The Relationship Between Duration and Outcomes in Young Children on the Autism Spectrum Using a Specialised Intervention

Background: Previous research has shown that early intervention results in improved outcomes for children on the Autism Spectrum. However, there is limited data and mixed findings on the impact that duration of time spent in therapy has on treatment outcomes. While some studies have shown that minimal significant gains occur after one year of intervention, others have indicated that children receiving more specialised interventions demonstrated marked improvements with increased time spent in therapy (Cohen, Amerine-Dickens, & Smith, 2006; Howard, Stanislaw, Green, Sparkman, & Cohen, 2014; Virues-Ortega, Julio, & Pastor-Barriuso, 2013). These researchers argue that specialised interventions are generally focused on building foundational skills within the first year, while the second year helps to further develop and solidify these skills (Howard et al., 2014). Although there are a few interventions classified as specialised, to date, much of the research has focused on Applied Behaviour Analysis. Therefore, it is important to investigate whether this finding is limited to ABA or extends to other specialised therapies.

Objectives: The objective of the current study was to evaluate the relationship between duration of a specialised intervention, specifically the Early Start Denver Model (ESDM), and outcomes including symptoms of autism, cognitive ability and adaptive behaviours.

Methods:  Children on the autism spectrum were aged two to five attending an autism specific preschool program receiving the ESDM early intervention program were evaluated at the beginning of the intervention program, and followed up every 12 months until they exited the preschool. Correlation and Regression analysis were used to assess the relationship between months children spend in therapy and outcomes in assessments. These included the Autism Diagnostic Observation schedule, the Mullen Scales of Early learning, Vineland Adaptive Behaviour Scales, Social Communication Questionnaire and the Repetitive Behaviour Scale.

Results: Increased time spent in therapy was associated with improved outcomes across a number of domains after controlling for potential moderators, including cognitive ability, age at enrolment, severity of symptoms and intensity of intervention. These included communication skills, daily living skills, interpersonal relationships, coping skills and adaptive behaviours. Interestingly, there was no association between improvement in receptive and expressive language and the duration of intervention.

Conclusions: Our findings demonstrate that early intervention is beneficial for preschool children on the autism spectrum, with increased duration of specialised intervention associated with improved outcomes across specific domains of functioning. These associations are in keeping with the domains that were the target of the intervention. However, further improvements in receptive and expressive language were not associated with the duration of intervention. It is unclear whether this finding indicates that children received the maximum benefit on receptive and expressive language skills after the first year of intervention or whether other factors outside of the ones accounted for played a role. Overall, this study supports the idea that increased time spent in specialised interventions improves specific outcomes.