Friday, September 08, 2006

GENETICS AND THE ENVIRONMENT

I want to draw your attention to some good reading out there bearing on the question of the respective roles of genetics and environment in causing autism spectrum disorders.

Dr. Julie Daniels, an Assistant Professor of Epidemiology and Maternal and Child Health at the University of North Carolina, wrote an editorial published in the July 2006 edition of Environmental Health Perspectives that is well worth reading. (Thanks to María Luján for bringing it to my attention.) Dr. Daniels notes that:
Speculation that the environment plays a role in the development of autism primarily comes from two observations: a) although concordance among monozygotic twins is high, it is not perfect, and a specific “autism gene” or set of genes has not yet been identified; and b) the prevalence of autism is higher than previously thought-if it is rising, the rise might be associated with a shift in the environment.

Dr. Daniels displays far more logic than one is accustomed to hearing in our little debates, when she writes that the confounding of causal research is the likely result that what we call ASD may result from a variety of gene-gene and gene-environment interactions. Although conceding that the “perception” of increased prevalence may result from changing diagnostic criteria or increased availability of diagnostic tools and services, she also acknowledges the possibility that we may be seeing a true increase in prevalence. There is little in the way of “systematically collected data in the same population over time that can be used to evaluate true prevalence rate trends.”

After stating that environmental factors could explain true shifts in prevalence, and further noting the difficulty in assigning causal based on ecologic associations, Dr. Daniels writes the following, which I partly agree with:
It is unlikely that one or even a few specific environmental agents are responsible for the majority of ASDs. It is more likely that some individuals have enhanced susceptibility to insults from the environment that may, in combination with their genetic predisposition, lead to autism. It is rarely possible to distinguish these complex relationships by simply evaluating trends in the general population.

The much publicized concern over vaccines and autism has primarily been based on such ecologic trends. More rigorous studies evaluating vaccine-related hypotheses are needed to incorporate individual-level exposure data, account for alternate exposures to metals, and evaluate susceptible subgroups of the population. However, attention should also be given to other environmental hypotheses.

Although I agree that environmental insults other than vaccines and thimerosal need to be considered, I think Dr. Daniels underestimates the probable connection of the single most pervasive exposure to a generation of children. Nevertheless, I am delighted that a respectable epidemiologist recognizes the limitations of the epidemiological evidence and is displaying an open mind on the question.

To state the obvious, I think the more we learn about the processes of autism, the more clear the causal connections will become. If well-designed research shows I am wrong in my opinions, I can live with it. What I can't stand, however, is the tendency of so many scientists to bury their heads in the sand. Dr. Daniels' willingness to follow where the science may lead is refreshing.

And that brings us to some exciting things going on in the study of neuroscience as it relates to autism. One of the most interesting presentations I saw at the Autism One Conference this past May was by Dr. Manuel Casanova, who has been researching the differences in minicolumns between brains of autistic individuals and neurotypical persons.

Ian Parker, takes a detailed but very readable look at Dr. Casanova's work, and reaches conclusions that sound consistent with what was reported at Autism One:
Reduced minicolumn width appears to be a prerequisite for autism. But, the reported minicolumn widths found within autistic brains are still within the normal distribution of minicolumnar width, albeit at the tail end (Casanova 2006). This suggests to me that the existence of narrow minicolumns is not enough by itself to result in an ASD diagnosis. The key instead appears to be a reduction in inhibition within minicolumns, rather than width alone. Reduced width increases the consequences of reduced inhibition, but does not automatically cause it. In effect, a brain with narrower minicolumns may be less robust, and therefore more vulnerable to the complications that could come with deviation from the narrow tolerances within which the brain functions. In a brain with wider minicolumns, a loss of inhibition would not have as significant an impact, as minicolumnar width (and therefore distance between minicolumn information processing cores) would still exist to reduce intercolumnal spill, and thalamic projections would result in fewer minicolumns per macrocolumn to be affected.

Even with reduced minicolumn width, a “second hit” is required for there to be a manifestation of dysfunctional autistic symptoms. Ian's conclusion suggests that the notions of a cure and maintaining neurodiversity may not be mutually exclusive. Read it here. (The conversation taking place in the comments will make your investment of time doubly worthwhile.)

13 Comments:

Blogger Fore Sam said...

The dilemna for neurodiverse adults is that they have never experienced normalcy. They don't accept the fact that most of them were born normal and they have nothing to fear. They don't believe that their brain power will be intensified when it is no longer affected by mercury. It's sad that they have been conditioned this way by the ignorance of those who continue to tell them there is no known cause or cure for autism.

9/9/06, 10:14 AM  
Blogger Kristina Chew said...

Dr. Daniels' editorial is a thoughtful and responsbly written read--thanks too to María for the links.

9/10/06, 9:55 PM  
Blogger Ian Parker said...

Hi Wade,

Thanks for the great plug, the link, and the write-up on the Daniels editorial (which I quite like).

Over the weekend, three things became linked in my mind. First was this post. Second, I took the Bear to a children’s hospital outpatient lab on Friday to get blood work done. Included in this was a third red blood cell trace elements test and a urine test. We had a first test done as part of earlier blood work to test her essential trace elements, and ticked the toxic panel at the same time (the lab evaluates everything and reports on what is requested, so there was no additional work involved). The toxic panel results came back alarmingly high (not Hg, but a couple of other elements). We took the results to our pediatrician, who contacted the provincial poison control office and authorized a second test and a urine test. The blood test came back lower, but still more than twice the upper limit. The urine test also had a few nasty surprises that weren’t part of the blood test. But yet we could get no one to even give the results more than a cursory glance.

As soon as the poison control found out that the Bear was autistic, they wanted to wash their hands of the results, even though they had requested the pediatrician to conduct the second test. We were accused of trying to get them to do chelation on her, at which point I replied that if we had wanted to do chelation then we easily could have and would have done so long ago, and ignored the mainstream route completely. Instead, we came to them to get a mainstream look at the issue. We did get the pediatrician to reluctantly agree to a third test, which we batched up with other blood work (the Bear has other mainstream-recognized issues) and had drawn on Friday. Of note, all of the tests have been and/or will be conducted through government funded provincial health labs.

The third thing was a news story on Sunday night. Apparently there is some concern regarding pollution levels off the coast of New Brunswick contaminating local shrimp. A study is being done to examine the effects of environmental pollution, to determine any impact on the shrimp population.

So how do I get the shrimp researchers to examine the Bear?

9/11/06, 1:57 PM  
Blogger ballastexistenz said...

And fore sam has never experienced autism, yet seems determined to think it's a bad thing that he wouldn't want to be. Hmm...

9/17/06, 11:42 AM  
Anonymous Anonymous said...

ballastexistenz, it's great that you're happy being yourself. But how do you feel about younger children who have a CHANCE to be much more neurotypical than they are now...with the proper interventions?

Wouldn't you want for them things like the ability to live independently...both financially and otherwise? Wouldn't you want them to be verbal...have friends... maybe have a career, get married (should they choose)?

Without the science that biomedical researchers are exploring, these opportunities won't happen for a majority of severe autistics.

In no uncertain terms...I do NOT want my daughter to have your limitations when she reaches your age.

Erik

9/18/06, 10:00 AM  
Blogger Alyric said...

Erik wrote:

"In no uncertain terms...I do NOT want my daughter to have your limitations when she reaches your age."

And in no uncertain terms, I do not want my daughter to have yours.

9/19/06, 10:18 PM  
Anonymous Anonymous said...

Care to clarify your sarcasm, Alyric? Enlighten us as to why autism should be celebrated? Why should we allow children's brains to remain damaged? Do you like the neuronal death due to mercury toxicity and the microglial activation occurring everywhere? Do you like measles viruses infecting the guts of these kids and entering their spinal and brain fluid? How about the painful, acidic diarrhea? Is that what's so good about Autism?

And when these children grow out of the gut problems, but are left with mishapen brains... and can't support themselves, needing to live in a group home... are you going to throw them a party and say "good for you and your beautiful autism!"

That's NOT what I want for my daughter, in no uncertain terms. She deserves BETTER than what you would have her suffer through.

Erik

9/20/06, 8:42 AM  
Blogger mommyguilt said...

Ok, I'm going to leave that conversation to Erik & Alryic. I found Dr. Daniels' editorial very interesting. My thoughts are these:

Odds are in my lifetime, no matter how much research is done on any factor, environmental, genetic, both, we're not going to pinpoint a cause. I have NO clue why my son is on the spectrum but his brother and sister are not. Everything was the same post-partum as far as vaccines, everything was the same before birth - environment, diet. The only thing blatantly different were that SmallBoy was 4wks early, and thank God, because his umbilical cord was tied in a knot. Could THAT have contributed, or was it truly a genetic thing that skipped my other two?

We'll never know. But I agree that yes, due to the unbelievable rise in autism cases, there has to be something out there that is changing. I also agree with Dr. Daniels' quote:

"It is unlikely that one or even a few specific environmental agents are responsible for the majority of ASDs. It is more likely that some individuals have enhanced susceptibility to insults from the environment that may, in combination with their genetic predisposition, lead to autism."

THAT, right now, seems to make the most sense. I'm not disagreeing with the vaccine theory, I'm not disagreeing with the genetic theory, nor am I disagreeing with the environmental theory.

What I do agree with, as do the rest of you regardless of the school of thought to which you subscribe, is that if we want autism numbers to decrease and, ultimately, disappear, we're all going to have to stop arguing about the causes and the this, that, and the other, and begin educating the rest of those out there about autism. We need to start working together, joining our theories to continue investigating...to find a cause. Without the cause, we're not going to find the cure.

So, what say y'all stop arguing. None of us likes autism. I look at my son and yes, I see a beautiful child who is doing his damndest to lead a successful life, but I HATE autism. Let's put our collective heads together and all the knowledge that we've each gained on environment, genetics, vaccines, metals, predisposition, and let's do something together.

Done ranting now. Ian, I'm on my way over to check out your post.

9/21/06, 10:53 AM  
Anonymous Anonymous said...

Mommyguilt, I know exactly what caused my daughter's autism. It's not a confusing thing.

What's confusing is how to repair the damage to her gut, nervous system and brain.

Erik

9/21/06, 2:10 PM  
Blogger mommyguilt said...

Erik, and every other parent, I pray that we can find a way to repair all of these horrendous physical things that autism does to our children.

I also hope to God that we can find a way to repair the emotional & psychological damage done to our children by those who don't want to or can't understand. My son has been shunned by my Ex, just since the dx - 2yrs ago, he's 10 now.... He still sees my two older, NT kids..., picks them up from my house while my poor SmallBoy watches them go and cries, and says he's a bad boy and no one loves him. THAT hurts too. Before the dx, he always took him. Now, he says he's a bad kid, a danger to his 1yr old son (SmallBoy wouldn't hurt a flea), and that he just lies and won't listen and yells back. Come ON!

So, that explains my mission of educating. Finding cures and solutions to the god awful things that come with ASDs is SO hugely important, I agree with you completely. Along the way, though, let's make sure that we raise awareness...the more people who know, the better chance of someone pitching in to help, the better the chance of finding a cure.

9/22/06, 2:44 PM  
Blogger Fore Sam said...

Mommyguilt;
Will your ex go online and talk to some other fathers to learn that he should be angry about the fact that his son was most likely poisoned? It's beyond me what goes through some guys heads who aren't actively trying to help their kids.

9/24/06, 9:27 AM  
Blogger mommyguilt said...

Hey Fore Sam - see my comment on your blog. But no, my ex won't do that...he's too stubborn - or perhaps pigheaded is the appropriate word.

9/26/06, 10:06 AM  
Anonymous Anonymous said...

My 4 year old daughter was just diagnosed with PDD-NOS. I was researching umbilical cord true knots and autism to see if there was any connection. It was a surprise to the midwife when she was born and saw a true knot in the umbilical cord.

1/17/07, 11:40 PM  

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