Attention-deficit hyperactivity disporder (ADHD) is a genetic disease, say today’s headlines. Is it?
 
What a new study reported in all the papers actually shows is the existence of a genetic variant that may help explain a familial link that has long been known to exist. Parents with ADHD are more likely to have children with ADHD. So clearly there’s a genetic influence at work: that’s not news.
 
The results reported in The Lancet from a team in Cardiff show that a particular genetic variant is about twice as likely to be found in the brains of those with ADHD as in unaffected controls.
 
But it does not show that all cases of ADHD are caused by this variant, nor that carrying it condemns a child to the condition: only 14 per cent of the cases carried it. And 7 per cent of “normal” controls (people never diagnosed with ADHD) also carry it without apparent ill-effects.

             How The Times headlined the story:

          
 
These findings are interesting but poorly reported - yet another example of how easy it is to overstate findings where risks are involved. Here the relative risk is about 2 (14 per cent vs 7 per cent) or rather lower if only children of normal intelligence are considered (1.68).
 
If the absolute risk of ADHD is 20 in 1000, as the authors of the paper suggest, then the absolute risk among those of normal intelligence who carry the variants is 34 per 1000. That sounds a lot less alarming and possibly a lot less interesting.
 
Other genetic variants may be found that account for other cases. But it is clear that carrying this particular variant does not condemn a child to ADHD, nor does it mean that psychological therapies, better teaching, or better parenting are powerless to help.
 
The authors claim that their finding has removed the “stigma” from ADHD. But genetic determinism is just as dangerous as stigmatisation, and just as likely to lead to despair.  Some ground rules for reporting this kind of study are urgently needed.