Common genetic variant linked with autism - but with modest effects

A new paper in Nature reports the results of a large genome-wide association of autism. The finding is getting fairly glowing press coverage, but let's keep it in context: an odds ratio of 1.2 means that individuals carrying the variant have their risk of the disease increased by around 20%; their probability of actually suffering from autism is still much less than 1%. This is not a finding that will lead to powerful new diagnostic tools for the early detection of autism, and it's consistent with a generally fairly disappointing yield from studies of common variants in psychiatric diseases. Several recent studies have had much better luck looking at a different type of genetic variant: rare but large insertions or deletions of DNA, known as copy number variants. Coverage elsewhere: Ed Yong has a characteristically thorough run-down on the paper, expanding on a number of important points I haven't covered here.. That headline might give the impression that this variant actually causes 65% of autism cases, which is absolutely not the case: if you read a little further down you will discover that the variant is also present in 60% of healthy controls.)