The Great Divide In Autism Research: Genetics Vs. Environment

By Karen Weintraub
Guest Blogger

 

For years, I’ve been confused about who to believe in the autism research world: the people who say autism is all in our genes or the ones who believe something bad in our environment is triggering a terrible epidemic.

A paper published Monday in the Archives of General Psychiatry seemed particularly appealing, because it argued for a middle ground. Genes are a risk factor, the Stanford University study found, but environment plays a major role, too, accounting for more than half the risk of developing autism.

Argument settled, I naively thought. All this week though, scientists on both sides have continued to snipe at each other.

Millions At Stake
This would be merely an academic argument except that the U.S. government spends well over $150 million annually on autism research. Over the last 10 years, taxpayers have devoted roughly $1 billion to studying genes involved in autism and only about $40 million digging into possible environmental causes. Whoever wins this argument could sway future spending.

Plus, of course, there are millions of families struggling with autism: the communication difficulties, repetitive behaviors and social challenges. Settling this dispute will effect which treatments they try, and what all of us can do, if anything, to prevent autism.

I finally realized today while talking to a geneticist that this difference may never be resolved. The two camps are so distinct – their world views, and the language they use, are altogether different.

Then there are the politics. Mention “environment and autism” and you’re bound to trigger the intense debate over whether vaccines cause autism (a debate that continues despite multiple solid studies that have found no link — though some say research hasn’t yet established whether a small subset of already-vulnerable kids could be harmed by vaccines.)

But if you want to understand autism research and where it’s heading, I think you need to understand where both groups are coming from, and why they can look at the same data and come up with opposite conclusions.

The Great Divide
First, the world according to most geneticists and molecular biologists:

By training and temperament, these folks only trust things they can see and count. If it doesn’t show up in a gene array, it doesn’t exist.

Michael Ronemus fits in this camp. He’s a genetics researcher at Cold Spring Harbor Laboratory, a genetics and molecular biology research institute on New York’s Long Island. He desperately wants to understand autism to help his 9-year-old son who was once diagnosed with the condition, but he’s sticking to what he sees as hard, provable data.

Ronemus thinks we need to first understand all the genes involved in autism before we look to the environmental influences. Knowing which genes are involved will give us clues to the environment, he says. And starting from the environment and trying to work backward is just too squishy.

He wanted to believe, for instance, that eating gluten – a protein in most grains – might contribute to autism symptoms. After all, many parents say their kids improve dramatically when breads and pasta are taken away. But Ronemus says it was hard to get his son to give up those foods, it didn’t seem to help, and none of the autism-related genes that have been found play a role in gluten digestion. So, he scratched that theory off his list. “The things that are in DNA, we can find,” he told me.

To Ronemus, Monday’s study drew the wrong conclusions out of good data.

What Doctors See
The other world view is held mainly by doctors who believe the evidence they see in their clinics, rather than what an abstract number supposedly reveals.

They know that when they came into the profession a few decades ago, they almost never saw a child with autism. One doctor told me he remembered being called into the room during his training to watch an exam with a child who had autism. It was important to see, his supervisor told him, because it might be years before he saw another such child. Now these doctors, see kids with autism every week, if not every day.

They can’t believe that a 40-fold increase in diagnosis is due mainly to an expanded definition of the condition.

To this group, Monday’s Stanford study is validation. “I think it’s going to make the funders wake up a little bit,” said Irva Hertz-Picciotto, an epidemiologist at UC Davis who is firmly in the second camp. “If we’d had this 10 years ago, we’d been a lot further ahead. Hopefully it’s going to change the pattern for the next 10 years.”

The study, led by Stanford psychiatrist Dr. Joachim Hallmayer, pinpoints pregnancy or early childhood as the most likely times for the development of autism.

Now What?

Researchers looking for environmental causes of autism are focusing on five basic areas:

1. Immune problems
Mothers with rheumatoid arthritis and fathers with type 1 diabetes are more likely to have children with autism, suggesting an immune risk. It’s also theoretically possible, but unproven, that a virus the mother catches during pregnancy might contribute to autism (as seems to be the case in schizophrenia); or a virus the child catches early in life.

2. Chemicals in the air, water, food or on the ground
There’s some research suggesting that children of farmworkers exposed to pesticides are more likely to develop autism, and plenty of people are worried about chemicals, like BPA and flame retardants, which are omnipresent and which seem to impact hormones, some perhaps involved in autism.

3. Problems during birth and delivery
There is a possible link between C-sections and autism, and potentially also with the use of pitocin, a drug given to speed the birth process. Complications during birth may also be connected to autism, though it’s not clear whether the complications cause the autism or the other way around.

4. Medications
Another study out this week suggests that antidepressant drugs may be linked to autism, though mothers who are truly depressed may put their child at higher risk for problems by forgoing antidepressants. Also it’s theoretically possible that the “hygiene hypothesis” we hear about in connection to asthma is at play with autism, too. This hypothesis suggests that by cleaning up our environment too much, we’re getting rid of good bacteria along with bad, and could be making our children more vulnerable to new problems.

5. Nutrition
One recent study by Hertz-Picciotto shows that women who took prenatal vitamins just before and in the first two months of pregnancy were less likely to have children with autism than women who didn’t supplement. Researchers are also exploring rates of essential fatty acids, selenium, and molybdenum to see if they might be linked to autism.

The bottom line, according to Dr. Isaac Kohane of Children’s Hospital Boston and Harvard Medical School, is that for now, it’s easier to study genetics – though environment clearly plays a key role. “With genetics, we’re given a very nice hammer and of course something that looks like a nail,” he told me via Skype while on a family vacation. “In environment, it’s not even clear that we’ve found the right hammer. With neither the right hammer nor the right nails, our [research] money might be wasted.”

Hopefully, this week’s study will start to convince people that we need to come up with better ways to study the environment, too.

If you want to read more, see this CDC site that follows autism research, and check out the advocacy group Autism Speaks which funds and follows autism research.

Karen Weintraub, a freelance Health and Science journalist, has just finished writing a book with someone who subscribes to this second world view.

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