Monday 28 March 2016

The genetics of self-injurious behaviour accompanying autism? Not quite...

I'd like to start by making one thing abundantly clear about today's post: I am not insinuating that self-injurious behaviour (SIB) accompanying autism is solely under genetic (or epigenetic) control.

As I've discussed before on this blog, there are potentially many, many reasons why SIB under the umbrella of the so-called 'challenging behaviours' occurs (see here). As and when it does happen, the onus is on those significant others to turn detective before anyone immediately reaches for something like the anti-challenging behaviour meds (see here) or indeed makes any sweeping generalisations about it 'just being part of their autism'. I say this mindful that sometimes it can seemingly be the smallest things that can trigger such episodes...

The findings reported by Matthew Shirley and colleagues [1] (open-access) do however require some attention with the idea that certain genetic issues *might* "contribute to the etiology of SIB." The specific genetic issues under the research spotlight were copy number variants (CNVs) and authors were looking at quite a precise cohort of children/young adults diagnosed with "autism and intellectual disability with self-injurious behavior (SIB) resulting in tissue damage" (N=14). I might add that CNVs with autism and learning disability in mind have some history (see here).

Based on quite a thorough work-up (including a functional behavioural assessment), researchers zoomed in on 4 children (29%) where they identified "a CNV likely to have a causal role" in SIB. I'm afraid my very limited knowledge of genetics precludes any critical discussion about the nature or role of any individual genetic issues reported but I might backtrack slightly based on something the authors write regarding 'causality': "the present findings are not able to indicate definitively that any of these variants is causal." Apparently we need to wait for more data from additional patients with the same/similar clinical phenotype before much more can be said on this issue. Indeed: "it is likely that exome or genome sequencing will greatly increase the diagnostic yield of the cohort we are studying."

Perhaps just as important as the question of whether genetics plays a role in a complex behaviour pattern like SIB are the authors' observations of what might have triggered SIB in their participants. The authors talk about the results of the very important functional behaviour assessments as revealing some common themes: "SIB was multiply maintained by escape from demands and access to preferred toys... SIB was multiply maintained by access to preferred foods and access to attention... Head-banging was found to be maintained by access to preferred foods... Head-hitting, self-biting, and head-banging against hard surfaces were observed to be maintained by automatic reinforcement." What these excerpts tell me is that SIB could potentially be a communicative act, bearing in mind details of language and communication 'level' of participants are fairly scant in the Shirley paper. As I've talked about previously (see here), issues such as fatigue and setting event are also potentially important parameters when getting to the bottom of SIB and other challenging behaviours.

The final question, and perhaps an important one when one realises just how extreme an effect SIB can exert (see here), is 'what can be done about reducing levels of SIB' when they present.  Well, working out the hows and whys of such behaviour should be the first strategy, and can sometimes yield impressive results. Although I suggested at the beginning of this post that the 'anti-challenging behaviour meds' should be a further-down-the-list resort, there is evidence that they can be helpful for some people in some situations assuming appropriate medicines management and monitoring for potential side-effects (see here). With no medical or clinical advice given or intended, I'd also be minded to direct readers to some research looking at adjuvant therapies such as the use of N-acetylcysteine (NAC) where issues like irritability might show some connection to SIB (see here and see here) or even something of particular interest to me, the use of naltrexone (see here). More research is indicated and indeed, quite a lot more with much greater participant numbers before anyone starts on about having identified the genetics of SIB in autism...


[1] Shirley MD. et al. Copy Number Variants Associated with 14 Cases of Self-Injurious Behavior. PLoS ONE. 2016; 11: e0149646.

---------- Shirley, M., Frelin, L., López, J., Jedlicka, A., Dziedzic, A., Frank-Crawford, M., Silverman, W., Hagopian, L., & Pevsner, J. (2016). Copy Number Variants Associated with 14 Cases of Self-Injurious Behavior PLOS ONE, 11 (3) DOI: 10.1371/journal.pone.0149646

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