ADHD or Autism? How to Differentiate Between the Two in Clinical Assessments
- Amanda Moses Psychology
- Mar 20
- 5 min read
Updated: Mar 26
Why ADHD and Autism Are Frequently Confused in Clinical Assessments
Autism and ADHD have historically been frequently misdiagnosed or missed. Many clinicians state that they are confused due to what appears to be overlapping traits between these two neurotypes and other mental health conditions that frequently co-occur with them. Many individuals, particularly adults and women or AFAB individuals, go undiagnosed or receive incorrect diagnoses due to a lack of nuanced understanding among clinicians.
For psychologists looking to improve their diagnostic accuracy, ADHD and autism assessment training is essential. Differentiating between the two requires a deep understanding of their similarities, differences, and best assessment practices.
Overlapping Traits of ADHD and Autism?
ADHD and autism have traits that seem to confuse many clinicians when teasing them apart. Some key themes include:
Social differences – Is difficulty maintaining conversations, misreading social cues, or feeling out of sync with peers an autistic experience or an ADHD one?
Executive functioning difficulties – Problems with planning, organisation, impulse control, and working memory. Which of these are attributed to autism or ADHD?
Sensory sensitivities – Hypersensitivity to noise, light, or textures, sensory-seeking behaviours, or being distracted in environments with overwhelming sensory input.
Hyperfocus and intense interests – Deep engagement in topics of interest— is this an autistic trait, an ADHD trait, or both?
Difficulties with transitions and routine disruptions – How much of this is due to autism or ADHD?
These traits can make it difficult for clinicians to determine which diagnosis is most appropriate—or whether both are present.
Key Differences Between ADHD and Autism
ADHD and autism have core differences that clinicians should be aware of. While they frequently co-occur, most people experience these traits as distinct or polarising:
Feature | ADHD | Autism |
Social Differences | Impulsive social interactions, difficulty with turn-taking in conversations, excessive talking, interrupting others | Challenges with reciprocity in conversations and difficulty understanding neurotypical social norms and rules, preference for interacting through interests |
Attention & Focus | Difficulty sustaining attention unless highly interested, easily distracted | Can focus for long periods, especially on special interests |
Routine & Flexibility | Struggles with organisation and time management | Prefers routines and consistency, struggles with unexpected changes |
Sensory Processing | Is distractible in loud or busy environments, may need movement to regulate hyperactivity, however, this is not the same as being hypo or hyper sensitive to sensory stimuli | Can be sensory-seeking or avoidant, experiences sensory information differently than neurotypical people, which can cause distress |
Communication Style | May talk excessively or shift topics quickly, may struggle with regulating attention in conversations, interrupting or finishing others sentences | Prefers structured conversations that have a clear point or are about a topic of interest, may take longer to process verbal information, can struggle with "small talk" |
Special Interests | Many shifting interests, novelty-seeking, can become quickly fascinated by an interest and then lose interest due to novelty wearing off | Deep, long-term special interests, may collect extensive knowledge on a topic |
Best Assessment Strategies for Differentiating ADHD and Autism
A comprehensive assessment approach is essential to accurately distinguish between ADHD and autism. It’s also important to understand that many individuals meet criteria for both, which can create diagnostic overshadowing due to the polarising nature of some traits. To accurately assess and diagnose autism, ADHD, or AuDHD, a clinician must understand which traits stem from which neurotype. They must also fully understand what an AuDHD (combined autism and ADHD) presentation looks like—especially when compared to a single neurotype presentation.
Psychologists should integrate multiple assessment tools, including:
A detailed clinical interview exploring developmental history, social interactions, and behavioural patterns is essential. Key considerations include:
Early childhood development – Autistic and ADHD traits are often present from early life; however, they may not become apparent until demands exceed capacity to cope.
Social history – Autistic individuals often struggle with peer relationships from an early age, whereas ADHDers may be overly social but struggle with impulsivity in those interactions.
Executive function challenges – Autistic individuals may experience more difficulty with transitions and rigid thinking, while ADHDers tend to struggle with sustaining attention, organisation, task completion, and impulsivity.
My new intake questionnaires are designed to support this stage of assessment by streamlining the collection of developmental history, behavioural patterns, and executive functioning difficulties—helping you gather the right data from the outset.
2. Diagnostic Interviews and Questionnaires
Utilising standardised diagnostic tools can improve accuracy.
For ADHD:
DIVA-5 (Diagnostic Interview for ADHD in Adults) – Covered in my ADHD assessment training
For Autism:
MIGDAS-2 (qualitative, strength-based autism assessment) – Included in my autism assessment training
3. Executive Function and Sensory Assessments
ADHD assessments should focus on aspects of executive functioning like impulse control, attention regulation, and working memory, using tools such as:
BRIEF (Behaviour Rating Inventory of Executive Function)
Autism assessments should explore sensory profiles and cognitive flexibility, using tools such as:
SPM-2 (Sensory Processing Measure-2)
In-depth qualitative interviews
I provide training on all of these screeners—and more—in my diagnostic assessment training.
Common Misdiagnoses and Diagnostic Pitfalls
Due to diagnostic overshadowing when both neurotypes are present, and a general misunderstanding of how traits may intersect, individuals are frequently misdiagnosed—especially when clinicians fail to consider both autism and ADHD in their diagnostic formulation.
Statistically, individuals are far more likely to meet criteria for both ADHD and autism than for just one of these neurotypes in isolation. Yet professionals often hesitate to diagnose both. In some cases, this happens because they are only exploring one possibility rather than considering both.
Given the high co-occurrence between these neurotypes, every good autism or ADHD assessment should include consideration for the other. This is exactly why, in my ADHD and autism assessment training,, I teach both together—and help clinicians recognise the unique AuDHD profile. Understanding autism, ADHD, and the blended AuDHD presentation is essential for accurate identification.
Why Psychologists Need ADHD and Autism Assessment Training
To confidently differentiate between ADHD and autism, psychologists need specialised training in neurodivergent assessment. My ADHD and autism assessment training provides:
In-depth guidance on using diagnostic tools like the DIVA-5 and MIGDAS-2
Case studies to illustrate complex presentations and masking behaviours
Strategies for identifying co-occurring conditions and avoiding misdiagnosis
Demonstration videos included for MIGDAS-2 and DIVA-5 assessments
Final Thoughts
Differentiating between ADHD and autism requires more than just symptom checklists—it demands a holistic, neurodiversity-affirming approach that considers developmental history, individual experiences, and executive functioning.
For psychologists looking to refine their diagnostic skills, my ADHD and autism assessment training offers practical tools and clinical insight to build confidence and improve diagnostic accuracy.
Interested in advancing your skills in ADHD and autism assessment? Explore my ADHD and autism assessment training and gain the tools you need for accurate, affirming diagnoses.