Indeed, the paper by Megan Tudor and colleagues  which makes up the material for today's post, adds to that message with their report on pain as being a predictor of sleep problems for some children/young adults with autism. Once again, my thanks go to Natasa for providing the full-text version of the paper for my blogging consumption (yum!).
The long-and-short of the Tudor paper was as follows:
- Take two issues which have cropped up in the autism research literature more than once - sleeping issues and pain - and aim to examine "pain-related behaviors as a predictor of sleep problems in youth with parent-reported ASD using standardized parent-report measurement of both variables".
- Mothers of a sample of 62 children/young adults drawn from a larger study  [note to authors, your date is wrong for this reference] were questioned using several measures including the NCCPC-R (see here) and the CSHQ  (open-access) looking at pain and sleep respectively. I should also note that questionnaires were completed on-line and participants received a financial incentive to complete [a large chunk of] questionnaires.
- Results: parent-reported participant pain levels according to NCCPC-R scores "was high compared to normative information for this measure". Sleep issues were similarly elevated in the sample, particularly parasomnias. The discussion notes that pain scores were gathered across a slightly different timespan to the normative data (1 week retrospective report for the study vs. 2-hour observation period for the normative data) so one perhaps need to be a little cautious about this.
- Some regression analysis for scores on the two instruments revealed some potentially important results. So higher pain scores "predicted higher scores on CSHQ Total Sleep Disturbance" although with an R-squared value of 0.22 this is not necessarily a straight-forward connection.
- Specific sleep problems including sleep duration, parasomnias and sleep-disorder breathing were also reported as being accompanied by a previous weeks pain-related behaviours and may well have had some very individual behaviours linked to them e.g. "problems with sleep duration were predicted by social communication of pain, such as comfort-seeking and being difficult to pacify" and "Parasomnias were predicted by facial communication of pain, such as grimacing or brow furrowing".
- The authors conclude that whilst there is more to do in this area of investigation (including the important use of control groups) their results should serve as a marker for healthcare professionals when dealing with children with autism who also present with sleeping issues. To quote: "how pain and sleep problems relate to one another and may affect children's daytime functioning...". This may have some far-reaching effects in terms of how sleep issues are traditionally managed when it comes to autism and other developmental disorders.
Going back to the my starting paragraph about autism not being to blame for every single behavioural manifestation noted among cases, I can't help but ask the question: why were parent-reported indicators of pain-related behaviours seemingly elevated in this sample? As far as I know - and I am just an outsider looking in - autism is not necessarily defined as a painful condition. Indeed, even the authors point to the possibility of a "high threshold for pain"  described in the DSM-IV TR diagnostic schedule for autism. Certainly if it was shown that autism 'is a painful condition', it would perhaps change some of the dialogue noted in Dr Insel's Four Kingdoms of Autism.
I do have a few theories about this notion of pain and autism however so bear with me. Tudor and colleagues allude to one of them insofar as discussions about "ongoing mild digestive discomfort" and "severe inflammatory bowel disease" with both issues having cropped up before on this blog previously. Thinking back to the paper by Kushak and colleagues  discussed in this post on lactase enzymes and autism, there is the suggestion that lactose intolerance (related to the sugar found in milk and dairy produce) "may contribute to abdominal discomfort, pain and observed aberrant behavior". With autism and inflammatory bowel disease in mind, the Walker paper  published a while back (discussed in this post) springs to mind.
Of course, I don't claim that every expression of pain noted in autism is necessarily one of being related to gastrointestinal (GI) function or dysfunction but one could certainly look to rule these issues out if one were being assiduous. As per some other potentially important issues, I might also refer you to a post I wrote a while back on self-injurious behaviour (see here) and other areas that one might look at when it comes to pain being potentially present in cases of autism.
The final angle that is perhaps worthy of exploration has already been touched upon in the additional reference by Allely  (see here again) in relation to how one of the core aspects of autism might itself have the ability to induce pain: sensory sensitivity. I say core aspect but am referring to the recent inclusion of sensory issues into DSM-V noting that not everywhere in the world has made the shift over the DSM-5. So, things like over sensitivity to sound for example, I assume may register on someone's behaviour and manner, just as issues with the visual modality might also have the ability to induce something like pain (see here). Indeed, migraine might be something else to look at with pain and autism in mind  and not just with the head in mind either . As per previous statements, it all depends on how far one is willing to look into the issue of pain and the potential reasons for its presence...
 Smith MD. et al. Autism and Obstacles to Medical Diagnosis and Treatment. Focus Autism Other Dev Disabl 2012; 27: 189-195.
 Tudor ME. et al. Pain as a predictor of sleep problems in youth with autism spectrum disorders. Autism. 2014 Feb 4. [Epub ahead of print]
 Walsh CE. et al. Predictors of parent stress in a sample of children with ASD: Pain, problem behavior, and parental coping. Res Autism Spec Disorder. 2013; 7: 256-264.
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 Kushak RI. et al. Intestinal disaccharidase activity in patients with autism: effect of age, gender, and intestinal inflammation. Autism. 2011 May;15(3):285-94.
 Walker S. et al. Identification of unique gene expression profile in children with regressive autism spectrum disorder (ASD) and ileocolitis. PLoS ONE. 2013; 8: e58058.
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Tudor ME, Walsh CE, Mulder EC, & Lerner MD (2014). Pain as a predictor of sleep problems in youth with autism spectrum disorders. Autism : the international journal of research and practice PMID: 24497628