ADHD is a genetic disorder, sort of. The human microbiome is very big now. Climate change in Washington and elsewhere.
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ATTENTION DEFICIT HYPOACTIVITY. Huge news — but of a kind that confounds rather than clarifies. Which may account for the relative lack of trumpeting-from-the-rooftops sort of reception that would normally be accorded a Lancet-annointed study complete with widely available press conference and much potential impact. Unclarity plus the fact that, for all their novelty and import, the findings have been oversold by both the journal and the researchers.
The basic finding was this: children with attention-deficit hyperactivity disorder (ADHD) are more likely to have copy number variants — large stretches of DNA either duplicated or missing — than controls. Ewen Callaway describes the study at The Great Beyond and so does Andy Coghlan at New Scientist Health. Lancet abstract here.
Copy number variation (aka CNV) is an intriguing phenomenon. Copy number variants are not SNPs (single-nucleotide polymorphisms), but larger stretches of DNA, and they are very, very common. CNVs may be one reason each of us is unique. They may account for "penetrance": why genetic diseases don't always manifest themselves, or don't manifest themselves severely, in some people who possess the disease gene. CNVs may affect disease susceptibility and drug reactions.
They also have been associated with several diseases, especially some affecting the brain. So it's not astonishing that they have now been found in a significant number of ADHD sufferers. The press release (and some stories) quoted senior author Anita Thapar, a child psychiatrist at Cardiff University in the UK, declaring flatly, "Now we can say with confidence that ADHD is a genetic disease ..."
You and I know from hard experience that such a comment does not necessarily mean that ADHD is a genetic disease full stop, no other explanations need apply. But I bet most folks will read it literally, and the takeaway will be exactly that: ADHD is a genetic disease full stop, no other explanations need apply. A distressing failure of communication.
Some stories noted that CNV was twice as common in the ADHD group as in controls. That's quite true, and sounds impressive. But the actual numbers tell a different story. CNVs were found in only 57 of 366 ADHD kids, 15.6%. They were also found in 78 of 1047 controls, 7.5%. Yes, that does suggest that CNVs may figure in some cases of ADHD. Given the increasing frequency of that diagnosis, a mere 15.6% could still translate into very large numbers of kids.
OTOH, the percentage of CNVs among controls is not negligible either. Which is not weird, considering that CNVs are pretty common in the "normal" population and researchers have only vague notions what they might be up to, if anything. (BTW, the controls in this study were not, as you might expect, non-ADHD kids. They were drawn from an unselected group of people born in 1958. Leaving it to statisticians to explain why that's perfectly okay, I will hurry right along.)
Skeptics I have found only on blogs, and not many of them. But it's early days yet; the embargo was up only Wednesday evening. At The Guardian, Johnjoe McFadden is doubtful. At Fergus's Medical Files at the BBC, Fergus Walsh does the math and is doubtful too. Not much interest so far in the US, which is odd considering how hot a topic ADHD is here. Couldn't be because it's a Brit study in a Brit journal, could it? Nah.
I'm peeved at the paper's flamboyant presentation, which was misleading about the findings. But to my mind it makes a convincing case for likely CNV involvement in at least some ADHD. The data are particularly noteworthy for kids with IQs <70. There were only 14 of them with CNVs, but that was 42% of the n = 33.
Senior author Thapar has been quoted as expressing satisfaction that establishing ADHD as a genetic disorder means that it will no longer be blamed (unjustifiably) on bad parenting. I applaud this compassion and social sensitivity, and suspect it played a role in the (unjustifiable) hyperactivity surrounding this paper.
But the fact is that the data don't get parents off the hook. There's still a lot of room to blame bad parenting. ADHD has been attributed to zillions of other causes too — diet, heavy metals, and for all I know witchcraft. This paper gets none of those suspects off the hook either. CNVs may be shown eventually to figure in more than 1.6 cases of ADHD out of 10, but it's pretty unlikely that they will ever be the whole story.
IT'S A SMALL WORLD AFTER ALL. It's been a hectic and distracted week here in the Woebegone Desert, and as a result you are getting short shrift from me. So just a bit more food for thought, (mostly) sans commentary:
One of my favorite mind-boggling factlets is this: 9 out of 10 of your body cells are not "you" at all. They belong to microbes, and you couldn't exist without them. Cherish your bugs. And catch up with the recent Human Microbiome Research Conference at Tree of Life, run by evolutionary biologist Jonathan Eisen. A personal and professional log, and lots of links to other sources.
ALL CLIMATE IS LOCAL, AND CLIMATE CHANGE MITIGATION IS LOCAL TOO. Even if we got serious about fixing climate change tomorrow, we'd still be coping with our past negligence for decades to come. On Wednesday the White House was given a report outlining how, as Eli Kintisch puts it at ScienceInsider, "The federal government is way behind on efforts to develop effective strategies to adapt to a changing climate ..." The report is not about possible future changing climate, it's about the changing climate that is upon us now.
At the Great Beyond, Jeff Tollefson summarizes the report thus:
The gist is that the United States needs to integrate federal climate programmes, collect and disseminate data and facilitate coordination with both regional governments and the private sector. The report recommends boosting funding for research into climate impacts and creating a federal "portal" for climate data as well as a clearinghouse for information about adaptation programmes underway at all levels of government and industry.
Some cities — Chicago, for instance — have begun to cope already. Michael J. Coren has a long post at the Yale Forum on Climate Change and the Media describing what cities and other localities are doing, even if the federal government isn't.
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