Autism Spectrum Disorder and Attention-Deficit/Hyperactivity Disorder Overlap and Comorbidity in Adults

Autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD) frequently co-occur in adulthood, creating a clinical profile that differs meaningfully from either condition alone. Evidence indicates that impulsivity and attentional inconsistency characteristic of ADHD interact with the rigidity, sensory sensitivities, and social-cognitive differences associated with ASD, amplifying executive, emotional, and social-communication difficulties. Assessment in adults remains challenging due to reliance on child-normed instruments, symptom masking, and overlapping phenomenology, underscoring the importance of nuanced clinical judgment. Treatment is most effective when integrated, combining cautious stimulant use when indicated, targeted nonstimulants, cognitive-behavioral therapy adapted to autistic cognition, executive-function coaching, and environmental modifications across work and home contexts. Finally, key research gaps are highlighted, including the need for adult-specific diagnostic tools, greater attention to sex and gender differences, and clinical trials designed specifically for comorbid presentations to improve long-term functional outcomes and quality of life.