The Genetics of Attention Deficit Disorder

Posted: October 2, 2010 in Sociobiology

For years a debate has been going on about the cause of attention deficit hyperactivity disorder (ADHD).  The social scientists have been arguing that it was all about nurture while the real scientists, noting the tendency for the disorder to run in families argued for a genetic cause.  An important new study comes down heavily on the side of biology. (1)

One in 50 children are affected by the disorder, which attracts disapproving looks and frequent scolding from people convinced that the bad behavior is due to poor parenting, too much sugar or too many additives in the child’s diet.

Children with ADHD are impulsive and have an inability to focus, which causes difficulties at home and school, placing immense strain on their families. The burden has been aggravated by the stigma attached to the disorder which attributes responsibility to the parents.

Now scientists from Cardiff University in the UK, say the origin of the behavior is in the genes. They compared the DNA of two groups of children with and without ADHD and have discovered differences between them which provide the first direct evidence of a genetic cause.

In an interview with the BBC, Anita Thapar, professor of child and adolescent psychiatry at Cardiff University, said: “We are really excited by these findings. We have known ADHD runs in families but this is the first evidence of a direct genetic link. We hope these findings will help overcome the stigma associated with ADHD.

“Too often people dismiss it as being down to bad parenting or poor diet. As a clinician it was clear to me this was unlikely to be the case. Now we can say with confidence that ADHD is a genetic disease and that the brains of children with this condition develop differently to the brains of other children.”

ADHD is known to run in families – identical twins have a three-in-four chance of having the condition if their twin also has it. But, until now, debate has raged over whether the “heritability” of the condition was the result of a shared environment or shared genes.

The researchers analyzed the genomes of 366 children who had been diagnosed by doctors with ADHD and compared them with the genomes of 1,000 controls. They found that chunks of DNA which were either missing or duplicated were twice as common in the children with ADHD. The findings are published in The Lancet.

Professor Thapar said the parts of the genome affected were the same as those involved in autism and schizophrenia, suggesting a potential overlap between the conditions.

“It gives us a window into the biology of the brain. The findings will help unravel the biological basis of the condition and could help develop treatments.”

Treatment for ADHD is limited to alleviating the symptoms with drugs, behavioral management and school support. “It is palliative. It doesn’t cure but it takes the edge off the symptoms. The hope is that by better understanding the biology we can have more specific types of medication,” Professor Thapar said.

She added that there was no evidence that bad parenting or poor diet caused ADHD, although it could affect behavior in other children. “We have looked – but we have found none. To manage children with ADHD you need to be a super-parent to handle the difficulties. But that doesn’t mean the parenting caused the difficulties,” she said.

  1. 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
    DOI: 10.1016/S0140-6736(10)61109-9
  1. Ali says:

    I don’t think ADHD should be called a “disease” or “disorder” at all. Back when we were hunting and being hunted, ADHD was one of the best things you could have happen to you. You’d pick up on rustling in the bushes, cracked branches, etc. and it would lead to either a delicious antelope, or you not being dinner for some other animal.

    And, I think that a preponderance of people who we can classify as “successful” also have ADHD to some extent, and it has proved quite useful in starting profitable companies, useful inventions, and so on.

    The people who call it a “disease” or “disorder” are the worker bees. But, frankly, the world needs its worker bees.

  2. the HANman says:

    Chalk another one up to genetics!

  3. calistolite says:

    This is pretty cool but at the same time not too unexpected.

  4. Mary T says:

    Can’t believe that all that’s being done is taking the edge off the symptoms. This better get things rolling faster…

  5. Daniel says:

    adhd is just a word. each patients case is so highly subjective that i find the notion to apply a generalized label ludicrous arbritrary and irrelevant. even moreso to give some synthesized alledgedly magic pill

    • Don’t really know what your point is but you can say the same thing about every genetic disorder–it doesn’t make it any less genetic.

      • Daniel says:

        correct, everything is genetic – so you choose to take a few select, random characteristics and grant these a label? what makes these characteristics so special? this “disorder” you speak of is phony. you could take any group of characteristics, give them a label and find a bunch of people to whom this new “disorder” fits. then proceed to perscribe meds and $$$$$

      • Huh? These people have genetic abnormalities. It has nothing to do with characteristics, labels, or anything else. Nobody even mentioned meds. Read the report. There are genetic differences! That is all this is about,

      • Daniel says:

        the point i’m trying to push home here is that there is no such thing as adhd; thus any report done on it is worthless science (not to mention wasted funding)

  6. Sam Kim says:

    Hatem, the Lancet study you cited seems to be pretty compelling evidence that ADHD has a strong genetic component. Just look at the p-values in the statistical analysis section, and the overlap between CNVs associated with ADHD and genetic loci associated with schizophrenia and autism.

    I still have some issues with the methodology behind the study.

    ALL of the subjects in the experimental group came from one single Western nation, the United Kingdom. Granted, ADHD appears to be present in nearly all nations surveyed by psychologists, but its prevalence appears to differ strongly from country to country when the DSM IV’s own criteria are employed. See

    Furthermore, we still don’t know whether genetic differences between the control and experimental groups point to causation rather than mere correlation. I get the impression that standards employed throughout the social sciences to categorize people who display aberrant behaviors are inexact and sometimes arbitrary. What does it even mean for a child to have a “perfect diagnosis” for ADHD? What would be the SI units for hyperactivity and inattention?

  7. a_engr1948 says:

    I always like to see hard science triumph. Don’t know much about the subject but interesting, nonetheless.

  8. t_fish says:

    I just love it when science trumps fake “social science.”

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