Genetics of ADHD
ByOne 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.
6 Comments
February 26th, 2007 at 2:58 am
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
February 26th, 2007 at 9:58 am
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
August 26th, 2008 at 10:39 pm
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.
April 19th, 2009 at 5:12 pm
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?
January 27th, 2010 at 10:15 am
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
January 28th, 2010 at 7:24 am
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