DNA link to ADHD

2010-09-30 11:25

London - Children with attention deficit hyperactivity disorder are twice as likely to have missing or extra chromosomes than normal children - the first evidence that the disorder is genetic, a new study says.

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% of them had deleted or doubled chromosomes in the analysed gene sequence. But among children with the disorder, researchers discovered about 14% had such genetic alterations.

Scientists also found that 36% of children with learning disabilities in the study had the chromosomal abnormalities, compared to those with a normal IQ.


"This is the first time we've found that children with ADHD have chunks of DNA that are either duplicated or missing," said Anita Thapar, a professor at the MRC Centre in Neuropsychiatric Genetics and Genomics at Cardiff University who was one of the study's authors.

She said the findings are too early to affect diagnosis or treatment and are only applicable to people of European Caucasian descent because studies have not been done yet on other ethnicities.

The condition is estimated to affect millions of children around the world, and scientists have long thought the disorder has a genetic component.

US experts estimate that ADHD affects from 3% to 5% of school-age children in the US. There are no figures for developing nations.

The study was paid for by Action Research, Baily Thomas Charitable Trust, the Wellcome Trust, Britain's Medical Research Council and the EU. It was published online on Wednesday in the medical journal Lancet.

Peter Burbach, a professor of molecular neuroscience at University Medical Centre Utrecht in the Netherlands, was surprised some of the genetic defects found for ADHD were identical to ones for autism and schizophrenia. He was not connected to the Lancet research.

"There's a great chance the environment is modifying these genes," Burbach said, adding the genes could lead to several brain disorders, depending on things like the child's upbringing and other genetic factors.


He also thought scientists might eventually be able to reverse ADHD.

"This is not a structural abnormality in the brain, it's just the last phase of development that's gone wrong," he said. "It could be the brain just needs to be fine-tuned."

Philip Asherson, a professor of molecular psychiatry at the Institute of Psychiatry at King's College London, said the study only dealt with a subset of people with ADHD and said the environment should still be considered a cause.

In the case of some Romanian orphans, Asherson said there was proof that severe deprivation at an early age can lead to ADHD or other neurological problems.

Asherson said the medical world was still years away from being able to correct ADHD.

"The study doesn't tell us a lot about what's going on in the brains of people with ADHD," he said. "If we can find out more about these genes and how they affect brain development, that may give us inroads, but it's hard to say when that will be."

  • curious - 2010-09-30 11:46

    Does this mean that Einstein had a lower IQ, since he was diagnosed with ADD and autism?

  • Gonzo - 2010-09-30 15:05

    DNA=EVOLUTION, any creationist out there???

  • Luke - 2010-09-30 15:12

    I suffer from ADD and this was far to look at that bird

  • chromosomes? - 2010-09-30 19:04

    I really wish you guys would actually look up what certain words mean before publishing... Chromosome abnormalities are very rare and serious. For intance, if I had one extra copy of chromosome 21 (one of the smaller chromosomes) I would have down syndrome, not adhd... I'm pretty sure that what the original article meant (i admit to not having read it) was that certain sections of chromosomal dna (different to mitochondrial dna) were duplicated or missing. A far more subtle and likely explanation.

  • mandi moo - 2010-09-30 20:05

    A 'new study' says that ADHD is genetic - we know it's genetic, duh! What bright spark wrote this article?? It is negative and badly written, do some proper research, please.

  • you know... - 2010-10-01 07:37

    ADHD is a lot of bull! Stop giving children energy drinks, caffeine, apple juice, chocolate cereals, lack of exercise, no discipline.
    Breakfast is a chocolate cereal.
    School lunch is a sugar filled drink (no water)a chocolate sweet, chocolate muffin, bread with a jam spread. A few pieces of sugar coated dried fruit.
    Tuck shop money, child buys pink sweet, fudge, chips with loads of spices and a red lolly. Lunch is chicken nuggets and a sugary sauce a fizzy drink.
    Afternoon more cool drink because he/she is now dehydrated from all the extra hidden salts. Dinner is roast chicken baked in a sauce roast potatoes a few vegetables that get moved around there plates because they are so full of junk but they must eat whats on their plates. (parents don't see what their children are eating because they are to busy working and putting in extra time to buy more luxuries and to go on holidays with more empty harmful calories.
    And YOU know this it true!!!!!!

  • Ifrit - 2010-10-01 08:06

    No, in fact, people with ADHD are usually above the norm with reference to IQ, ADHD is irrelevant to IQ... Remember it's about ATTENTION... Not intelligence!

  • Michele Pearce - 2010-10-04 11:52

    @ you know. A few years ago I would have agreed with you.. EXPERIENCE proves you wrong. I'm a stay-at-home mom (not too busy to be involved with my childs diet, discipline etc), have a very structured and loving home, have 4 kids (all raised in exact same circumstances etc) and have only 1 of my 4 kids battling through with ADHD. Interestingly he is my only child who has NEVER (and I mean never) drank anything other than water - doesn't like any colddrinks etc - eats fruit, always has breakfast - usually a high-fibre bran with plain yoghurt etc and isn't a huge fan of sweets etc... ADHD IS real and ISN'T entirely diet related.

  • @you know... - 2010-10-06 10:32

    Perhaps you should do your research before commenting. I would agree that kids are too easily medicated for the plain and simple fact that it is the easy way out, HOWEVER, if you have ever dealth with an ADHD child you would very sweetly eat your own words. There are real cases of ADHD kids - not sugar induced. Some of them can't even have coloured meds. Careful what you write if you haven't done your homework!

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