The researchers looked at 366 children with ADHD and 1,156 unrelated adults and found that the children with ADHD were far more likely to have large, rare Copy number variants (CNVs) than the adult control group. About 15% of the children with ADHD had one of these CNVs while only about 7% of the control group. Based on this finding, the the researchers are suggesting that ADHD is a "genetic disease and that the brains of children with this condition develop differently to those of other children"
Although it is not completely clear in the abstract, I think that the CNVs found were mostly unique in each child, although there might have been several children in the ADHD that had a duplication on 16p13.11. And yet, these mostly unique mutations are thought to help cause ADHD.
The similarities between this finding and what has been found in children with autism are striking.
These large, rare CNVs have been found to be more common in children with autism than the typical population. But more than that, children with autism also show many different CNVs with very little overlap. It is like each child has an almost unique mutation but yet these mutations are taken to have caused or contributed to the underlying disorder. And, at least in children with autism, most of the time these mutations are not inherited from the parents but rather are "de novo" (i.e random) mutations.
The similarities between ADHD and autism don't end there -
- Both conditions have historically been blamed on bad parenting.
- Both conditions are more common in boys than girls.
- Both conditions have become significantly more common over the past 30 years but the cause of the increase or whether there has been an actual increase is disputed.
- Both conditions are more common in some areas than others.
- Both conditions involve difficulties with social situations.
- Both conditions involve difficulties in being able to focus or pay attention to the outside world.
Anyone want to make a bet that ADHD and autism will be found to have similar causes?
Rare chromosomal deletions and duplications in attention-deficit hyperactivity disorder: a genome-wide analysis
Dr Nigel M Williams PhD,Irina Zaharieva BSc,Andrew Martin BSc,Kate Langley PhD,Kiran Mantripragada PhD,Ragnheidur Fossdal PhD,Hreinn Stefansson PhD,Kari Stefansson MD,Pall Magnusson MD,Olafur O Gudmundsson MD,Omar Gustafsson PhD,Prof Peter Holmans PhD,Prof Michael J Owen MD,Prof Michael O'Donovan MD,Prof Anita Thapar MD
The Lancet - 30 September 2010