The genetics of ADHD
October 11, 2010 There is a danger of reading too much into new research in the Lancet on attention-deficit hyperactivity disorder (ADHD). The headline of the Lancet press release says: "Study is the first to find direct evidence that ADHD is a genetic disorder". One of the authors, Professor Anita Thapar is quoted as saying: "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".
That's that then. Or perhaps not. Because those bold claims do not seem to be borne out by the actual research paper. The study analysed DNA from 366 children with ADHD and 1,047 controls. They found that those with ADHD were twice as likely to have chunks of DNA missing or duplicated, areas known as copy number variants. This genetic variation was also found to be more common in brain disorders.
I have done the sums and around 15% of the ADHD children had the genetic variant and about 7% of the control group did not. Put that another way, it affected one in seven of the ADHD group and one in 14 of those without.
That also means that seven out of eight of the ADHD group did not have the genetic variant - which hardly justifies Professor Thapar's confident assertion that ADHD is a genetic disease. I put this to Professor Thapar and she was keen to stress that she was not asserting that genes alone were responsible for ADHD but rather a complex mix of genes and environmental factors.
On the Today programme, the clinical psychologist Oliver James tore into the research and made accusations of "massive spin".
Professor Thapar said that ADHD could not be dismissed as being down to bad parenting or poor diet. She hoped the research would remove the stigma associated with the condition. The trouble with the Lancet press release is it appears to remove parenting and the environment from the equation; something which Professor Thapar told me was not her intention.
Professor Tim Kendall a consultant psychiatrist and a leading expert on ADHD, was also troubled by bold assertions which labelled the condition as genetic. He said there was a danger that giving a biological explanation to ADHD would encourage clinicians to rely on a biological answer, namely drugs like Ritalin. Just two years ago doctors were urged by NICE not to rely on Ritalin alone. Support and training for parents and teachers were flagged up as of key importance in helping children control the condition.
Professor Kendall also gave a long list of environmental factors which he said can increase the risk of ADHD: smoking during pregnancy, pre-natal stress, abuse during childhood, marital breakdown and poverty. He also pointed to twin studies and other research which suggested a genetic element to the condition.
Like many disorders, there is no simple cause behind ADHD. Simply blaming poor parenting is surely as bad as saying it's all down to our genes. Parents of children with ADHD would prefer help rather than labels.
