Is autism more common in Silicon Valley?
A new study from Simon Baron-Cohen and colleagues asked pretty much this question, although rather than California, they looked at Eindhoven in Holland. Eindhoven is the tech hub of the Netherlands:
This region contains the Eindhoven University of Technology, as well as the High Tech Campus Eindhoven, where IT and technology companies such as Philips, ASML, IBM and ATOS Origin are based... 30% of jobs in Eindhoven are now in technology or ICT, in Haarlem and Utrecht this is, respectively, 16 and 17%
The authors found that official rates of diagnosed autism amongst children enrolled in Eindhoven schools were more than twice as high as those in kids from the comparison cities of Haarlem and Utrecht. In Eindhoven, rates of any autism spectrum disorder were 2.3%, far higher than rates elsewhere (0.6-0.8%).
Narrowly defined "classical autism" was also higher. However, two control disorders, dyspraxia and ADHD, were no different.
A diagnosed autism prevalence of 2.3% is extremely high. Some recent studies have found similar figures when you actually go out and attempt to find undiagnosed cases and diagnose them. But for 2.3% of kids to already have a diagnosis, is remarkable.
Unfortunately, there's a big problem here, which is that this study has a sample size is 3. There were lots of data from each city: in total, 369 schools took part, with over 60,000 kids. But there were only three independent cities.
So while these data convincingly show that Eindhoven has higher rates of autism than the other two regions, this might just mean, say, that half of Dutch cities have local educational systems that promote diagnosis, and Eindhoven happens to be one of them.
To really answer the question of whether I.T. folk have more autism, you'd need to look at Silicon Valleys around the world, to increase your sample size.
I'd be surprised if there weren't a link. Autism is highly heritable and we know that the children of people with autism, or mild autistic traits, have a higher rate. I don't think it's too controversial to say that the average programmer has above-average autistic traits, and it's quite possible that a little autism is a positive advantage in IT professions.
This is certainly Baron-Cohen's hypothesis, as he's long argued that people with autism have a tendency to be strong "systematizers":
This striking difference in the prevalence of ASC is in line with the hyper-systemizing theory, and will require the phase two study using diagnostic assessments and screening methods, to determine the exact nature of regional differences in population prevalence. Future research should test if this higher prevalence in a high tech region is found in other cultures (e.g., in Silicon Valley, California)...
Roelfsema MT, Hoekstra RA, Allison C, Wheelwright S, Brayne C, Matthews FE, & Baron-Cohen S (2011). Are Autism Spectrum Conditions More Prevalent in an Information-Technology Region? A School-Based Study of Three Regions in the Netherlands. Journal of autism and developmental disorders PMID: 21681590