Special Reports Curated collections of articles on special topics in autism.
Illustration by
Laurene Boglio

No one knows exactly what lies at the root of autism — but that hasn’t stopped scientists from speculating. Like the condition itself, the theories of autism are diverse.

Some theories attempt to explain its traits at the level of genes; others look at alterations in brain activity. Still others focus on the psychology of the condition. Two leading theories attempt to explain the skewed sex ratio in autism — why the condition is diagnosed more often in boys.

In this special report, we explain some of the most popular hypotheses of autism’s origins.


Featured Articles

The signaling imbalance theory of autism, explained

by  /  1 May 2019

The signaling imbalance theory holds that the brains of autistic people are hyper-excitable because of either excess neuronal activity or weak brakes on that activity.

A DNA helix showing common and rare variants

The multiple hits theory of autism, explained

by  /  1 May 2019

Researchers are studying how a combination of genetic ‘hits’ may contribute to autism’s diversity.

overlapping network of connections in the brain

The connectivity theory of autism, explained

by  /  1 May 2019

A growing body of evidence suggests that autism involves atypical communication between brain regions, but how and where in the brain this plays out is unclear.

The female protective effect, explained

by  /  1 May 2019

One of the leading theories of autism posits that girls and women are biologically protected from the condition.

Illustration of a strong man holding up a oversized brain

The extreme male brain, explained

by  /  1 May 2019

The ‘extreme male brain’ theory suggests that autism is an exaggeration of systematic sex differences in ways of thinking.

Illustration shows the world is distorted through a point of view pair of glasses

The predictive coding theory of autism, explained

by  /  1 May 2019

In autism, a person’s brain may not form accurate predictions of imminent experiences, or even if it does, sensory input may override those predictions.

Illustration of red figures on a big blue brain are serotonin signaling

Serotonin’s link to autism, explained

by  /  1 May 2019

Serotonin, the brain chemical best known for its link to depression, may also be involved in autism.