You may well have seen all the reports on TV that attention-deficit hyperactivity disorder (ADHD) is caused by a genetic difference. This follows a study conducted by Cardiff University published in The Lancet. The CNN piece is typical:
A new study in the Lancet provides the first direct evidence that genetic abnormalities are responsible for attention-deficit hyperactivity disorder, ADHD.
Except that the study shows nothing of sort. Indeed if anything it shows genetics are not the main cause of ADHD.
The public has again been the victim of the press's own ADHD - Anti-scientific Disinformation Hyperbole Disorder who cause is patently obvious - laziness and lack of professional journalism standards and knowledge.
Even worse in this case, it would appear to reinforce the justifications for what are considered inappropriate treatments in other countries and divert from addressing social/environmental factors in the USA that could well increase the incidence of ADHD.
The root of the problem with this story appears to be that most TV newsrooms read (or understood) little beyond the first four paragraphs of the Reuters report on the Lancet article (itself based on a Lancet press release). The Reuters wire is handily reproduced in full on the ABC News web site.
Their poor little minds clearly go numb when faced with figures or science so the AP wire written by their medical correspondent was apparently ignored and none went to the original Lancet page. Yet it sets out exactly why their breathless reporting of a direct genetic cause and the rest of their news items on the research was so wrong:
British researchers compared the genomes of 366 white British children from 5 to 17 years old with attention deficit hyperactivity, or ADHD, to those of more than 1,000 similar children without the disorder. The scientists focused on a sequence of genes linked to brain development that has previously been connected to conditions like autism and schizophrenia.
In children without ADHD, about 7 percent of them had deleted or doubled chromosomes in the analyzed gene sequence. But among children with the disorder, researchers discovered about 14 percent had such genetic alterations. Scientists also found that 36 percent of children with learning disabilities in the study had the chromosomal abnormalities.
(Going back to the data in the original Lancet page) 57 of the 366 children diagnosed with ADHD, or 15.56%, had the chromosome differences looked for whereas of the 1047 in the control group 78 or 7.45% showed them. The researchers set out this as the basis for their study.
Large, rare chromosomal deletions and duplications known as copy number variants (CNVs) have been implicated in neurodevelopmental disorders similar to attention-deficit hyperactivity disorder (ADHD). We aimed to establish whether burden of CNVs was increased in ADHD, and to investigate whether identified CNVs were enriched for loci previously identified in autism and schizophrenia.
So their research showed that 15.6% of children diagnosed with ADHD had the same chromosome variations previously identified in those with autism and schizophrenia. But it therefore also showed that 84.4% did not.
As an aside, surely another interpretation of their data could be that ADHD does not have this chromosomal cause or contribution. Given that, the study could be showing that a number of children with autism spectrum disorders or schizophrenia have been wrongly diagnosed as having ADHD. Had they had set out to demonstrate a hypothesis that there is no such link between ADHD and the other conditions, they may have investigated the "positive" group further.
While the US networks were busy getting quotes from doctors and parents based on the initial and incomplete versions they presented them with, the BBC's medical correspondent, Fergus Walsh, was apparently doing some further work and the statistical problems were far more widely reported and the chromosome evidence put in better context during BBC programs:
(Fergus Walsh) put this to Professor Thapar (one of the authors) 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.
Fergus Walsh's blog on the BBC site.
So clearly the authors would disagree with the early reports of there being a single genetic cause for ADHD and the BBC went on to point out the dangers of relying on this to inform treatments:
Professor Tim Kendall, a director of the National Collaborating Centre for Mental Health, said a number of factors caused ADHD and blaming it purely on genetics could mean incorrect treatments.
"I'm pretty sure these studies are not going to produce undoubtable evidence that ADHD is caused solely genetically.
"I am saying it's a mixture of genetic and environmental factors, and the important thing is that we don't end up thinking this is a biological problem which is only subject to biological treatments like Ritalin."
As Walsh points out, the UK's National Institute of Health and Clinical Excellence (NICE) recommends doctors not to rely on Ritalin alone but cites support and training for parents and teachers "as of key importance in helping children control the condition."
This different approach also points to another problem with investigating ADHD. Different countries use different diagnostic criteria which means it is almost impossible to compare incidence levels. There does appear to be a higher number diagnosed in the USA than in other countries. It is also generally accepted to be related to a number of factors but there are two that might be contributing to this apparently higher incidence in the USA. They are the level of stress hormones in the womb and the immediate post-natal period of building relations between mother and child.
It has been recently pointed out in another diary here that the USA has the poorest benefits for women during the peri-natal period in the West. Working American women have the lowest amount of time off and the least security of post when they return. Of course there are also questions of access to and cost of health care during this period.
So it seems logical that these both cause stress in late pregnancy and make it more difficult for working Americans to fully develop an early bond between themselves and their baby. Surely if this link between lower benefits and higher incidence of ADHD in later childhood were established, it would provide powerful evidence to improve the lot of working American women.