Beyond the Overlap: How Cognitive Markers Help Differentiate ADHD from Autism Spectrum Disorder

Attention Deficit/Hyperactivity Disorder (ADHD) and Autism Spectrum Disorder (ASD) are two neurodevelopmental conditions that frequently overlap in outward behavior, making accurate differentiation difficult in educational and clinical settings. ADHD is commonly associated with inattention, impulsivity, hyperactivity, and response inhibition difficulties, while ASD is more strongly associated with social communication differences, restricted or repetitive behaviors, sensory differences, and difficulty with flexibility (NIMH, 2024; CDC, 2025). However, symptoms such as distractibility, poor task completion, emotional dysregulation, and social difficulty can appear in both conditions, which means diagnosis cannot rely on one visible behavior alone. This paper examines the research question: What cognitive markers most reliably distinguish ADHD symptoms from overlapping traits in individuals with Autism Spectrum Disorder? The study uses a mixed review-based and survey-based methodology. Secondary research was collected from clinical and peer-reviewed sources on ADHD-ASD overlap, executive functioning, response inhibition, attention regulation, social reciprocity, theory of mind, and cognitive flexibility. Primary data was collected through a Google Form designed for professionals such as clinicians, therapists, psychiatrists, educators, and behavior specialists. The form specifically examined markers including attention regulation, impulsivity, executive functioning, working memory, processing speed, cognitive flexibility, response inhibition, social communication, and repetitive behavior. The survey received 19 professional responses. Therapists formed the largest respondent group at 63.2%, and 73.7% of respondents reported more than ten years of experience. The strongest ASD-leaning findings were social disengagement, where 78.9% agreed or strongly agreed that it is more prevalent in ASD, and repetitive behaviors, where 63.1% agreed or strongly agreed that they are more common in ASD. The strongest ADHD-leaning finding was hyperactivity/impulsivity, where 52.7% agreed or strongly agreed that it is more common in ADHD. However, responses on inattention were mixed: 42.1% agreed or strongly agreed that inattention is more common in ADHD, while 47.4% disagreed or strongly disagreed, suggesting that inattention alone is not a reliable differentiating marker. In the multiple-choice section, the most useful differentiator was eye contact and social reciprocity, selected by 63.2% of respondents, followed by social communication patterns and impulsivity, each selected by 47.4%. Clinical observation was the most commonly used assessment method, selected by 84.2% of respondents. The findings suggest that no single cognitive marker can fully separate ADHD from ASD. Instead, the most reliable distinction comes from a profile-based model: ADHD aligns more strongly with impulsive responding, poor response inhibition, scattered attention, and inconsistent task persistence, while ASD aligns more strongly with social-pragmatic difficulty, nonverbal communication differences, restricted interests, repetitive behavior, sensory sensitivities, and rigidity. This paper concludes that ADHD-ASD differentiation should focus on the cause and pattern behind behaviors rather than the behavior alone.