Unraveling the etiology of autism has been one of the most puzzling challenges in medicine over the past decades. Although in his first description in 1943, Leo Kanner referred to autism as an innate disorder, prevailing views in the years that followed focused on environmental influences ― ranging from cold, unfit mothers to vaccines ― as the primary causative agents of the disorder.

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.

Most people are vastly more interested in the invisible aspects of other peopleʼs actions than in the visible ones. What we generally want to know about others is their “interior workings and invisible aims” ― that is, their beliefs, desires and intentions.

Autism is caused by poor parenting, particularly by ‘frigidʼ mothers who reject their children. Such a statement would seem bizarre today. But 30 years ago parents, especially mothers, were blamed for their childrenʼs autism. Imagine what it must have felt like to be the parent of a child with autism and then to be told it was all your fault. This environment prevailed even after Leo Kanner, who first characterized autism in 1943, assumed it was caused ‘constitutionallyʼ.

n 1997 I took part in a workshop convened by the US National Institutes of Health to sift through the conflicting literature surrounding a rare and then poorly understood disorder known as Rett syndrome (RTT). Although the disorder was first described in Germany as early as the mid-1960s by Andreas Rett, it was not widely appreciated until 1983, when Bengt Hagberg and colleagues reported on a series of similar patients2.

Donald T. was not like other five-year-old boys. Leo Kanner knew that the moment he read the 33-page letter from Donaldʼs father that described the boy in obsessive detail as “happiest when he was alone... drawing into a shell and living within himself... oblivious to everything around him.”