CNVs are sections of the genome in which there are variations from the usual 2 copies of each chromosome, such that some individuals will carry just 1 (a deletion) and others will have 3 or more (duplications).
Of course, even if the presence of CNV's were serious proof that ADHD is invariably a genetic disorder - and it is not for reasons I will mention shortly - this would mean that a whopping eighty five percent of kids diagnosed with ADHD did not have the disorder! That is one hell of a rate of misdiagnosis.
The presence of CNV's do not prove genetic origins for most cases of ADHD at all, although they may quite possibly predispose some individuals to develop deficits in the neural networks of their brains. As you can see from the above data, 7% of normal kids have them.
Second, a high percentage of the kids diagnosed with ADHD who did have increased rates of CNVs also exhibited learning disabilities. In ancient times when I was in training, problems with attention were thought to be a side effect of learning disabilites such as dyslexia.
Last, the presence of higher numbers of CNV's in the regions of chromosomes the study authors found them in is not specific to ADHD, but is also seen in autism and schizophrenia.
This study should win the Oscar for Most Highly Exaggerated Claims of Significance of Data in a Research Study. Shame on the press for going along with the ruse.