Post by Amtram on Apr 24, 2014 9:34:34 GMT -5
This is going to be another rant about stuff that's happening elsewhere. There are people who don't understand (or deliberately refuse to understand) the concept of heritability and ADHD. They take the numbers - 80% of ADHD is heritable, 20% is acquired or idiopathic - and assume that this is the makeup of ADHD on an individual level.
It's not. It means that in 80% of diagnosed cases of ADHD, there is a clear genetic inheritance. The condition is also diagnosed in a family member (especially a parent or grandparent) and that indicates that it is passed on genetically. In fact, you're more likely to be ADHD like your parent than you are to be tall or short like your parent. It's in your DNA.
The 20% means that in these diagnosed cases, other family members were not found to have ADHD, so there's no direct evidence of genetic causation.
Let me interject something here - that number is now closer to 93%/7%. One of the things that's been changing this is that parents whose children are diagnosed are getting diagnoses of their own in increased numbers. Another thing that's been changing this is the discovery of genetic overlaps; Mom or Dad may not have ADHD, but they have ASD or MDD or EF disorders and the shared genes among these disorders make it so that offspring can express the symptoms conferred by these genes as ADHD instead of the disorder their parents or grandparents do.
The more we research the genetic components of neurological conditions (because DNA builds our brains just as it builds every other part of our bodies) the stronger the evidence becomes that ADHD is something that exists the moment sperm and egg combine, and the only variables are the severity and distribution of symptoms.
_________
There are some people, as I mentioned, who are, instead, insisting that this means you get only a little bit of your ADHD from your family, and the rest of it comes from "the environment." The magical thinking is that if you therefore change "the environment," that ADHD won't "develop." They insist that ADHD can be prevented or cured by "environmental changes" because you've each got that 20% there to work with.
There is so much wrong with this, besides a basic misunderstanding of statistics.
First of all, "the environment." What is that, even? The magical thinkers come up with lots of different ideas, but never quite commit to anything specific. In order to establish causation, you need to find correlation, and there have been no correlations to any well-defined environmental factors, physical or psychological, that hold up to scrutiny. If people have ADHD in the absence of the environmental factor, then the correlation is too weak to assume causation. If people who are exposed to the environmental factor have ADHD in similar percentages to the general population, then the correlation is too weak to assume causation.
I like to use lead as an example. Back before the mid-60s, lead was in everything. Now it's been largely removed. With lead levels well below threshold limits for neurotoxicity, we are still seeing cases of ADHD, and diagnoses are going up. Reverse correlation negates causation. And back when everyone was breathing leaded exhaust fumes, painting their homes with lead, drinking water from lead-lined pipes and. . .well, check out this link to a book on how harmless lead was considered to be. . .there were fewer diagnoses of ADHD (or MBD, as it was called then.) Reverse correlation, no causation.
__________
When you try to point out the logic and the science that supports that ADHD is not something that's "caused by the environment," you're often accused of being a genetic determinist. This is because the people who are misinterpreting how statistics work are also not terribly strong when it comes to understanding genetics. Having the genes means you're more likely to have the symptoms. Having the symptoms means you're more likely to have problems with coping with life with symptoms. This does not mean that you're DOOMED to a horrible life as a failure.
Your symptoms may be few enough or mild enough that you can cope with behavioral strategies. Early childhood interventions and help from parents and teachers can teach lifelong skills. Medications can ease symptoms and improve your ability to actively use the strategies and skills. Modifying the environment in specific ways to teach these skills and reduce the emotional stress that people with ADHD are much more sensitive to can change the severity of symptoms and reduce the level of impairment. But these are treatments, not cures. You can't cure a genetic condition that builds the brain in the womb. Claiming that you can is nothing but false hope.
The other thing is that you can inherit part of ADHD. A few symptoms, but not the whole condition. Or you can end up with a genetically related condition. The variety of outcomes means that a genetic understanding will lead to more effective, individually targeted interventions. Ignoring the genetics and focusing on blaming "the environment" without actually specifying the relevant aspects of "the environment" is like pin the tail on the donkey, but with higher stakes.
_________
Sorry to unload here, but when I try to point this out to the magical thinkers in certain places, I get in trouble for being a meanie-pants who's not "open to considering other points of view." Show me your evidence, I'll consider your point of view. So far, that hasn't happened. Until it does, I'm going with the scientists who've been researching ADHD, in humans, with randomized, controlled, blinded studies, genetic analyses, and research that has scientific consensus.
It's not. It means that in 80% of diagnosed cases of ADHD, there is a clear genetic inheritance. The condition is also diagnosed in a family member (especially a parent or grandparent) and that indicates that it is passed on genetically. In fact, you're more likely to be ADHD like your parent than you are to be tall or short like your parent. It's in your DNA.
The 20% means that in these diagnosed cases, other family members were not found to have ADHD, so there's no direct evidence of genetic causation.
Let me interject something here - that number is now closer to 93%/7%. One of the things that's been changing this is that parents whose children are diagnosed are getting diagnoses of their own in increased numbers. Another thing that's been changing this is the discovery of genetic overlaps; Mom or Dad may not have ADHD, but they have ASD or MDD or EF disorders and the shared genes among these disorders make it so that offspring can express the symptoms conferred by these genes as ADHD instead of the disorder their parents or grandparents do.
The more we research the genetic components of neurological conditions (because DNA builds our brains just as it builds every other part of our bodies) the stronger the evidence becomes that ADHD is something that exists the moment sperm and egg combine, and the only variables are the severity and distribution of symptoms.
_________
There are some people, as I mentioned, who are, instead, insisting that this means you get only a little bit of your ADHD from your family, and the rest of it comes from "the environment." The magical thinking is that if you therefore change "the environment," that ADHD won't "develop." They insist that ADHD can be prevented or cured by "environmental changes" because you've each got that 20% there to work with.
There is so much wrong with this, besides a basic misunderstanding of statistics.
First of all, "the environment." What is that, even? The magical thinkers come up with lots of different ideas, but never quite commit to anything specific. In order to establish causation, you need to find correlation, and there have been no correlations to any well-defined environmental factors, physical or psychological, that hold up to scrutiny. If people have ADHD in the absence of the environmental factor, then the correlation is too weak to assume causation. If people who are exposed to the environmental factor have ADHD in similar percentages to the general population, then the correlation is too weak to assume causation.
I like to use lead as an example. Back before the mid-60s, lead was in everything. Now it's been largely removed. With lead levels well below threshold limits for neurotoxicity, we are still seeing cases of ADHD, and diagnoses are going up. Reverse correlation negates causation. And back when everyone was breathing leaded exhaust fumes, painting their homes with lead, drinking water from lead-lined pipes and. . .well, check out this link to a book on how harmless lead was considered to be. . .there were fewer diagnoses of ADHD (or MBD, as it was called then.) Reverse correlation, no causation.
__________
When you try to point out the logic and the science that supports that ADHD is not something that's "caused by the environment," you're often accused of being a genetic determinist. This is because the people who are misinterpreting how statistics work are also not terribly strong when it comes to understanding genetics. Having the genes means you're more likely to have the symptoms. Having the symptoms means you're more likely to have problems with coping with life with symptoms. This does not mean that you're DOOMED to a horrible life as a failure.
Your symptoms may be few enough or mild enough that you can cope with behavioral strategies. Early childhood interventions and help from parents and teachers can teach lifelong skills. Medications can ease symptoms and improve your ability to actively use the strategies and skills. Modifying the environment in specific ways to teach these skills and reduce the emotional stress that people with ADHD are much more sensitive to can change the severity of symptoms and reduce the level of impairment. But these are treatments, not cures. You can't cure a genetic condition that builds the brain in the womb. Claiming that you can is nothing but false hope.
The other thing is that you can inherit part of ADHD. A few symptoms, but not the whole condition. Or you can end up with a genetically related condition. The variety of outcomes means that a genetic understanding will lead to more effective, individually targeted interventions. Ignoring the genetics and focusing on blaming "the environment" without actually specifying the relevant aspects of "the environment" is like pin the tail on the donkey, but with higher stakes.
_________
Sorry to unload here, but when I try to point this out to the magical thinkers in certain places, I get in trouble for being a meanie-pants who's not "open to considering other points of view." Show me your evidence, I'll consider your point of view. So far, that hasn't happened. Until it does, I'm going with the scientists who've been researching ADHD, in humans, with randomized, controlled, blinded studies, genetic analyses, and research that has scientific consensus.