Genetics of ADHD

One of my readers forwarded this question: “what are the chances that I will pass ADHD on to my kids?”

This is a great question, which goes right to the heart of the genetics of ADD or ADHD.

As I explained in a previous article about the cause of ADHD, ADD and ADHD are very ‘heritable’, meaning that it is a very genetic disorder.

Many twin and family studies have been done on this topic. While each study yielded slightly different results, here is a summary:

If a person has ADHD, then:

  • an identical twin has a 78-92% chance of having ADHD as well.
  • 25-35% of siblings have ADHD as well.
  • 15-20% of the mothers have ADHD as well.
  • 25-30% of the fathers have ADHD as well.

If a parent has ADHD, there is a 20-54% chance that his/her child will get ADHD as well.

If both parents have ADHD – well, I don’t know of any research statistics, but let’s just say that there is a very high chance of a child having ADHD as well.

So, to answer the specific question – if you have ADHD, and you plan to have kids, each child has about a 20-54% chance of having ADD or ADHD.

Comments

  1. Hi,
    It seems when kids do inherit the ‘ ADHD genes ‘ , they get it far worse than we did. A friend of mine has this theory that when a gene mutates the defect becomes bigger. I wish this was true with our good genes.

    How do you explain this phenomenem

    Allan

  2. Allan – thank you for your comment.
    There is a genetic theory called ‘anticipation’.
    This refers to the fact that certain genetic disorders do worsen when they pass from one generation to the next.
    That said, I do not believe that ADHD has been described as displaying ‘genetic anticipation’. But if you want to read more, then this is the term to look for.
    In my clinical experience, I have seen ADHD getting worse when both parents have it, or if one parent has it, and the other has a family history of it.
    Thanks again for reading and commenting.
    Dr. Kenny

  3. Dear Dr Kenny
    I suspect that in the long run, ADHD will prove to be highly polygenic despite the tight focus on dopamine receptor and transporter genes. Recent work on the genetics of Bipolar Disorder and Schizophrenia by Pamela Sklar is pointing to more fundamental issues (both of these disorders have links to ADHD) .
    The work by Martin Pall on NO/ONO (nitric oxide/peroxynitrite) metabolic problems may also shed light.
    If ADHD is highly polygenic, and as several have asserted, that assortive mating is prevalent, then one would expect more double recessives to appear and traits to strengthen.

  4. So Calochilus what your saying is in theory the increased symptoms is not because the child is raised viewing these symptoms as a normality and thus increasing the symptoms the child displays in addition to his/her own add but merely because these genes stack to create stronger symptoms. From what I know in genetics(very limited) I see that most genes take the predominate feature of the two but to have these two combine is a different view that I have not considered yet. Are there studies that have focused on this specifically that are available to the public?

  5. Hi, none of that information has any direct genetic basis and could as easily a result of the environment. You’d need statistics on non-identical twins and adoption studies as well for that to have any relevance, ADD is just behaviourally inherited based on what you said

  6. Much behaviour is learned, not inherited.
    If you want statistics, see the work of Hay and Levy, enough there to keep you reading for some time. Overall conclusion, ADHD heritabilty is between 0.8 and 0.9
    See http://www.cognitivepsychologyarena.com/attention-genes-and-adhd-9781841692678
    The learned aspects are more related to oppositional defiance and conduct disorder according to Barkley.
    However, a complicating factor that is being more widely recognised is the impact of epigenetics.
    See http://www.epidna.com/showabstract.php?pmid=17915085
    also http://eprints.qut.edu.au/13794/ where epigenetics is explored in relation to PTSD. Martin Pall’s work has shown possible links in physiological mechanisms relating to this.
    See also http://www3.interscience.wiley.com/journal/120120678/abstract?CRETRY=1&SRETRY=0
    See also http://www.mdconsult.com/das/article/body/180511137-2/jorg=journal&source=&sp=N&sid=0/N/721514/1.html?issn=
    Happy reading

  7. Follow up question:

    My brother has ADHD (at the higher end of the scale) , my partner I do not, what is the chance of us having a child with ADHD?

    Thanks

    • Hi,
      If I understand correctly – you’re wondering what the risk of having ADHD in your child if your brother has ADHD. I don’t know an exact answer to that… The general population risk is 5%. With someone in the family – it would be up a little- but with an uncle – probably not that much.
      Dr. Kenny

  8. Hi Lizzie
    Your problems come about when trying to reconcile the DSM4 diagnostic criteria which are categorical (ie. you either have ADHD or you don’t), with the reality of ADHD which is a dimensional problem ( meaning that ADHD issues or traits can vary from immeasurable to devastating).
    Not only are ADHD issues dimensional, but there are several, more or less, independent domains such as attention, distractability, impulsivity, together with various comorbid (occurring at the same time) but possibly distinct issues such as dyspraxias, central auditory processing issues and visual processing issues (the dyslexias and Irlen Syndrome, etc). If you want to get a handle (no pun intended) on this stuff, you should read John Ratey and Catherine Johnson, “Shadow Syndromes”
    The reality is that DSM4 deals poorly with women with ADHD as the diagnostic statistics show. One in five children diagnosed with ADHD are girls. In adulthood, the ratio is one to one. This tells me that DSM4 is missing many girls with the ADHD traits which are of minimal impact in childhood but greater impact in adulthood. (Is this because girls have greater verbal skills which mature earlier than boys?)
    The other reality is that the small proportion of boys with severe behavioural issues have dominated stereotypes of ADHD. 80% of ADHD kids are remarkable by their invisibility to the bulk of the population, the daydreamers, the “Walter Mittys” of this world. The others who are not un-remarked but are un-acknowledged as ADHD are the artists, musicians, mathematicians, entrepreneurs, inventors etc. who have a strong risk-taking streak in an intellectual sense.
    Given that you have a brother with well defined ADHD, my suspicions are that you will have ADHD traits which are a minor impediment to your progress. I also firmly believe that assortative mating is common and the chances are (in my mind) that your boyfriend will also have minor ADHD traits (which may be complementary to yours)
    Jump in, take the plunge, your children might well include the next Albert Einstein or Pablo Picasso.

  9. My question is what is the chance that a person who has ADHD or ADD in their family who does not themselves have it yet they have two of four children who has the syndrome yet their husband does not have it nor is it carried in his family?. Would it be possible that they mated with another individual who has it?

    • Celeste, I can’t answer that… that’s a complicated problem.
      I would suggest that there is either someone in the family with ‘traits’, who never got diagnosed. Or, it could be de novo genetic changes. There is new research going on in ‘CNVs’ which are copy number variants. These are genetic changes that are bigger than what have been looked at in the past – i.e. 200-500 dna base pairs. For a certain percentage of people there are de novo mutations (i.e. there may be changes that aren’t in the family). That’s all I can say to help out.

  10. Interesting. Thanks for posting this. Both of My Husbands parents have ADD (and have been very successful, despite having it) so it was probably very inevitable for him. Interesting to see the percentages.

  11. What are the chances that ADHD will be passed on from genes inherited from a grandfather? In this case, the grandfather is diagnosed with ADHD. His daughter is not ADHD. What are the chances that this daughter would pass on ADHD to her child? Thank you.

  12. Hi there, my partner and I have been thinking about starting a family (im 27 his 21) but he has ADHD and I am very worried that our children would get this passed onto them? His dad also has it, not diagnosed but I know he has it I can tell! I looked on this website as I was a bit worried and then seeing links between adhd and Bipolar and it has scared the hell out of me as I found out last year my dad has bipolar!!! Please can someone tell me if this seems to be the case or if I should just stop scaring myself by reading comments, who could I speak to about this? Sorry for going on and thank you in advance for any advice! Thanks Stacey.

  13. Hello. My husband and I have been trying to conviece. He is worried about the chances of our child having ADD or ADHD.

    I am ADD- I was diagnosed in 2000, age 14, but was able to over come it and make a successful life for myself.

    My husband has ADHD and was diagnosed in 1990 at the age of 4. He has struggled with medication, which has been awful for him. He doesn’t remember much of his childhood and had a hard time socializing with people.

    Now we would like to start a family. What are the chances of a ADHD child with one parent is who ADD and one parent is ADHD?

    Thanks.

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