Asperger’s syndrome originated as a diagnostic label in the 1940s, but the traits it describes have deep roots in genetics, brain development, and prenatal environment. The condition was folded into the broader diagnosis of autism spectrum disorder (ASD) in 2013, so today the question “where does Asperger’s come from?” is really a question about what causes autism, particularly the profile once called Asperger’s: strong verbal and cognitive abilities alongside difficulty with social interaction, rigid routines, and intense focused interests.
The Name and Its History
In 1944, Viennese pediatrician Hans Asperger described a group of boys he said shared high intelligence, social difficulties, and what he called impaired “instincts.” He used the term “autistic psychopathy” to characterize them. His work remained mostly unknown outside German-speaking countries for decades, until British psychiatrist Lorna Wing brought it to wider attention in the 1980s and proposed renaming the pattern “Asperger’s syndrome.”
The diagnosis entered the American Psychiatric Association’s manual (the DSM-IV) in 1994 as a condition distinct from classic autism. It stayed there for nearly 20 years. In 2013, the DSM-5 merged Asperger’s, classic autism, and several related diagnoses into a single category: autism spectrum disorder. The reason was straightforward. A review of 69 studies spanning two decades found that Asperger’s and autism had overlapping signs and symptoms to the point where the distinction wasn’t scientifically valid. A large multisite study of over 2,000 people found that whether someone received an Asperger’s diagnosis depended more on which clinic they visited than on the symptoms they actually had. Genetic research told the same story: the gene variants linked to autism conferred risk for the whole spectrum, not for any particular subtype.
People who already had an Asperger’s diagnosis weren’t left in limbo. The DSM-5 includes a clause specifying that anyone previously diagnosed with Asperger’s should simply receive the ASD diagnosis going forward. Many people still use the term informally, either out of habit or because it feels like a meaningful part of their identity.
Genetics Play the Largest Role
The single biggest factor behind autism is heredity. A meta-analysis of twin studies found heritability estimates between 64% and 91%. When one identical twin has autism, the correlation with the other twin is nearly perfect at .98. For fraternal twins, sharing about half their genes, the correlation drops to roughly .53 to .67 depending on how broadly autism is defined. That gap between identical and fraternal twins is the clearest signal that genes, not just a shared household, drive the condition.
No single “autism gene” has been identified. Instead, hundreds of different genetic variations contribute, each one adding a small amount of risk. These include both inherited variants passed down from parents and spontaneous mutations that arise for the first time in a child. Copy number variants, which are deletions or duplications of stretches of DNA, account for some cases. The sheer number of genetic pathways involved helps explain why autism looks so different from person to person.
What Happens in the Developing Brain
The genetic differences associated with autism shape the brain long before birth. One key process is synaptic pruning, the brain’s way of trimming excess connections between neurons during early development to make signaling more efficient. In autism, this pruning process appears to be disrupted, leaving more connections intact than typical. The result is a kind of neural “noise,” where the brain has trouble filtering important signals from background activity. The degree of disruption varies widely, which helps account for the enormous range of traits seen across the spectrum.
Structural brain imaging has revealed some consistent patterns. The amygdala, a brain region central to processing emotions and reading social cues, tends to be larger in people with ASD compared to those without. Research in young adults with autism found that the white matter tracts connecting the right amygdala to the cortex showed signs of reduced structural integrity. The severity of that disruption correlated with greater difficulty recognizing emotions in other people. Similarly, weaker connections between the left amygdala and the temporal cortex were linked to more trouble shifting attention. These aren’t differences you’d notice on a brain scan in a doctor’s office, but they help explain why social situations that feel intuitive to most people require conscious effort for someone on the spectrum.
Prenatal Environment Adds Risk
While genes set the stage, certain conditions during pregnancy can increase the likelihood of autism developing. The best-studied factor is maternal immune activation, which happens when a pregnant person’s immune system mounts a strong inflammatory response, typically because of an infection. This inflammation can disrupt the energy systems inside developing brain cells during critical windows of growth. A Danish population study found that viral infections requiring hospitalization during the first trimester, including influenza and gastroenteritis, were associated with a 2.8-fold increase in autism risk. Bacterial infections during the second trimester carried a smaller but still notable 1.4-fold increase.
Other prenatal factors linked to elevated risk include obesity during pregnancy, gestational diabetes, prenatal exposure to certain environmental toxicants, and use of specific medications like certain antidepressants or antibiotics. None of these factors cause autism on their own. They interact with existing genetic susceptibility, nudging development in a particular direction. Most pregnancies involving these risk factors result in children without autism.
Who Gets Diagnosed
The CDC’s most recent surveillance data identifies about 1 in 31 children (3.2%) as having ASD by age 8. That’s a sharp increase from earlier decades, driven largely by broader diagnostic criteria, greater awareness, and improved identification in communities that were historically underserved.
Boys are still diagnosed far more often than girls, at a ratio of about 3.4 to 1. That ratio has been narrowing, down from 4.2 to 1 in 2018. But the CDC cautions that the shrinking gap doesn’t necessarily mean clinicians are getting better at identifying girls. The profile of autism in girls and women often looks different: more social masking, fewer obvious repetitive behaviors, and interests that blend in more easily with peer norms. Many women who would have once been diagnosed with Asperger’s are still missed entirely or identified much later in life.
The Neurodiversity Perspective
For much of its history, autism research operated within a medical model that treated the condition as a disorder to be corrected. In the late 1990s, sociologist Judy Singer proposed the concept of “neurodiversity,” arguing that variation in human brains is natural and potentially valuable, much the way biodiversity strengthens ecosystems. Her framework was deliberately positioned as a middle ground between the medical model (which locates the problem entirely inside the person) and the social model of disability (which locates it entirely in society’s failure to accommodate difference).
The neurodiversity perspective holds that disability arises from the interaction between a person’s characteristics and their environment, and that removing barriers and reducing stigma are just as valid as teaching adaptive skills. Curing or “normalizing” autistic people is not a goal. This framework has been embraced by many autistic adults, particularly those who would have previously been labeled with Asperger’s, and it has influenced how researchers choose their language. Terms like “deficit” and “disorder” are increasingly recognized as value judgments rather than neutral scientific descriptions.
None of this erases the real difficulties that come with autism, including sensory overload, social exhaustion, and executive function challenges. But it reframes the question from “what went wrong?” to “how can the world work better for people whose brains are wired this way?”