|"You built a time machine.. out of a DeLorean"|
That was the conclusion arrived at in the paper by Ting-Yang Lin and colleagues . For regular readers of this blog, this was yet another example of how Taiwan leads the way when it comes to the concept of 'big data' specifically employed with neurodevelopmental conditions in mind. That Taiwan National Health Insurance Research Database is proving to be a very valuable resource indeed.
A few details from the latest study:
- "5386 children aged less than 18 years with ADHD alone, 578 with ASD alone, 458 with ADHD + ASD, and 25,688 non-ADHD/ASD age- and sex-matched (1:4) controls were enrolled in our study". I don't think anyone can say that this was an underpowered study.
- The presence of various allergic diseases including asthma and atopic dermatitis were looked at among participant groups and compared.
- Results: Odds ratios (ORs) suggested that the autism, ADHD and combined autism + ADHD groups were all more likely to present with comorbid allergic conditions compared to asymptomatic controls. This, taking into account "age, sex, and level of urbanization". The combined group seemed to be a greater risk of allergic disease than the autism or ADHD alone groups (OR: 2.2 95% CI: 1.83–2.79).
- "ASD children with more allergic comorbidities were associated with a greater likelihood of ADHD".
Quite a bit of this data taps into previous findings based on the examination of the Taiwanese insurance database insofar as the link between asthma (see here and see here) and neurodevelopmental diagnoses, so no real surprises there. The intriguing prospect that an increasing allergic burden in cases of autism seemed to elevate the risk of comorbid ADHD being present is the value-added part to the Lin study. What autism research is starting to understand is that comorbidity is quite a big issue (see here) and, outside of learning disability (see here) and epilepsy (see here), ADHD seems to figure quite prominently (see here).
Bearing in mind that correlation is not the same as causation, I'd like to see quite a bit more investigation into that autism - allergy - ADHD relationship talked about by Lin et al. Genetics might be a good starting point as per the growing realisation about 'common ground' when it comes to various behaviourally-defined conditions (see here). The recent paper looking at the possible genetics of schizophrenia  linking into immune functions (see here) might set the tone for further inquiry in this area. Given the growing body of research looking at immune function and autism (see here and see here for examples) one might see how allergic diseases may show more than a passing connection to at least some cases.
I'd also be minded to suggest that environment might also be something to look at with this possible relationship in mind. Food is something of a potential common denominator when it comes to at least some autism and some ADHD (see here) so perhaps further investigation might be required there. The paper by de Theije and colleagues  talked quite a bit about food allergy and autism and ADHD for example. I don't know enough about how food might tie into something like asthma or atopic eczema as to present any knowledgeable information about links. I'd hazard a guess that looking at something like the gastrointestinal (GI) tract and things like the gut microbiota  might also be worthwhile.
Music to close, and something uplifting from The Smiths...
 Lin T-Y. et al. Autistic spectrum disorder, attention deficit hyperactivity disorder, and allergy: Is there a link? A nationwide study. Research in Autism Spectrum Disorders. 2014; 8: 1333-1338.
 Schizophrenia Working Group of the Psychiatric Genomics Consortium. Biological insights from 108 schizophrenia-associated genetic loci. Nature. 2014; 511: 421-427.
 de Theije CG. et al. Food allergy and food-based therapies in neurodevelopmental disorders. Pediatr Allergy Immunol. 2014 May;25(3):218-26.
 Molloy J. et al. The potential link between gut microbiota and IgE-mediated food allergy in early life. Int J Environ Res Public Health. 2013 Dec 16;10(12):7235-56.
Lin, T., Lin, P., Su, T., Chen, Y., Hsu, J., Huang, K., Chang, W., Chen, T., Pan, T., Chen, M., & Bai, Y. (2014). Autistic spectrum disorder, attention deficit hyperactivity disorder, and allergy: Is there a link? A nationwide study Research in Autism Spectrum Disorders, 8 (10), 1333-1338 DOI: 10.1016/j.rasd.2014.07.009