Why Autism can be hard to diagnose and why expert evaluation matters

Written by Dr Natasha Russell

Autism Spectrum Disorder (ASD) is a complex neurodevelopment condition that affects how people perceive the world, communicate, and connect with others. One of the most challenging aspects of Autism is that it does not look the same in every individual. It exists on a spectrum, meaning traits can range from subtle social differences to more noticeable behavioural patterns. This wide variation is exactly what makes Autism so difficult to diagnose — especially without the right expertise.

Many individuals, particularly those who have lower support needs or have learned to mask their traits, may go undiagnosed for years. Some are misdiagnosed with anxiety, ADHD, or other conditions that share overlapping symptoms. Just because a child experiences sensory sensitivities, emotional outbursts, or behaviours like hand-flapping does not necessarily mean they are Autistic. These signs can appear in other developmental or emotional conditions too. Gender differences can also make diagnosis more complex. Autism in girls and women often presents differently than in boys — sometimes in quieter, less obvious way — and may be overlooked in traditional assessments.

Another important challenge is that Autism does not come with a single defining symptom. Instead, it is identified by a combination of characteristics — such as differences in social communication, repetitive behaviours, and sensory sensitivities. These traits can vary in intensity and may even change over time, depending on the person’s environment, support system, and experiences. What is considered Autistic characteristics in one person might seem minor or go unnoticed in another.

Tools like the Autism Diagnostic Observation Schedule (ADOS) can assist in the process, but they are not diagnostic on their own. A true diagnosis relies on building a complete picture through detailed history, clinical observation, and expert interpretation. There is no single medical test (no blood work or brain scan), hence diagnosing Autism depends on the skill, knowledge, and judgment of an experienced clinician and a trusted team of allied health professionals.

There can be consequences of inaccurate diagnosis as well, such as long-term mental health impacts, inappropriate educational/funding accommodations, and unnecessary social stereotyping. For families seeking answers, a clear and accurate diagnosis can be life-changing. It is not about applying a label — it’s about understanding. With the right diagnosis comes access to appropriate support, improved self-awareness, and a better quality of life, both at home and in settings like school or daycare.

A good diagnosis should always be comprehensive, compassionate, and tailored to the individual. With the right care and support, families can move forward with confidence and clarity.