by James Hubbard, M.D., M.P.H.

This new study, relating autism to increased precipitation, is a classic “scare of the day” news story.  You will see it everywhere.  Some people will latch onto it as a factual cause of autism, but you will never hear if it is disproven.  Don’t get me wrong.  The researchers should publish it.  It is interesting, but it is a starting point and nothing more.

We know little about causes or risk factors for autism.  So you have to start somewhere looking for clues.  The researchers started with a hypothesis that there could be some environmental trigger.  They scoured state records in Washington, Oregon and northern California, looking for autistic children 6 to 12 years old.  Then they looked at where the child was living and how much precipitation that area got when the child was under age 3. They found that more autistic children grew up on the rainy side of the states. (In case you didn’t know, it rains a lot on the coastal side of these areas, but much less east of the mountain range in the middle.)

But what does that really mean? Rain causes autism?  Nature is against us?  A few years back researchers found that more men with prostate cancer had undergone a vasectomy.  Later studies found it was just a coincidence.  So why do cross-sectional studies like this in the first place?

Because it is a starting point.  Was it some chemical pollutant in the rain that triggered this? Future studies will analyze the rain; scientists will research pollutants to see if there is any known cause for concern (maybe from past animal studies), and someone will see if any other area is exposed to these pollutants–and if there is an increase in autism there, also.  The researchers speculated it could be that the children on the rainy side stayed inside more, so studies may look at chemicals in the house, lack of sunshine and vitamin D, and even amount of TV viewing.

And then it could be a coincidence, with no cause and effect at all.  The researchers did account for race, per capita income and population, but there are many other variables that could account for the regional increased incidence, such as:

• Is there a genetic tendency?
• Did people with autistic children move to or from the area for some reason?  Most of the major cities are on the rainy, west coast side which means more referral centers and support.
• Is autism diagnosed the same in different areas?  It is a clinical diagnosis (no one test can concretely prove “this is autism”).  Some have speculated that a tendency to be more liberal with making the diagnosis may be part of the dramatic rise in the overall number of U.S. cases.
• Do the regional agencies, where the researchers gather their data, differ in how they report autism?

The authors acknowledge at the end of their paper that “further research focused on establishing whether such a trigger exists and on identifying it is warranted.”  Autism is devastating to families.  Most would do anything to avoid it.  But I wouldn’t move to the desert just yet.

Does anyone have comments on autism, speculation on causes, or comments about studies like this?

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Tags: autism, vitamin D

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This entry's content reflects the opinions and reporting of the author and not necessarily that of JHMFD. This entry was posted on Wednesday, November 5th, 2008 at 12:01 am and is filed under Children's Health, Studies. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.