It’s not ADHD Sir, it’s in my genes….

Another headline (Daily Telegraph Friday 1^st October, 2010), another human genome versus disease study. And a very similar story to the genetics of myopia (see my previous post ill-communications.blogspot.com). Some serious science (published in The Lancet) looking at DNA variations in groups of individuals with a disease, in this case the psychological syndrome, attention deficit hyperactivity disorder. Some ill-advised press releases and comments: "Study is the first to find direct evidence that ADHD is a genetic disorder" (Lancet press release) and "Now we can say with confidence that ADHD is a genetic disease and that the brains of children with this condition develop differently to those of other children" (Prof Anita Thapar, the lead author of the Lancet paper). Lots of media hoo-haa. See the excellent blog by the BBC’s medical correspondent, Fergus Walsh,  for a summary of the main issues that got discussed.

Just like myopia, ADHD is a ‘complex’ condition caused by a whole variety of factors. These may include genetic risk factors but they also include environmental risk factors: smoking during pregnancy, pre-natal stress, and the usual social problems linked to child behavioural problems such as abuse, marital breakdown and poverty. And just like myopia, it appears that the environmental factors dwarf the genetic. In the Lancet paper, it is reported that 14% of children with ADHD had large variations in their DNA that were only present in 7% of children without ADHD. Or to put it another way, only 1 in every 7 children with ADHD had the genetic variant. Moreover, the particular type of genetic variation present, known as ‘copy number variations’ – deletions or duplications of large chunks of DNA  - do not resolve neatly down to this gene or that. In fact 57 different variations were found in the group of 366 children with ADHD. It is difficult to imagine, even in the science fiction world of routine genome tweaking, a treatment that will correct this.

So perhaps it is time the scientists got smart? As the debate about the amount of UK public money spent on scientific research reaches its zenith (see http://www.guardian.co.uk/science), is it really worth spending serious amounts of public money characterising the minute genetic risk factors of complex disorders like ADHD?