|Light it up @ Wikipedia|
It should be noted that the Arns paper appears in a pretty good journal (Biological Psychiatry) so whilst you might be thinking, 'solar intensity... eh?' this is a correlation which has passed what one would expect to have been quite a rigorous peer-review battlefield. I could at this point offer you some more detailed description of the paper but it seems that the authors have already done that on their website (see here - no endorsement given or intended).
In effect, they mapped the prevalence figures for ADHD across various parts of the US and beyond and cross-referenced them with official figures relating to SI. Yes, prevalence of ADHD were partly based on "self-report of professional diagnoses" but this was to some degree countered by the use of more formal assessment data in other sites. They found a correlation (negative correlation) between ADHD prevalence and SI when controlling for various potential confounders: "a lower prevalence of ADHD in areas with high SI for both U.S. and non-U.S. data".
Bearing in mind the issue of correlation/causation (see here), one could construe this data several ways. If for example you work for the tourist boards of Arizona, Nevada or California you have a potentially interesting advert: 'Come live here, we've got lots of solar resource and potentially less risk of your children developing ADHD'. Or words to that effect. And indeed, the CDC figures do seem to suggest that those high SI states might have a lower prevalence of ADHD (assuming that this doesn't reflect other issues such as awareness, identification, etc). On a more serious note are the suggestions that (a) ADHD might be related to circadian clock disturbances, and (b) that exposure to the various new-fangled technologies we are surrounded by might be part and parcel of those circadian clock disturbances.
Just before you reach for the click away button, like I almost did, mumbling 'blame it all on technology', there are a few papers to bring to your attention. Yes, sleep issues are associated with ADHD** and indeed if the recent paper from Blesch and Breese McCoy*** is anything to go by, we might also assume that ADHD - some cases of ADHD - could be mistaken for things like sleep apnoea. True also that issues with circadian function seem also to be tied into cases of ADHD as per studies like this one from Gamble and colleagues****. On balance, sleep seems to show some connection with ADHD.
That the part of the light spectrum labelled blue emanating from various technology use is the primary cause or significant contributor to the sleep issues noted even in some cases of ADHD is the slightly more difficult proposition for me to whole-heartedly (hoof hearted!) accept from this work. I don't doubt that many children and adults with ADHD use this kind of technology. But I have to ask whether their use and exposure to the artificial blue light is really any more significant than that of everyone else? Indeed, without being an expert on the different ranges or wavelengths of light and their physiological effects, are we just talking blue or are we talking other parts of the light spectrum too?
There are details from this study which I would like to see further explored given the potential for a relationship between SI and ADHD prevalence. Readers for example, might know that I am more than a little intrigued by another sun related variable, vitamin D, and its various connections (or not) to conditions like autism or chronic fatigue syndrome among others. The question would have to be whether the sunshine vitamin / steroid hormone might also show some relationship to the latest findings? Are vitamin D levels likely to be greater / the same / reduced in cases of ADHD dependent on the specific geography and SI? Vitamin D receptors all in good working order*****? No significant drug interactions where medication is being used? Indeed, whether other correlates such as altitude - which also seem to map onto the SI exposure plots - might come into play?
There are questions which require some follow-up from this work but for now, and with all caveats in good working order when it comes to population studies of association - as with other recent results too, I'm intrigued by the Arns data and the suggested overlap. And also that ADHD might not be the only condition being looked at with a sun-related variable (see this study by Davis & Lowell******, full-text).
To close, after recently watching the quite brilliant film 'Rock of Ages' which satisfied all my 1980s rock needs, a taste of Sheffield's finest.
* Arns M. et al. Geographic Variation in the Prevalence of Attention-Deficit/Hyperactivity Disorder: The Sunny Perspective. Biol Psychiatry. March 2013.
** Yürümez E. & Kiliç BG. Relationship Between Sleep Problems and Quality of Life in Children With ADHD. J Atten Disord. March 2013.
*** Blesch L. & Breese McCoy SJ. Obstructive Sleep Apnea Mimics Attention Deficit Disorder. J Atten Disord. March 2013.
**** Gamble KL. et al. Delayed Sleep Timing and Symptoms in Adults With Attention-Deficit/Hyperactivity Disorder: A Controlled Actigraphy Study. Chronobiol Int. February 2013.
***** Malik S. et al. Common variants of the vitamin D binding protein gene and adverse health outcomes. Crit Rev Clin Lab Sci. 2013; 50: 1-22.
****** Davis GE. & Lowell WE. Variation in ultraviolet radiation and diabetes: evidence of an epigenetic effect that modulates diabetics' lifespan. Clinical Epigenetics. 2013; 5: 5.
Arns M, van der Heijden KB, Arnold LE, & Kenemans JL (2013). Geographic Variation in the Prevalence of Attention-Deficit/Hyperactivity Disorder: The Sunny Perspective. Biological psychiatry PMID: 23523340