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21 July 2014 - MNT - Autism risk is 'mostly genetic,' according to statistical analysis

David McNamee

Researchers claim that nearly 60% of autism risk is genetic, with the implicated variant genes being common among the general population. They publish the results of their research in the journal Nature Genetics.


This research indicates that the genetic risk for Autism arises mainly from normal variations in many different genes - and furthermore, these gene variants are widely distributed in the general population.

When many of these normal gene variants co-occur in a family, this can be thought of as creating a 'high' genetic risk or 'loading' - although other factors (either rare gene mutations, or adverse environmental factors) need to be operating for autism to be triggered.

Unfortunately, this news article emphasises nothing but 'genetics' - and the headline is particularly unfortunate and highly misleading.

'Autism risk mostly genetic' is enough to make most people think that environmental factors are of little importance. In fact, nothing could be further from the truth, as 'genetic' and 'environmental' factors are always interacting.  

Very fundamentally, the prevalence of autism has been skyrocketing in recent decades - but there has NOT been a similar change in our DNA (i.e. genes) over this period.  This alone shows that the main factors behind the increase are likely to be environmental - and there is also mounting evidence for many of these (e.g. maternal exposure during pregnancy to either pesticides or air pollution appears to increase the risk of autism and related conditions). 

This may be a good piece of research, but as too often happens, the reporting of it - and this news headline in particular - seriously distorts both its findings and their implications.

For more details of this research study, see:

Gaugler et al 2014 - Most genetic risk for autism resides with common variation.

By conducting a "rigorous analysis" of DNA sequence variations as part of the Population-Based Autism Genetics and Environment Study (PAGES) Consortium, Dr. Buxbaum's team found that about 52.4% of autism cases can be traced back to both common and rare inherited variations. By contrast, spontaneous mutations were found to account for just 2.6% of total autism risk.

"We show very clearly that inherited common variants comprise the bulk of the risk that sets up susceptibility to autism," Dr. Buxbaum says. "But while families can be genetically loaded for autism risk, it may take additional rare genetic factors to actually produce the disorder in a particular family member."

The study used data from Sweden's universal health registry to compare about 3,000 participants, including autistic subjects and a control group. The researchers say that PAGES is the largest study of its kind to date.