A recent study led by Professor Anita Thapar and funded by the Wellcome Trust has found an increased number of 'copy number variants' (CNVs) in the genomes of children diagnosed with ADHD. (CNVs occur when there are bits of DNA which are either duplicated or missing.) Similar CNVs are also found in those with autism and schizophrenia.

However, there is some controversy over how significant these findings actually are. The study analysed 366 children with ADHD and 1,047 controls. One in seven of the ADHD children were found to have the variants, one in 14 of the control children had them. This is not a great number.

The study is being 'hyped' as 'ADHD down to genes not to poor parenting' but the facts scarcely support this. Other ADHD experts and commentators are suggesting that it merely reinforces the already accepted notion that ADHD children may have a genetic predisposition to the condition but that there are many other factors which need to be present for the child to actually suffer from the condition. They are also warning that this research should not be used to encourage treatment with drugs as opposed to other environmental and psychiatric interventions.

For helpful comments see BBC medical correspondent Fergus Walsh's blog and, for the dietary angle, Michelle's blog.

Rare chromosomal deletions and duplications in attention-deficit hyperactivity disorder: a genome-wide analysis. The Lancet, Early Online Publication, 30 September 2010

First published in September 2010

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