Differentiating ASD and ADHD: Diagnostic Considerations

Introduction to Diagnostic Challenges

The American Academy of Pediatrics recommends screening for ADHD symptoms in every child with ASD, as approximately 50% of individuals with ASD meet criteria for ADHD 1

Individuals with pure ASD typically show consistent difficulty engaging with tasks outside their narrow, restricted interests, regardless of task novelty or interest level, which is attributed to fundamental social-communication deficits and insistence on sameness 2
In contrast, individuals with ASD+ADHD exhibit variable engagement patterns, hyperfocusing on interesting tasks but struggling with non-interesting ones, suggesting comorbid ADHD 1

The presence of ADHD-specific features such as fidgeting, motor restlessness, impulsivity-driven behaviors, and response to structure can indicate comorbidity in individuals with ASD 1
ASD repetitive behaviors, such as hand flapping or finger flicking, serve self-regulatory functions and increase with stress or excitement, whereas ADHD motor behaviors are driven by impulsivity and hyperactivity 1

The ADOS-2 remains the gold standard for identifying core ASD features, with a focus on social-communication items that differentiate ASD from ADHD, such as joint attention deficits and impaired conventional gestures 1
Critical items that distinguish ASD from ADHD alone include failure to point for interest, absence of conventional gestures, use of others' bodies as tools, and qualitatively impaired eye contact 1

Diagnostic overshadowing, where all symptoms are attributed to the more noticeable ASD diagnosis, is a common pitfall that can lead to missed comorbid ADHD, emphasizing the need for systematic screening for ADHD symptoms in individuals with ASD 3, 4
Individuals with ASD+ADHD are more severely impaired than those with ASD alone, with greater deficits in social processing, adaptive functioning, executive control, and motor problems, highlighting the importance of accurate diagnosis and treatment 1