View Full Version : The ADHD phenotype

04-22-13, 06:10 PM
Unfortunately, much of the research on this is new enough that it's hard to find links to full-text articles. Baby steps.

Characterizing the ADHD Phenotype for genetic studies ( goes back to 2005, but has some good background information about the basis for establishing a phenotype, and some of the research that created the standards.

Attention deficit/hyperactivity disorder (ADHD): Complex phenotype, simple genotype? ( is from 2004, and combines information that justifies the search for a phenotype along with a lot of information about confounding factors in compiling information from different research sources.

Neurobiology of Attention Deficit/Hyperactivity Disorder ( is newer, but as a meta-analysis, serves to provide more source information than robust data. Lots of links, but most of them will be to abstracts only. I include it mostly to show the wide variety of approaches that are being used that support ADHD as a valid phenotype rather than simply a diagnosis based on symptoms.

Happy reading!

04-22-13, 06:37 PM
A newer review paper:

04-22-13, 07:23 PM
Thank you! Meta-analyses, for me, tend to be more fun than a search engine. It's always nice to check the cited papers to see what's interesting (and compare the quality of the sources side by side sometimes!)

04-22-13, 07:51 PM
I'm going to have to keep this bookmarked. My interest was piqued by the studies suggesting a marker for adult ADHD that was shared by substance abuse. . .

04-22-13, 08:03 PM
I'm going to have to keep this bookmarked. My interest was piqued by the studies suggesting a marker for adult ADHD that was shared by substance abuse. . .

As someone with personal experience, I am also curious.

04-23-13, 03:12 PM
Sorry I'm going a bit off can just skip this paragraph and scroll to the link to avoid my tangential thought processes. I was thinking about sociopaths/psychopaths and how some studies have shown certain traits -like late bed wetting behaviors in males and fire starting. That got me thinking about inhibitory control -which made me think about ADHD and the decreased inhibition. So the bed wetting example got me thinking..maybe theres a link between other night time behaviors such as sleep talking/sleep movements(you can stick bruxism there as well) and ADHD? So I just did a cursory search and this was the first paper I looked at.

I know that my dad and I are notorious sleep talkers -but I'm the only one who grinds his teeth at night (really really badly...I chomp through nightguards fast!)
This could all just be coincidence....but it would be interesting if there were any other papers showing this relationship. Sorry...that was my random thought process of the day -hope you're all having a great day! :)

04-23-13, 07:40 PM
It actually is relevant, IMO, because if you look at the Mitchell article, it mentions psychosis as an emergent disorder that's genetically related. Both articles should get you thinking about how these shared symptoms can support genetic origins as long as you discard the outmoded thinking of genetic determinism.

You have clusters of genes that are found in multiple disorders, as well as points at which there are shared symptoms among the disorders. At some point in life, one of the mutations in copied cells keeps the shared symptoms and adds some others (or drops a couple, I'd say in some cases) and you end up with different maladaptions.

There are ages of onset for a lot of neurological and psychiatric conditions, but even with several late-onset diagnoses, symptoms and signals can be observed before the condition becomes full-formed. So determining the genetic indicators of risk is only one step towards narrowing down what the end result risk is actually going to be.

If that's the case, then people with early-onset disorders are actually more fortunate, because diagnosis and therapeutic interventions can start sooner. If you show no symptoms of mental or neurological problems until young adulthood, you've had no time to prepare to adapt.

04-23-13, 07:49 PM
BTW, there are much better sleep studies out there linking ADHD with sleep disturbances. They're bigger and newer, but in the end they say pretty much the same thing. :)

04-23-13, 08:47 PM
The epigenetic state of an organism (or “epigenome”) incorporates a landscape of complex and plastic molecular events that may underlie the missing link that integrates genotype with phenotype [54]. Through DNA methylation, histone modifications, and small regulatory RNAs, the epigenome systematically controls gene expression during development, both in utero and throughout life. Animal model studies have demonstrated that induction and stability of induced changes in the phenotype of the offspring involve altered epigenetic regulation by DNA methylation and covalent modifications of histones. In turn, opportunities arise for the induction of differential risk of non-communicable diseases in humans by variation in the quality of the early life environment.

04-23-13, 10:59 PM
BTW, there are much better sleep studies out there linking ADHD with sleep disturbances. They're bigger and newer, but in the end they say pretty much the same thing. :)

Interesting! Any links to the sleep abstracts?(I have access to most articles) I'm really curious now as to how strong the relationship is. I have another medical condition (Ehlers Danlos) which I thought might have explained the bruxism -but this may be just as relevant. I wonder if the studies showed decreased bruxism or sleep talking with stimulant meds...

I skimmed the lancet paper you mentioned a week ago or so. I agree -there
must be variable overlap between many of the different disorders and receptors. Interesting paper :)

04-24-13, 03:07 PM
Hubby just pointed out to me that I've been on here for 2 1/2 hours, so I'll open up a tab to remind myself later. I might also have a couple of links in a Word document, so I'll get back to you on that.

04-24-13, 03:21 PM
Heres a witty gene blog (perhaps its someone on this forum?)
Its breaks up the monotony of reading research papers :)

04-24-13, 07:48 PM
Which I haven't done because I went out shopping for about a half hour and then had to lie down for three to make my head stop exploding. Sorry. I still have the tab open. I feel so much better and get all excited and then my head reminds me that it just had surgery less than three weeks ago and takes revenge upon me. . .

However, I found a meta-analysis with free full text that might cite some decent research here (

04-27-13, 05:32 PM
I also need to investigate the links and some of the source material from this article (, as well, but I think it explains what many of us have been trying to get across, but maybe more concisely and clearly. From the conclusion:

And in contrast to the view championed by social constructionists – that understanding the biology ( of mental distress disregards personal experience – these discoveries imply that it needs to be front and centre, both in scientific studies and when working to help individuals. The mistake made by both sides was to consider biology and lived experience as somehow in opposition when really they are all part of our common humanity.

In other words, yes genes plus environment. But genes first. Environment acts on genetic expression, but doesn't change the genes that made us in the first place.