of non-social interests may be identified and embedded within a reciprocal social activity. This can enhance motivation to socialize. Incorporating restricted activities in mutually-reinforcing social activities can lead to intrinsic motivation for social play.

Parents should also deliver PRT to provide consistency for the child. There is a greater treatment effectiveness when it is delivered by parents compared to clinicians. They receive direct feedback from the therapist while working with the child on the following:

• Use of child-selected stimulus materials.
• Direct, natural reinforcers are used whenever possible.
• Interspersing maintenance trials (i.e. intersperse previously learned tasks with new tasks).
• Reinforcing attempts of the child.

The Early Start Denver Model (ESDM) is another example of a NDBI and is based on ABA, PRT and social motivation hypothesis. The goal is to accelerate children’s developmental rates in cognitive, social-emotional, language, and adaptive domains and to reduce the disabling effect of ASD symptoms. The focus of the treatment is on children between the ages of 12 and 60 months. The treatment takes place within naturalistic settings.

There are several components:

• Building close relationships with the children and between the children and others in their environment.
• Using sensory social routines (e.g. seeking out social partners; initiate routines).
• Teaching play and imitation.

It aims to utilize imitation to teach skills in other domains. ESDM enhances the reward value of social interaction. Each treatment objective is broken down into several teaching steps based on a task analysis of the skill (i.e. the child’s current baseline level and ending with a fully mastered and generalized skill).

The social motivation hypothesis states that children with ASD have an impaired sensitivity to reward value of social stimuli. This leads them to pay reduced attention to social stimuli. The reduced attention, in turn, leads to fewer learning opportunities.

There are different versions of ESDM:

• Intensive delivery (i.e. 20 hours per week, one-to-one, 2 years)
  There are large improvements in IQ (1), adaptive behaviour (2), language (3) and ASD severity (4).
• Parent coaching (i.e. 1 hour per week, 12 weeks).
  This teaches parents to use ESDM techniques in everyday interactions and there seem to be positive effects for this treatment.
• Preschool/daycare delivery (i.e. 12-25 hours per week, group setting).
  This seems to lead to developmental and language improvement.

People participating in ESDM maintained gains in early intervention for 2 years in intellectual ability (1), adaptive behaviour (2), symptom severity (3) and challenging behaviour (4). ESDM is associated with improvements in brain activity (e.g. enhanced brain activity in regions related to social processing; greater cortical activation while viewing faces). There are three potential neural mechanisms of ESDM:

• Neural plasticity
  This is very high early in life and ESDM capitalizes on this.
• Dopaminergic pathways
  ESDM increases the reward value of social stimuli by adjusting dopaminergic pathways in the brain.
• Neural functional connectivity
  ESDM promotes functional connectivity and treats ASD as a ‘disconnection syndrome’.

The recommendation is that children should receive 20 hours per week for two years of ESDM. The treatment should thus be very intensive. However, there are several barriers to intensive interventions:

• Shortage of qualified providers
• Geographic area without adequate service availability
• No funding for interventions
• Culturally and linguistically diverse populations.

The parent-child education programme is a less intensive treatment based on ESDM. In this treatment, parents master the strategies and this leads to sustained change and growth in social communication behaviours. This allows the treatments to be less intensive. The parents learn to focus on the child and the interaction more. There are mixed findings for the efficacy of 12-week online parent training based on ESDM.

Single-case studies demonstrate the effective components of manualized treatments but using a different order of delivering the components and using frequent assessment. Important components (i.e. techniques) include stepping into the attentional spotlight of the child (1), talking to the infant (2) and imitation (3).

An intervention is more useful when it starts at a younger age:

• Intervention before age 3: 95% becomes verbal.
• Intervention between age 3 and 5: 85% becomes verbal.
• Intervention after age 5: 20% becomes verbal.

The reduces effectiveness with age may be due to reduced brain plasticity and this suggests the existence of a critical period. ASD symptoms (e.g. aggression; tantrums; self-injury) often have a communicative function. As early intervention improves verbalization, these secondary symptoms may reduce. Similarly, comorbid symptoms are often related to difficulties with socialization and this is improved with early intervention.

Early intervention could also provide parents with tools to address symptoms and this could lead to more self-confidence and a feeling of empowerment, which is useful as a child with a disability leads to a lot of stress. These tools could improve parenting.

ESDM leads to positive results when it is administered to infants. One-on-one interventions delivered at home are very effective for children with autism due to the generalization of skills. However, starting treatment early is difficult as screening for ASD in very young children is often very difficult for several reasons:

• ASD is defined by behaviour and not all infants show problematic behaviour.
• There are no infant screeners that are good at predicting later diagnosis.
• Symptoms associated with ASD in infants under 12 months of age are not specific to ASD.

There is a different treatment goal and approach for different target symptoms in ASD: