ADHD and autism are commonly comorbid conditions, with research showing that over 40% of patients with autism spectrum disorder (ASD) also present with attention deficit hyperactivity disorder (ADHD) at some point. The reason for the relationship between these two disorders is still largely unknown, but with the right cognitive testing tools, providers can understand how the conditions present in individual patients to make more confident diagnoses and deliver more effective personalized care. 

Both conditions are categorized as neurodevelopmental disorders, a category within which it is common for patients to experience comorbidities. Until recently, it wasn’t possible to diagnose autism and ADHD concurrently, leaving a limited scope for large-scale research on cross-condition association.

So, what are the similarities and differences between ADHD and autism spectrum disorder? What are the defining features, and how can digital cognitive testing help providers access the objective insights they need to make the distinction or diagnose the two conditions when they present simultaneously?  

Difficulty Differentiating Autism and ADHD Symptoms 

To appropriately diagnose and build treatment plans for patients, providers need accurate insights into whether or not a patient is experiencing autism, ADHD, or both—and which symptoms of each disorder they’re impacted by or experiencing.  

Adults with ASD and ADHD can exhibit similar subjective clinical symptoms, making it difficult to differentiate the conditions without a thorough assessment. The accurate and effective diagnosis and management of both disorders are essential for children and adults with these disorders to thrive. Confident diagnosis starts with effective assessment. To properly assess patients, providers should understand the complexities of the two disorders—how they overlap and how they differ. 

Overlapping Symptoms of ADHD and Autism Spectrum Disorder

There are many clinical symptoms of both ADHD and ASD that overlap. Some of these overlapping features include:

• Attention deficit and overactivity: Many patients with both ADHD and ASD struggle with attention and activity regulation.
• Behavior problems: Many ADHD and ASD patients demonstrate behavioral problems in childhood. That being said, comorbid oppositional defiant disorder, anxiety, and cognitive difficulties in ADHD patients may also explain this overlap in some patients. 
• Difficulty with social skills: Both ADHD and ASD patients can struggle with social skills.

These overlapping symptoms can make it easy to mistake one disorder for two. One study found that while the two disorders are distinct, there is a similarity in clinical symptomology. Notably, the study excluded individuals with comorbid ADHD and autism spectrum disorder, but still found that the Autism‐Spectrum Quotient (AQ) score was elevated in individuals with ADHD, suggesting that some individuals with ADHD may present with symptoms typically associated with ASD.

Both autism and ADHD patients may report symptoms related to attention. However, attention can be broken down into more specific abilities that differ between groups. For example, people with autism may have difficulty with shifting focus, but people with ADHD may shift focus too easily and be described as easily distracted. Both groups struggle with attention, but in different ways, making it important to assess multiple aspects of attention to disentangle symptoms.

This overlap in symptomology makes it necessary for providers to use other methods of assessment in addition to standard questionnaires. 

Challenges in Diagnosing Autism and ADHD 

There are many challenges in diagnosing ASD and ADHD. In addition to difficulties discerning overlapping symptomology, social realities can play a major role in delaying or preventing diagnosis. These are just a few of the key social factors that can impact ASD and ADHD diagnoses.

Patient Masking

Masking refers to a series of coping mechanisms in which patients with neurodevelopmental conditions like ASD and ADHD hide their symptoms to fit in socially. While these coping methods (like forcing eye contact or stifling stimming behavior) may be initially helpful, over time, they can be harmful. In addition to potentially creating a disconnected sense of self, masking can also make it difficult for providers to properly diagnose older children and adults. 

Stigma

Even as awareness grows, social stigmas still prevent many people from seeking and receiving the diagnosis and care that they need. People may face negative stigma related to ADHD or autism. This may be regarding symptoms, behaviors, and medication use. Like with any health condition, stigma can prevent patients from seeking help.  

Age-Based Differences

ASD and ADHD can show up differently in different age cohorts. Using a single diagnostic criteria for all age groups is likely to result in misdiagnosis and inappropriate care planning. 

Gender-Based Differences

Like age, gender impacts the appearance, expression, and presentation of neurodevelopmental conditions. For ADHD, the diagnostic criteria were originally developed to describe the condition in boys, which is problematic as girls and women with ADHD may present with different condition profiles and symptoms than their male counterparts. 

Girls and women with ADHD tend to predominantly present with inattention and associated internalizing problems, whereas boys and men are more likely to display overt symptoms like hyperactive-impulsive symptoms. Limited awareness of gender differences can result in delayed diagnosis for girls and women and, in turn, delayed care.

Long Wait Times 

Many patients face long wait times when seeking help for potential ADHD or ASD. One study found the median wait time for assessment to be 525 days for children and 252 days for adults. Moreover, only 20% of child patients and 47% of adult patients were seen within the study’s proposed diagnostic time target. Long wait times not only delay care, they may also dissuade patients from seeking help in the first place. 

Reliance on Subjective Measures

Subjective diagnostic measures are limited in their diagnostic capability, since patients may or may not describe their experiences accurately. Since ASD and ADHD have overlapping symptoms, it's important to look beyond subjective accounts to ensure a well-informed diagnosis and appropriate care. While understanding a patient’s lived experience is important, so is leveraging objective measures of cognition to gain a comprehensive understanding of a patient’s symptoms. 

Cognitive Testing for Comorbid Autism and ADHD 

Digital cognitive testing from Creyos gives providers the ability to leverage objective measures of cognition while screening for subjective patient experiences in the same assessment, all in one platform. Creyos lets you customize assessments to individual patients; test for signs of ADHD and ASD concurrently with age-appropriate standardized psychological/behavioural questionnaires, and scientifically validated cognitive tests. 

Access industry-standard, age-appropriate questionnaires for ADHD, like the Adult ADHD Self-Report Screener (ASRS), the Strengths and Weaknesses of ADHD Symptoms and Normal Behavior (SWAN), and the Vanderbilt ADHD Diagnostic Rating Scale(VADRS), alongside the Autism Spectrum Quotient (AQ), for efficient and accurate subjective screening to ensure comprehensive patient assessment. For patients with ASD, patterns in intellectual function can vary from one individual to another, so cognitive testing helps identify strengths and weaknesses in a particular patient.

Not only can providers leverage custom testing protocols—they can also rely on a pre-built protocol to quickly and accurately assess for ADHD. 

The Creyos ADHD Cognitive Assessment and Report lets providers assess for ADHD in three stages: the completion of four cognitive tasks, the completion of the SART continuous performance task, and the completion of an optional age-appropriate questionnaire. This protocol acts as an assessment for symptoms and cognitive markers specific to ADHD. 

Understanding ADHD and Autism Comorbidity 

ADHD and autism may be commonly comorbid conditions, but there is still significant research to be done into how the two conditions interact. Additionally, patients may present with apparent comorbid ADHD and ASD, but overlapping symptomology makes it difficult to discern the two conditions and make appropriate clinical decisions without objective cognitive measures and a thorough understanding of both disorders. 

Objective cognitive testing can play a major role in confident clinical decision-making regarding the diagnosis and treatment of ADHD, ASD, or other concurrent neurodevelopmental conditions. Leveraging scientifically validated testing alongside subjective questionnaires gives providers the comprehensive insight they need to provide the best possible care. 

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Reviewed by Sydni Paleczny, Staff Scientist

Sydni earned her MSc in Neurosciences at Western University under Dr. Adrian Owen. Her research explores neuropsychological outcomes after cardiac surgery, with interests in cognitive neuroscience, critical care, and brain health. At Creyos, she supports scientific validity, health technology, and ongoing research.