Untangling the many different causes behind autism spectrum disorder (ASD), now estimated to affect one in every 68 children, is a hefty and as yet unfinished task for scientists around the world.

But although that research is still ongoing, there are some promising explanations we’ve settled on, as well as some debunked duds. Let’s take a look at them.

An Early Start

Autism is a complicated neurological condition involving developmental and learning disabilities that can dramatically vary in severity, from problems with social interaction to being unable to process sensations like touch normally. And it’s caused by a variety of risk factors that interact with one another in ways we still understand little about.

What we do know is that many of these factors happen very early on in life. Some researchers have found many, if not most, autism cases can be traced to someone having common genetic variations or rare spontaneous mutations. Boys also appear to be at higher risk, but it’s possible that girls are simply being underdiagnosed.

Other scientists, while not disputing the role of genetics, have found evidence that a developing fetus’ environment (i.e. the womb and mom) can influence autism risk. These include the mother’s exposure to smoking or air pollution, her gaining excess weight, and whether she’s an older or teenage mom or there's a large age gap between parents. Babies prematurely delivered also appear to have an increased risk of autism and other neurological conditions.

Debunked And Unlikely Causes

Again, there’s no one single cause of autism, just things that make someone more likely to develop it. But there are definitely factors we know probably don’t contribute to autism risk. These include vaccines, whether a children was delivered through cesarean section, and most recently induced labor.

There are also some potential but still highly debated and outright iffy theories, such as antidepressant use during pregnancy, aerial pesticide exposure and, believe it or not, having a circumcision.

While we may never have a perfect understanding of what causes autism, we’ve certainly made a lot of progress since the earliest days of research in the mid-20th century. Back then, it was simply assumed that frigid mothers who mistreated their children were the culprit.