|Seasons: Autumn @ Wikipedia
Their naturalistic study suggested that the very early years of autism, at least some autism, and its presentation are characterised by "considerable change over time" and the requirement for "follow-up assessments" in order to more accurately measure where the sands of autism have settled prior to the start of school.
Their reporting that intellectual disability (ID) also might have a maturational aspect to its appearance alongside cases of autism (i.e. not common in early diagnosis but present in about 50% of cases at follow-up) also provides some food for thought in terms of whether this reflects a specific comorbidity or indeed, something more central to specific types of autism (yes, the autisms), though carrying a different timescale of presentation.
I'm not altogether sure but I think we might have seen the Hedvall cohort used in another study by Fernell and colleagues** during their study looking at early intervention and autism. In that paper, the same number of preschoolers with autism (N=208) were followed "in a naturalistic fashion" and their various experiences of an ABA (applied behaviour analysis) program recorded. If it is one and same cohort, it's likely then that we are probably not talking about developmental changes occurring just spontaneously in some sort of intervention vacuum. Sort of what happens in real-life.
I've talked before on this blog about diagnostic stability and instability when it comes to autism (see here). Whilst accepting that 'universals' when it comes to autism are generally few and far between outside of the almighty diagnostic criteria, the conclusion reached on that post was that stability with regards to a diagnosis of autism is surprisingly, quite an unstable thing. When particularly applied to the early years and their growing importance when it comes to autism (see here) one might speculate that such instability presents its own issues particularly in these times when chatter about really early autism diagnosis is becoming more frequent and louder and louder. Discussion about the important issue of regression which might also interfere with any notion of a universal prenatal or early autism diagnostic test is also worth noting. That also different children on the autism spectrum might present with different developmental trajectories is an important point to emphasise, particularly in these times of optimal outcomers for example (see here).
Whilst the Hedvall data provides a cautionary tale that we should be mindful of how dynamic autism might be in the early years (and perhaps even beyond), I'd like to think that it won't be used as an excuse for delaying assessment and diagnosis too much and the subsequent impact that can have....
* Hedvall A. et al. Autism and developmental profiles in preschoolers: stability and change over time. Acta Paediatr. 2013 Oct 8. doi: 10.1111/apa.12455.
** Fernell E. et al. Early intervention in 208 Swedish preschoolers with autism spectrum disorder. A prospective naturalistic study. Res Dev Disabil. 2011 Nov-Dec;32(6):2092-101.
Hedvall A, Westerlund J, Fernell E, Holm A, Gillberg C, & Billstedt E (2013). Autism and developmental profiles in preschoolers: stability and change over time. Acta paediatrica (Oslo, Norway : 1992) PMID: 24237479