Access to early intervention (EI) has been identified as a priority for global research in developmental disability (Collins et al., 2017;Tomlinson et al., 2014). As a term, developmental disability refers to several developmental conditions but especially developmental delay, intellectual disability and autism spectrum disorder (ASD) 1 .The onset of developmental disabilities takes place during early development and lasts throughout an individual's lifetime (Patel & Merrick, 2011). Whilst the individual needs of children with developmental disabilities are unique, general delays in cognitive and adaptive skills are present by definition (American Psychiatric Association, 2013;Carulla et al., 2011;McDonald et al., 2006). A range of other adverse outcomes are associated with developmental disabilities, such as poorer mental health, poorer physical health and social inequalities (Emerson, 2003;Emerson & Hatton, 2007;Gurney et al., 2006;Vasilopoulou & Nisbet, 2016). For example, an increased risk for behaviour problems is present in children with developmental disabilities as young as 3-5 years old (Totsika et al., 2011), and this increased risk persists into adolescence and adulthood (Gray 1 While autism spectrum disorder (ASD) is predominately used in the current paper in line with the Diagnostic and Statistical Manual of Mental Disorders-5, other autism diagnostic labels (Asperger syndrome, autism, Pervasive Developmental Disorder Not Otherwise Specified, Rett syndrome, autistic traits) are used to describe studies completed in the context prior to the widespread use of ASD as an all-encompassing autism diagnosis in instances where autism diagnostic label is pertinent to the findings.