I'm pretty sure that the topic of developmental regression and autism needs no further introduction. Suffice to say that as the name suggests, it's all about a loss of previously acquired skills and how this might map on to some of those 'autisms' that I seem to talk about quite a lot. After a bit of a laboured start (see here) there is now a general acceptance that regression can occur in cases of autism and sometimes pretty rapidly (see here) although I hasten to add, not seemingly present for everyone with autism.
I have to thank Natasa for passing me a full-text copy of the Goin-Kochel paper, and without further ado, here are a few of the main points:
- The SSC was the source for participants, which meant that diagnoses of autism or autism spectrum disorder (ASD) were about as reliable as one could hope for. Interestingly, the authors do make mention of the whole DSM-IV to DSM-5 transition and what that might mean for databases such as the SSC but that's perhaps fodder for another day.
- "Regression was operationalized using the skill-loss items from both the ADI-R and a supplemental interview that captured information about additional and more subtle skill losses". I've talked before about how ADI-R was a really important contributor to raising the profile of regression and autism as a function of it including items about 'loss of language/other skills'. In this case, researchers defined various types of 'loss' to include codings such as 'full losses' and 'subthreshold losses'. They also analysed data according to "skill loss at/before 36 months and those who experienced skill loss after 36 months".
- Results: "Overall, 36.9% of children had some type of regression". Such regression included a regression in language and/or other skills and included those with full losses and those with subthreshold losses. Another quote: "When combined, 585 (27.8%) children experienced some degree of language loss and 568 (27.0%) experienced some degree of other loss".
- The authors focused quite a lot on the pre-36 months loss side of things as a function of quite a lot of discussion on age of first parental concern being rooted in that critical period. So: "those with any degree of language loss (full or subthreshold) at/before 36 months scored significantly lower than those with no language loss" when looking at how regression might affect "cognitive and adaptive-functioning outcomes".
- Finally, a couple of other important details to mention: (a) "subthreshold losses of other skills occurred later than any type of language regression and later than full losses of other skills", and (b) duration of loss of skills is also discussed: "most children regained their skills by 3.5-5 years of age". They conclude that their study: "lends support to the argument that children whose parents report regression represent a distinct ASD subtype that may be associated with lower cognitive functioning".
The participant group size and the use of the SSC are important features which make these results something to shout about. Alongside the meta-analysis by Barger and colleagues  autism research is beginning to build up quite a good picture on the rate of regression being reported in the autism research literature and some details on presentation and even outcome.
That being said, there is still an awful lot more to do in this area. The Goin-Kochel did not set out to look at "etiological mechanisms" but the next stage in this research should surely be further study which looks at possible correlates to such regressive accounts. I wouldn't necessarily agree with the sentiments of the authors when they say: "An acknowledged limitation of this study is its reliance on parent-report data" especially when it comes to parent report and other issues such as gastrointestinal (GI) problems (see here) and the conclusions reached by Phillip Gorrindo and colleagues  (open-access here). Recall may well be affected by things like telescoping effects (see here) but in these days of home movies  and the rise of social media, many infants see the end of camera lens very, very early following their entry into the big wide world. Where regression occurs, I'm sure many parents would have their own ideas about the hows and whys which could be investigated including some slightly more biological / genetic based investigations .
I've two more points to make on this study and research area and that's all. First is an issue which the authors touch upon in their discussion of their results: "... the SSC is largely comprised of Caucasian families". The recent abstract from Adiaha Spinks-Franklin and colleagues (which, at the time of writing, I don't yet think is published in a peer-reviewed form) hints at some racial differences in the occurrence of regression in autism. The question is whether this might also translate into a different pattern of regressive symptoms and indeed, any different effects on longer term outcome?
Second is that issue of long-term outcome. As we're starting to see with the optimal outcome work (see here), longitudinal studies looking at outcome from all those developmental trajectories which make up the autisms is starting to yield some interesting results. The next question would be whether similar studies looking at regressive vs. non-regressive presentation (even different types of regression ) would similarly provide important data on the extent to which regression might affect future development and presentation and ways these could be positively affected. I'd also add that looking at any effects from regression on comorbidity outside of the core dyad of symptoms might also be included in any future work knowing what we (think we) know about this important issue.
To close, Katy Perry and Last Friday Night (a song my brood are really enjoying at the moment).
 Goin-Kochel RP. et al. Developmental regression among children with autism spectrum disorder: Onset, duration, and effects on functional outcomes. Res Autism Spectr Disord. 2014; 8: 890-898.
 Barger BD. et al. Prevalence and onset of regression within autism spectrum disorders: a meta-analytic review. J Autism Dev Disord. 2013 Apr;43(4):817-28.
 Gorrindo P. et al. Gastrointestinal dysfunction in autism: parental report, clinical evaluation, and associated factors. Autism Res. 2012 Apr;5(2):101-8.
 Palomo R. et al. Autism and family home movies: a comprehensive review. J Dev Behav Pediatr. 2006 Apr;27(2 Suppl):S59-68.
 Shoffner J. et al. Fever plus mitochondrial disease could be risk factors for autistic regression. J Child Neurol. 2010 Apr;25(4):429-34.
 Ozonoff S. et al. Parental report of the early development of children with regressive autism: the delays-plus-regression phenotype. Autism. 2005 Dec;9(5):461-86.
Goin-Kochel, R., Esler, A., Kanne, S., & Hus, V. (2014). Developmental regression among children with autism spectrum disorder: Onset, duration, and effects on functional outcomes Research in Autism Spectrum Disorders, 8 (7), 890-898 DOI: 10.1016/j.rasd.2014.04.002