The data in the included studies were collected over a period of > 40 years (from around 1968 to 2011), during which time the understanding, diagnosis and management of autism has evolved significantly. Consequently, there is noticeable variation between individual studies in terms of the delivery of interventions and comparators, the conceptualisation of autism and the outcomes of interest. As well as differences between the studies, there may be important differences between this body of evidence and the context in which early intensive ABA-based interventions and other treatment alternatives may be delivered in the UK in the future.
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Interventions
Content, delivery and expertise
The original EIBI study by Lovaas at UCLA26,98mainly employed discrete trial training, with some
generalisation activities and community outings. Contingent physical aversives (the delivery of a loud ‘no’ or slap on the thigh) were employed as a last resort. As noted in Chapter 9, later variations in early intensive ABA-based interventions have incorporated more naturalistic components in their delivery and discontinued the aversive contingencies used in the original UCLA EIBI approach. Corporal
punishment has been illegal in the UK for > 30 years and physical aversives have long been abandoned as part of ABA-based intervention delivery. Although all interventions included in this review had a theoretical basis in ABA, their content and delivery has evolved over time.
The UCLA EIBI intervention was delivered by trained student therapists, overseen by the study authors who were based at a specialised university centre, ensuring a high level of resource and expertise being made available to children and their families.26Smith et al.103reported 10 years’ experience working at
the UCLA Young Autism Project. Similar expertise was available in the randomised study of the ESDM, which also involved the authors who developed the intervention method.83,106,107,112
The original narrow definition of what once constituted ‘true’ EIBI may not resemble very closely what is delivered in the current UK context, in which the intervention is more likely to be informed by more naturalistic approaches and delivered in a home or community setting, without the resources of an expert university research centre to train and supervise treatment staff.
Intensity and duration
The original UCLA EIBI was highly intensive. In addition to children receiving an average of 40 hours per week of one-to-one contact with therapists in their home, school and community for at least 2 years, parents were asked to take a year off from their current employment103and were trained so that ‘treatment
could take place for almost all of the subjects’ waking hours, 365 days a year’.26Although actual treatment
intensity and duration data were not recorded for individuals, it would appear that children had around 4 years of treatment on average (based on reported age at recruitment and follow-up), with children who had not ‘recovered’ continuing to receive > 40 hours per week of one-to-one teaching with therapists for > 6 years.26
As stated in Included studies, subsequent studies of early intensive ABA-based interventions were more varied in intensity and duration. Interventions rarely exceeded Lovaas’ minimum requirement of 40 weekly hours of one-to-one teaching.26For example, authors who had been involved in the UCLA
programme have delivered forms of EIBI that are deliberately less intensive than originally proposed (30 hours/week rather than 40 hours/week, with treatment phased out after 18 months if progress was slow).103Other studies have shown intervention hours to substantially reduce after the first
2 years of treatment83,106,107,112or when children started school.85,95Although IPD on actual intensity
were largely unavailable, the average weekly hours of teaching reported in UK studies ranged from 25.692,110to 37.499hours per week, and ranged from 13.6 to 38.6 hours per week in other studies.
As well as a possible impact on effectiveness, the duration and intensity of ABA-based treatment has implications for resource use (e.g. staffing costs) and possibly setting. Children in the UK typically start school at 5 years of age, whereas much of the evidence included in the current meta-analysis is from countries in which the primary or elementary school starting age is 6 years (USA, Norway, Canada, Israel). So in other countries, EIBI has been delivered in home and/or nursery or preschool settings, but in the UK it may be given in a primary education environment.
Another issue is that of the intervention supervision and management model. Several EIBI studies described the intervention being delivered by tutors who received ongoing training and feedback from supervisors, who in turn were overseen by a consultant or clinic director.26,103However, this form of management is
Comparators
Comparator interventions for autistic children have also evolved over time, with the emergence of autism-specific rather than generic special needs care. More recently, ‘eclectic’ comparators have explicitly incorporated some ABA techniques.83,84,86,89,93,94,96,97,105,108,109In most studies, children in the
eclectic or TAU comparator arms received fewer hours of intervention and/or less one-to-one contact. However, this was not always the case: Howard et al.105,108compared EIBI against an eclectic autism-
specific classroom, with ≈30 hours per week of one-to-one or one-to-two intensive intervention; and Zachor et al.94,97reported both intervention groups receiving similar levels of funding per child, hours in
preschool setting, support for parents and staff, and individual one-to-one treatments.
Although we did not restrict inclusion by comparator, all of the identified comparators were eclectic intervention or TAU; no studies compared early intensive ABA-based interventions with discrete medical or educational interventions.
It is difficult to map the comparators in the available evidence to the current UK standard provision for two reasons. First, most studies had very limited available information on the content of eclectic interventions or TAU, as the study investigators were rarely involved in their delivery. Second, there is evidence that standard provision in the UK differs substantially between local authorities, although information obtained from York local authority suggests a mix of therapies not dissimilar to those cited in the studies (Ruth Horner, City of York Council, York, 2018, personal communication).
Participants
The studies included in this review cover a period when a large increase in the annual incidence of autism has been observed (more than fivefold from 1988 to 1995).113,114Part of that increase has been attributed
to changing and broadening diagnostic criteria,115,116as well as increased medical and public awareness.117
This raises concerns about whether or not children receiving early intervention ABA-based interventions in included studies are similar to those currently eligible for intervention in the UK.
The overall population of children for whom IPD were provided were young (mean age 38 months) with mild-to-moderate intellectual disability (mean IQ 57) (see Chapter 6, Individual participant data received from included studies). As all children had to have an established diagnosis of autism or related condition to participate in the included studies, the study populations ought to be comparable to those who would be eligible for treatment in the current UK context. However, some of the more highly controlled studies excluded children with comorbidities, so it is plausible that typical UK treatment populations are more heterogeneous than those in the available evidence.
Outcomes
Although we accepted any outcomes for the IPD meta-analysis, only a small number of outcome domains were consistently collected across the included studies (most commonly, verbal and non-verbal IQ, adaptive behaviour and language measures; less commonly, autism symptom severity, behaviours that challenge and school placement).
The original Lovaas study26,98was almost entirely focused on IQ and mainstream schooling placement as
measures of treatment success. Children who achieved IQ in the average range were considered ‘recovered’ and the authors made ‘considerable effort’ to keep these children in mainstream preschool. In some cases, this involved withholding the child's diagnosis of autism. The authors stated, ‘If the child became known as autistic (or as “a very difficult child”) during the first year in pre school, the child was encouraged to enrol in another, unfamiliar school (to start fresh)’.26Apart from any ethics and bias concerns it may raise,
this excerpt shows how different the goals of early autism interventions were 30–40 years ago.
Subsequent studies incorporated behavioural measures, such as adaptive behaviour, while retaining IQ or cognitive development measures. Schooling as an outcome was only collected in a minority of studies and did not use consistent classifications.26,89,92,96,98,103,104,109,110
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Outcomes relating to social participation, well-being and quality of life were not measured among the included studies. Although measures of cognitive development and adaptive behaviour can be used to track progress and development, no studies investigated how these measures correlate with measures of well-being, either during treatment or in the long term. In fact, any measurement of outcome beyond the end of the early intervention treatment period was rare.
With the exception of one study stating that ‘no serious adverse effects related to the intervention were reported during the 2-year period’,83,106,107,112adverse or unintended effects of intervention were
not addressed in the available evidence, with no study providing IPD on adverse effects.
The selection of measurement tools used for the collected outcomes varied within and between studies. Different measures of IQ and cognitive development were used at baseline and follow-up, based on the relevant normative populations [e.g. the WPPSI-R67or BSID scales at baseline and Wechsler Intelligence
Scale for Children (WISC)65at follow-up]. At baseline, in particular, decisions about which measure to use
are also informed by children’s developmental skills and ability to meaningfully be assessed in particular tests. The IPD meta-analyses separate measures of non-verbal skills (such as the MPSMT)70from
standard intelligence tests, which include verbal and non-verbal scales, as the former are known to yield higher scores.100
Several studies reported difficulties when using standardised measures in the evaluation of interventions in young autistic children, including floor and ceiling effects on different tests at different ages. Authors dealt with these difficulties by recording minimum or maximum scores,103reporting age-equivalent
scores,101raw scores89,92,96,109,110or the number of children capable of achieving a score.92,110Although the
provision of IPD facilitated the harmonisation and synthesis of scores across some of these studies, this was not always possible or appropriate.
Most studies provided standard scores when these were available and these scores informed the IPD meta-analyses. However, although standard scores allow comparisons with typically developing populations, it has been argued that they may miss information about changes that are relevant within the autism population specifically.118This problem is not limited to early intensive ABA-based interventions, but is