"This current systematic review provides strong evidence that ADHD [attention-deficit hyperactivity disorder] is associated with atopic diseases and that individuals have a 30% to 50% greater chance of developing ADHD compared to controls."
So said the results of the systematic review and meta-analysis published by Jurjen van der Schans and colleagues  looking at the collected peer-reviewed science literature on how conditions such as asthma, eczema and rhinitis might increase the risk of a subsequent diagnosis of ADHD.
New news? Not to this blog it isn't (see here for example) as the Schans data really just adds the 'cherry on top' to the idea that such somatic conditions might *connect to* behavioural and/or developmental diagnoses. Preferential screening is of course implied but then also comes the million dollar question: what are the biological mechanisms linking atopy to something like ADHD? The answer is likely to be complex - immune system complex for example - but I might suggest that some starting clues may be found in some of the [limited] peer-reviewed literature talking about what happens to ADHD signs and symptoms for some when treatment for atopic disease is initiated (see here).
 van der Schans J. et al. Association of atopic diseases and attention-deficit/hyperactivity disorder: A systematic review and meta-analyses. Neurosci Biobehav Rev. 2017 Jan 19. pii: S0149-7634(16)30359-1.
Schans JV, Çiçek R, de Vries TW, Hak E, & Hoekstra PJ (2017). Association of atopic diseases and attention-deficit/hyperactivity disorder: A systematic review and meta-analyses. Neuroscience and biobehavioral reviews PMID: 28111269