Genetic Predispositions and Environmental Triggers
August 14, 2008 by Kristina Chew, PhD
Filed under Health
In the ongoing chicken and egg type debate over what the causes of autism might be, how often have you it said that it’s believed that a child may have a “genetic predisposition” to autism, but that it’s an “environmental trigger”—-it’s something in the environment—-that leads to a child “having autism”?
An August 13th post on Mind Hacks on a letter to Nature on psychiatric genetics offers something to reflect on. From the letter:
Your News Feature ‘The brains of the family’ (Nature 454, 154–157; 2008) and accompanying Editorial ‘An unnecessary battle’ (Nature 454, 137–138; 2008) highlight the need to adopt a more integrated perspective when trying to unravel the biological complexity of neuropsychiatric disorders such as schizophrenia and depression. But the ‘battle’ between genetics and neuroscience, despite being well funded, may be missing the point.
The full version is only available via subscription; Mind Hacks quotes more:
Napoleon Bonaparte advised: “Never interrupt your enemy when he is making a mistake.” Those of us who assess the contribution of non-heritable risk factors to neuropsychiatric illness would like to politely interrupt this battle to remind opponents that environmental risk factors have now overtaken genetic factors with respect to both effect size and the proportion of the population that is affected.
For schizophrenia, for example, factors relating to urban birth, cannabis use and migrant status are well replicated and have relatively large effects — in contrast to the scant evidence that remains after decades of genetics research. Although the ‘heritability index’ for schizophrenia is large (about 85%), this metric encompasses the neglected contribution of gene–environment interactions, as well as the high-profile genetic component. This key point is largely forgotten in the heat of the battle.
Mind Hacks explains” gene-environment interactions” as “where exactly the same genes can produce different heritability depending on the environment.” So, if we all lived in a “virtually identical environment” and had “almost exactly the same life experiences,” genetics alone would have to account for our differences; whereas, if “environment was widely different for everyone, much more of the difference would come from experience.” It’s been noted that studies into the genetics of autism only relate to a small number of cases: If (as suggested in a recent study), different (and many different) genetic mutations lead to autism in different individuals, what other factors might be coming into play, it’s wondered?
Granted, when people talk about “environmental factors” that might “trigger” autism, factors such as “urban birth, cannabis use and migrant status”aren’t what they mean, but rather something more like pollution and vaccines or something in vaccines…….
I realize that lots of people sit around fighting about these things, but recognitions like this–hey! you can have the same genes but different environmental influences can still make you different!–bring only one word to my jaded little brain: Duh.
“Although the ‘heritability index’ for schizophrenia is large (about 85%), this metric encompasses the neglected contribution of gene–environment interactions, as well as the high-profile genetic component”.
Heritability estimates based on classical twin study design has come under increasing scrutiny over the last two decades because of the structural flaw inherent in classical twin study design. Heritabiliy estimates are nothing more than mathematical calculations based on the difference between concordance rates reported in identical twins compared to fraternal twins and the sib risk ratio (multiple family incidence). The problem is that there is no environmental component in classical twin study design and the calculations can lead to false assumptions and misleading conclusions because for any condition where the cause is unkown, classical twin study design cannot differentiate between genetic susceptability and genetic transmission..
The classical example is twin studies in leprosy. Concordance rates reported in identical twins is very high (60-85%) with a rapid decline in concordance rates reported in fraternal twins ( 5-20%). The sib risk ratio of 2.4 is the same as has been reported in autism.
The cause of leprosy, exposure to myobacterium laprae has been known for over 150 years, but the genetic studies in leprosy are a mirror image of the genetic studies reported in autism:
http://www.nature.com/ng/journal/v27/n4/full/ng0401_439.html
Environmental or Genetic, it is written and irreversible, the arrow of entropy and the signal for the end times
That may be, that may be, and what’s gonna happen ’s gonna happen to me, that’s the way it appears.
To be honest the world would be better without 90% of the researchers, they are not really pushing the frontiers of anything and are a self sustaining industry no more.
Not believing that vaccines are involved in the etiology of autism does not preclude believing that there are environmental factors that are involved in autism development. In fact, I would go far as to say that everything about our overall health and development is the result of a combination of genetic predisposition and the environment to which we are exposed. I suppose that there are purely genetic diseases (such as CF, sickle cell anemia, Down’s syndrome, etc), but most of these diseases can be traced to a single gene mutation (or in the case of Down’s syndrome, an obvious genetic error), but in the case of polygenic diseases (such as autism), I think that it’s highly unlikely to be the result of pure genetics.
One complication with autism is that it’s not that one gene that can be pointed to, as in Down’s Syndrome.
And the “environment” is such a huge term and entity; if we weren’t living at a time when there were so many concerns about global warning and “going/being green,” would we be so concerned about “the environment and autism”?
The ‘environment’ includes prenatal factors, uncontrollable factors, co-morbid conditions… I seriously doubt it has anything to do with vaccinations, since the autism rate is the same for both vaccinated and unvaccinated kids.
Ok lets get the air cleared, my Tomfoolery betokens no allegiance to Shakespeare (cryptic clue)
Ones language choice does betray ones attitude often and whilst I agree that the environment can’t be ruled out and genetics is a bit of a wild goose chase in the bigger picture, to call something a disease is to suggest it is unnatural, notwithstanding virii and bacteria are also epigenetic and environmental factors that have been around longer than we have.
The environment determines us all as we determine it, we are locked into a symbiotic relationship and nothing is natural and unnatural, it merely is or is not.
Even Dawkins who thinks he does not need a weatherman to tell which way the wind blows would go to a visually impaired horologist if there were no one else in town to fix his instrument.
The nuclear bomb is a natural outcome of evolution surely if you follow his line of argument, cos we evolved simply because we did and everything we make has to be a product of evolution too, ne’st ce pas, and thus the whirligigs of time bring in there revengers but that’s all one and our play is done and I’ll strive to tease you every day.
Hey Tommo, I’m watching out for you this September, got any new controversies …. wanna buy an argument?
Debating causes, while important to future parents, often feels like society is ashamed to have “us” walking about the streets.
Also, the time and money invested in some causation research would help a lot of people if it were spent on education and treatments of comorbid conditions.
I do not doubt a genetic component, but I also believe triggers can result in “autistic” traits. Genetic does not always indicate a familial trait, since errors can occur randomly. It seems absurd, like so many things, but defects sometimes just happen… absurdly random and cruel.
I’m in the camp that fears testing for autism. But, I also am fairly sure the day will come. “Your child has a 60% chance of…” and there you have it. “Gattica” comes to mind.
I don’t think searching for a cause indicates that people are necessarily “ashamed” of autistic individuals- I have been involved in type 1 diabetes research for many years (looking for the “cause” and also for a “cure”), and I have never felt that any of the patients that I worked with were ashamed of their disease, and certainly that’s not what’s driving the research community. It’s important to spend the money on education and on treatments, but understanding what causes the condition would help us figure out what treatments would be the most effective.
I find the information in the comments in this massage board. I think that we nave been though this before on the thread [every thing causes autism] where I said that there were four elements to the autism proublem. You start with trhe man made flouride [lead and arsenic] then add chlorine to the water that pregant mother drinks and cooks with. Then add the thimerosal with the first shots. Evey body knows what lead and mercury from the 1980s when the gov took the lead out of gas and paint {where we all saw the little girl eating the paint chip. We Know that diffent cities put man made fluoride in water supplys seance the 1940s tell there were about 50 cities had it in 1991 when the gov told all cities with over 5000 pop to put the man made fluoride into the water, now there are over 2500 to 3000 cities with man made fluoride. This is left over waste from making fertilizer, that the EPA would not them to put in a dump for fear that it would get in to the under guound supply that may people might get in there wells. But the EPA did the testing and said that it was ok for drinking water.
But there never has been a time when human beings and animals have not lived in and had to adapt to a toxic world.
Ergot in Rye, lead pipes, arsenic wallpaper, radium ,never mind what passed for medicine in more primitive times than our own, notwithstanding the industries of the time without protection the mining of heavy metals.
What is new?
Life used to be (Hobbes again) Nasty Brutish and Short, even for Kings, you do not want to know what there physicians did for them.
Where is this golden age of harmony with the environment?
We have always been exposed to cosmic radiation, and natural radioactivity from radon gas. Archeology depends upon that for dating of bones, and archeology also reveals just what the heck was going into peoples bodies, a lot more than thimeserol I can tell you.
Lrex, have you ever read what they fed poor James I/VI as a baby? It’s a wonder that man ever lived to rule England and Scotland. And as for everyone else, the widespread application of arsenic and mercury alone should’ve killed ‘em all.
“urban birth, cannabis use, and migrant status”
Hippies! That patchouli makes my nose itch!
Please don’t hit me, but I agree with Doc Savage that whatever is right or wrong with you is about 1/3 genetic, 1/3 environmental, and 1/3 God only knows.
I’ve heard a “cure” parent say that someday autism and its traits will be eradicated. All the traits? That’s what I ponder… and don’t have an answer for.
Am I my genes? I’m sure some of my skills are genetic, since relatives I have never met (my father’s parents divorced when he was very young) are in similar professions, have similar hobbies, and are curiously like myself — “geeky” and “odd.”
Am I my experiences? Definitely. My views on teaching and therapy were shaped by the bad experiences I had as a young student and as an adult in a doctoral program. My politics were shaped by the intolerance of academic “liberals” who disparaged me, my family (”trailer park trash” was actually said by a teacher who thought I didn’t hear her), and my disabilities.
Am I something else? Though an atheist, I like the “1/3 God only knows!” description. I’ve met “evil” people from great families and near saints from horrible situations. Some things just can’t be explained.
It was following a Minnesota Public Radio forum that a parent said she would have terminated her pregnancy if there was a “good chance” (what’s that?) of autism. Personally, I think she’s a “good chance” of raising a narrow-minded child.
As Prof. Chew has indicated, there are very real concerns for existing children with autism: education access, adult care, and more. A lot more. But, we’ll be spending money testing whatever Kirby and Company promote as the cause of autism.
After reading the postings on the theard there so many good things to think sbout that I don”t know where to start. But seance we have not heard fron stockdoc I got some thing for her. May you could answer a question for me.As you kow that I say that the man made fluoride in the water that may be cause for autism as I said in a posting above. I left out one thing what if the water that the little shootgin rider is doning the back stroke in has a high amount of ammonia and some gets into the brain though the soft spot on the head though osmosis could that have an effect on the brain?
Hi laurentius rex; I don”t know what kinds of ads in Coventry because the after you take the medicine you could have more problems then you started with. You said that you have fluoride in the water is it man made, and when did they put in. How big of an area does the water supplyer cover you might find how many people live in that area. If you read all the posting and all you can see the word thimerosal at least just this guy saw it was 1/3 of the problem.
C.S.Wyatt; Just because that you have curiously that does not mean that you are a geek it just like known what is going on around you, as you can see that I have lot of curiosly myself. Some people may think I am odd but I just see myself as a aquarius.
Yeah we have flouride and that wasn’t there to start with (probably was not there when I was younger) as for the rest of it, it is everything that everyone upwind of Gloucester pees into the river via the sewage works, that is every drug that was ever prescribed in microscopic amounts.
@Emily, so what did they feed James?
@CS Wyatt, yes I do think some kind of prenatal genetic test will appear at some point maybe even soon—hope that understanding about autism might keep growing so people can make the right decisions.
Kristina…beer and oats, if I remember correctly. When he was an *infant.* He looked sickly, apparently, and that was the “cure.” He must actually have been quite tough to survive that.
Whenever I read my favorite century literature (the 19th), I’m always astonished at the amount of alcoholic beverages people of all ages consume. Just finished Dombey and Son, and the delicate “son” of the title receives porter rather than small beer at the midday meal (he’s about six) because of his delicate constitution. The hope was that the porter would give him more strength.
Anyway…imagine what all of that ethanol was doing to those young, growing minds. And there’s also reference in that novel–very casual, it’s-totally-normal type reference–to a pregnant woman getting in her cups.
And as I understand from talking to “the husband,” in the not-too-distant past (as in this century), expecting moms were known to imbibe. Beer in one’s oatmeal, lovely combo! (not that they were thus consumed)
Off-topic, am a huge fan of George Eliot and Thomas Hardy.
Oh, yeah! Back when, pregnant women were encouraged to drink beer, for the B vitamins which were in it. Back before our refined and etiolated beers, that is.
I can’t believe a pint of organic stout every week or so would harm Mom or foetus, and might do them both good. You betcha all of my female ancestors up until maybe 1800 followed that plan.
The reason for the predominance of beer drinking in the past is simple, the water could not be trusted to drink and the side effects of alcohol intoxication were a lot milder than the consequences of typhoid or cholera.
No species ever operates at its cognitive, or physiological maximum, there is a wide degree of tolerance to a hostile environment, it is in the big picture what matters, and the fact we are all here demonstrates that. One simply cannot eliminate all risk, as soon as we do something unexpected comes along, it is like the old story where the guy rides halfway accross the world because he saw death coming for him that morning in the marketplace. He meets up with death just the same, who tell him, that he was puzzled as to why he was so far away from there appointment in the morning.
Oh, in Samarra? That’s close to home for me, I being an American and my country’s army operating there.
Oh yeah on the beer, you have to boil the water first, and then you put in the alewort (ivy) and later, hops, as disinfectants. I do love me some India Pale Ale, with LOTSA hops! I could do with less alcohol in it, though.
I think hops have a calming influence on me. I think that I did read somewhere, that George III, when he was having his mental problems, could not get a good night’s sleep unless he laid his head on a pillow stuffed full of hop blossoms.
Hops are a member of the Hemp family related to guess what?
c.s.; I also feel sorry for the childern with and there faimly, but I just would like to see alo fewer of them over time. I am like you I would like to know what genius thought it might be the environment now are they the geniuses that for years said it was in genes or caused by the thimerosal in the vaccines. You just have to wounder what they will thank up to study this time. I bet it will be some thing very strange or far out like pixy dust whitch will be hard to find. I remembered some thing you said in yor other post about the teacher said about trailer park trash, just look at it this way if you know about it you must have been the youself.
I wish I had read the Boston Globe article before i worte the other post.Becaue I like what they said that there where no obvious things to track, so the first things where going to be pesticdes then going to sickness or even if they were sick when they a child os back to genes. The one thing Ididn”t was any thing to do with the water with MAN MADE FLUORIDE in it with its [lead and arsenic]. Like said before that they will be lookig for some that effects a few and apply it to all. But I don”t think that speaying in Calf. is going to have the same effect on some one in down town Hackensack NJ. The only thing I maor aless agree on is that you keep on drinking the water with the {lead and lead] you keep opening the sore on that gene tell it may so damaged that it may not be able to recover or even get worse then we know what the end game will be.