By Paul Rincon
BBC News Online science staff, at the BA festival
Parents of children with attention deficit hyperactive disorder (ADHD) often show signs of the condition themselves, research has suggested.
The brains of children with ADHD are different, say researchers
University of Wales at Bangor scientists said this made dealing with their child's condition more difficult.
But they told the British Association Festival of Science in Exeter that sharing these symptoms did not put the child at any greater risk.
Nor did it mean ADHD adults necessarily had poor parenting skills, they argued.
Children with ADHD have extreme difficulty sitting still, learning or concentrating; and looking after these children can be exhausting for parents.
Dr David Daley, from Bangor's School of Psychology who led the research, said: "Parenting a child with ADHD when you have symptoms yourself must be the most difficult thing to do."
However, he said his study of over 250 parents and children indicated there might be some positive aspects to sharing ADHD traits between parent and child.
The research confirms that in families with shared symptoms, ADHD parents are more likely to engage in negative and undesirable parenting practices, and have a negative emotional relationship with their child.
But this group of parents is also more likely to engage in affectionate and constructive parenting when dealing with their child.
This includes the parent expanding on a child's play idea, without criticism, and spending more time playing together, all of which are positive parenting traits.
The conference also heard further evidence of the genetic basis for the condition.
Professor Eric Taylor of the Institute of Psychiatry said the disorder had a genetic component of around 80%, but that ADHD was not caused by one gene, but by the cumulative effect of several, which had small effects.
He said scans showed real differences in the brains of children with the condition.
Magnetic Resonance Imaging (MRI) scans found they tended to have smaller right frontal lobes, a small vermis (a feature of the brain region known as the cerebellum) and some regions of the basal ganglia are also smaller.
Professor Taylor said: "Those parts of the brain that are under-active are those that we use for stopping ourselves, for holding ourselves back."
He said only a third of children with the severe form of the disorder were receiving medication.
Researchers from the institute followed children from the age of seven who displayed hyperactive behaviour but had not been diagnosed with a disorder.
They then followed them until they were aged 17.
It was found that those children had a four-fold increase in the likelihood of developing a mental disorder.
About 250,000 in children in Britain are believed to have ADHD. Some 80,000 have the more severe form of the disorder.