Autism and ADHD: Why They Often Go Hand in Hand

Studies estimate that between 50% and 70% of autistic individuals also meet the criteria for ADHD. Conversely, around 10% of those diagnosed with ADHD are also autistic. This means that if someone is autistic, they are more likely than not to also have ADHD. 

 

Historically, diagnostic guidelines did not allow for someone to be diagnosed with both conditions. The DSM-IV (the fourth edition of the Diagnostic and Statistical Manual of Mental Disorders) prohibited simultaneous diagnoses of autism and ADHD. However, the DSM-5, released in 2013, overturned this, recognising what many clinicians and researchers already knew—autism and ADHD frequently co-occur. 

 

The high rates of co-occurrence suggest that autism and ADHD are not just separate conditions that happen to exist together; rather, they have deep-rooted connections.  

 

 

Shared Neurology: Both autism and ADHD involve differences in how the brain processes information, particularly in areas related to executive functioning, attention, and impulse control. 

 

Genetic Links: Research has found that autism and ADHD often run in families, and they share many genetic risk factors. Some of the same genes that contribute to ADHD are also associated with autism. 

 

Similar Symptoms and Traits: Many traits that are considered "core" to ADHD, such as impulsivity, sensory sensitivities, difficulty with transitions, and hyperfocus, are also common in autistic individuals. Likewise, struggles with executive functioning (like planning, organisation, and time management) are present in both conditions. 

 

For many years, people who were clearly both autistic and ADHD were only diagnosed with one condition, often because professionals were hesitant to consider both. This has led to underdiagnosis, misdiagnosis, and a lack of appropriate support. 

 

Now that the overlap is better recognised, many professionals recommend assessing for both conditions when someone presents with traits of either autism or ADHD. Understanding this connection can help individuals and families find the right tools, strategies, and accommodations to thrive. 

 

For those diagnosed with both, it can be helpful to recognise which traits are more ADHD-driven and which are more autistic in nature.  

 

Hyperfocus in ADHD vs. Special Interests in Autism: While both conditions involve intense focus, ADHD hyperfocus tends to be more sporadic and fleeting, whereas autistic special interests are usually long-term and deep-seated. 

 

Sensory Sensitivities: While both ADHD and autism involve sensory differences, autistic individuals often have more predictable patterns of sensory sensitivities, whereas those with ADHD may experience sensory-seeking behaviors in an attempt to regulate focus. 

 

Social Differences: ADHD-related social struggles often stem from impulsivity or distractibility, while autistic social differences are more likely due to differences in communication style, sensory overwhelm, or difficulty interpreting social cues. 

 

Many people with both autism and ADHD prefer to use the term "AuDHD" as a way of acknowledging the unique combination of traits they experience. This term recognises that autism and ADHD don’t just exist side by side—they interact with each other, creating a distinct neurotype that needs its own understanding and support. 

 

Understanding the connection between autism and ADHD is crucial, not just for diagnosis and treatment, but also for how individuals see themselves. Recognising the overlap can provide clarity, validation, and access to better tools for self-advocacy and well-being.