Autism is diagnosed based on the severity and variety of its symptoms. This makes it very difficult to diagnose and easy to confuse with other disorders, such as language delay and intellectual disability, cautions Isabelle Rapin.

Good mouse models of autism, and accurate tests to assay their phenotypes, are key to both narrowing down a cause and developing effective treatments, argues expert Jacqueline Crawley.

No matter which of the numerous genetic and environmental risk factors has caused autism, the part of the system that is always affected is most likely to be found at the cognitive level, argues Uta Frith, a leader in the field of cognitive neuroscience.

There does not appear to be a single genetic or environmental cause of autism, and given the heterogeneity of symptoms, coming up with a clear yes or no test for autism is challenging. Timothy Roberts argues that imaging and electrophysiology are key in the search for autism biomarkers.

In the new diagnostic manual for psychiatric disorders, Asperger syndrome will be folded into autism spectrum disorder. Francesca Happé, a member of the committee that made the recommendation, explains the rationale behind the decision.

Languages lacking words for feelings can lead to ‘mind-blindness,’ a feature of autism, according to a 2009 study. Cognitive neuroscientist Helen Tager-Flusberg argues that language delay only partially explains the theory of mind deficits seen in people with autism.

In 2003, Stephane Jamain and his colleagues reached a breakthrough by taking a candidate approach to the X chromosome, and linking members of the neuroligin protein family to autism.

In the past few months, researchers have published dozens of reports linking single-nucleotide polymorphisms (SNPs) with susceptibility to a range of common diseases.

It took 50 years for scientists to develop instruments reliable enough to be considered the gold standards for diagnosing autism. Autism has always been around, but it was not until the mid-1940s that Leo Kanner in the United States and Hans Asperger in Austria, both physicians, independently described children with what we now recognize as autism.

In 1985, Simon Baron-Cohen, Alan Leslie and Uta Frith reported for the first time that children with autism systematically fail the false belief task.