What actually causes autism?

The media is constantly publishing articles about new potential cause of autism, which leads to confusion and general misunderstanding. So what actually causes it? And why do we keep seeing articles like this? Let's dive in to some of the claims!

What do we know at this point?

We know that autism is highly genetic, if not entirely so for many individuals. We are rapidly learning more about the genetics of autism due to Genome Wide Association Studies (GWAS). Back in the day, researchers had to pick a handful of suspicious genes and test people for only a handful at a time. With newer technology that make it easier to sample a person's entire genome all at once, we can now take large groups of people and find areas of genetic overlap between people who have the same traits.

One of the reasons the autism "gene" has been hard to find is because autism is not caused by any single gene! Studies indicate that autism is polygenic, which means there are many genes that collectively contribute to specific autistic traits. This polygenic inheritance pattern explains why autism can look so different from person to person. If there were hypothetically 10 genes that controlled autism (the actual number is much higher, but stick with me here), then someone could inherit gene #3 and not be autistic. \