asthma and autism on this blog. It's not that it isn't an interesting topic but rather that the data is coming in thick and fast suggesting that behaviour and physiology are not completely separate anymore.
I did however want to direct you to the paper by Alessandro Tonacci and colleagues  who, following a systematic review "according to the PRISMA guidelines" suggested that "Autism Spectrum Disorder and asthma could be associated conditions, as evidenced by the higher prevalence of asthma in autistic children with respect to typically developed controls." I might add that this is not the first time that this authorship group have examined the coincidence of allergic disease with autism (see here).
The idea that asthma and autism might be connected is an important finding because not so long ago I talked about another paper  - a meta-analysis - that came up with a slightly different conclusion to that listed by Tonacci (see here). OK, a systematic review and a meta-analysis whilst related are not necessarily one and the same and so one has to be a little careful. That being said, I did raise a few 'issues' with that previous meta-analysis by Zheng and colleagues  around what they did and did not seemingly include in their paper. A meta-analysis or systematic review is only as good as the number and quality of the studies it includes.
The strength of the Tonacci review is that it followed those PRISMA guidance - the Preferred Reporting Items for Systematic reviews and Meta-Analyses - and also that "Methods for study selection and inclusion criteria were specified in advance and documented in PROSPERO protocol #CRD42014012851." In other words, much like when study protocols for clinical trials are pre-registered to avoid any 'massaging' of results or changing/switching outcomes, so their aims and objectives were on record for all to see.
Where next for the suggestion of a possible link between asthma and autism? Well, how about taking into account a role for comorbidity as per the increasingly strong evidence coming out about how asthma and attention-deficit hyperactivity disorder (ADHD) may be linked (see here) and what that means for the over-representation of ADHD in autism or vice-versa (see here). I might once again suggest that immune function (i.e. inflammation or inflammatory processes) could be a common variable requiring further study too (see here for example). Such research may wish to take into account overlapping genetics/epigenetics as being important as well as the more functional biochemistry of immune system processes.
Given also the specific focus on "allergic asthma" by Tonacci et al I'm also wondering whether the various research on allergy symptoms affecting autism presentation might be important for some (see here). Indeed, with no medical advice given or intended, the idea of treating allergic disease in cases of ADHD for example (see here) is perhaps an area ripe for further investigation when it comes to autistic presentation too...
To close: Guardians of the Galaxy is back (and the soundtrack will be as cool as ever I guess).
 Tonacci A. et al. A systematic review of the association between allergic asthma and autism. Minerva Pediatr. 2016 Oct 5.
 Zheng Z. et al. Association between Asthma and Autism Spectrum Disorder: A Meta-Analysis. PLoS One. 2016 Jun 3;11(6):e0156662.
Tonacci A, Billeci L, Ruta L, Tartarisco G, Pioggia G, & Gangemi S (2016). A systematic review of the association between allergic asthma and autism. Minerva pediatrica PMID: 27706122