23/02/2026
If autism is genetic, why am I the only one diagnosed in my family?
This is a question many adults ask when they begin considering an autism assessment, or after receiving a diagnosis later in life.
Research shows that Autism Spectrum Disorder has a strong genetic component. Large twin and population-based studies estimate that genetic factors account for a substantial part of the likelihood of autism, commonly reported between about 50 percent and 80 percent.
However, genetics do not work in a simple or predictable way.
There is no single “autism gene.” In most cases, autism reflects the combined influence of many genetic variants, each contributing a small effect. In a smaller number of cases, autism occurs alongside specific genetic conditions. Overall, inheritance is complex rather than straightforward.
Within the same family, one person may meet criteria for Autism Spectrum Disorder. Another may have certain autistic traits but not experience clinically significant impairment. Another may not show noticeable features at all.
Two factors are often overlooked.
First, the way autism has been recognised and diagnosed has changed over time. Many adults grew up when autism was mainly identified in children with more clearly visible differences or higher support needs. Individuals who spoke well, performed well academically, or learned to copy social behaviour were often not assessed. In some families, traits may have been present in parents or grandparents, but no one received a formal evaluation.
Second, differences were sometimes understood through other frameworks, such as personality style, anxiety, depression, or other mental health explanations, rather than being explored within a neurodevelopmental context.
Being the only diagnosed person in your family does not contradict the genetic evidence. It reflects the complexity of inheritance, the evolution of diagnostic systems, and the role of context in who is recognised.
If you are wondering whether your experiences may align with Autism Spectrum Disorder, a comprehensive adult assessment includes a detailed developmental history, a structured clinical interview aligned with DSM-5-TR criteria, and careful consideration of alternative or co-occurring conditions.
If you are already diagnosed and seeking ongoing, affirming psychological therapy, therapeutic work may focus on identity development, relational patterns, sensory regulation, and sustainable functioning.
Our team of registered Clinical and Counselling Psychologists specialise in adult autism and ADHD.
For more information or to book an appointment
🌐 https://spectrumcentre.co.za/
📧 hello@spectrumcentre.co.za
We specialise in Adult Autism diagnosis and long term therapy. The Diagnosis is conducted over 2 sessions by one of our Autism (Neurodiversity) Specialist Psychologists. The diagnosis process consists of a Clinical Interview based on the diagnostic criteria of ASD Autism Spectrum Disorder as specifi...