Confusable diagnoses · PANCE / PANRE

Attention-Deficit/Hyperactivity Disorder vs Autism Spectrum Disorder

Written & clinically reviewed by Ryan Busch, PA-C · Updated August 2026 · Report an error

Attention-Deficit/Hyperactivity Disorder and Autism Spectrum Disorder are easy to mix up on the boards. Here's a side-by-side comparison — presentation, workup, imaging, and first-line treatment — drawn from our full outlines.

Attention-Deficit/Hyperactivity Disorder vs Autism Spectrum Disorder at a glance

  • Attention-Deficit/Hyperactivity Disorder: Persistent inattention and/or hyperactivity-impulsivity present before age 12 with cross-setting impairment.
  • Autism Spectrum Disorder: Persistent deficits in social communication plus restricted/repetitive behaviors present in early development.

Try two board-style questions on Attention-Deficit/Hyperactivity Disorder vs Autism Spectrum Disorder

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Question 1PsychiatryEasy
A 9-year-old boy has persistent inattention, impulsivity, and hyperactivity at school and at home. Symptoms began before age 12 and impair academic performance. Which of the following is a common complication if this disorder remains untreated?
  • AChronic tic disorder with vocal tics
  • BAcademic failure and accidental injury
  • CSelective mutism in social settings
  • DProgressive decline in intellectual ability
Reveal answer & full explanation
Correct answer: B — Academic failure and accidental injury
  • AChronic tic disorder with vocal tics
  • BAcademic failure and accidental injury✓
  • CSelective mutism in social settings
  • DProgressive decline in intellectual ability

Why Academic failure and accidental injury is correct

  • Untreated ADHD commonly leads to academic underachievement, peer and family conflict, and a higher rate of accidental injuries from impulsivity.
  • The cross-setting symptoms beginning before age 12 with functional impairment satisfy the diagnostic criteria for ADHD.
  • These functional outcomes, along with later substance-use risk, are the recognized complications of leaving it untreated.

Why the others are wrong

  • Chronic tic disorder with vocal tics — Comorbidity trap: tics frequently co-occur with ADHD and follow their own course, but they are a separate neurodevelopmental disorder rather than a consequence of untreated symptoms.
  • Selective mutism in social settings — Comorbidity trap: selective mutism is an anxiety-spectrum condition of early childhood and does not arise from untreated inattention or hyperactivity.
  • Progressive decline in intellectual ability — Wrong-trajectory trap: measured intelligence stays stable in ADHD, and the untreated child underperforms academically without any deterioration in cognitive capacity.
Question 2PsychiatryMedium
A 30-month-old boy is brought to the clinic by his parents, who are worried about his development. He has fewer than 10 spoken words, makes little eye contact, lines up his toy cars for long periods, and becomes very distressed when his daily routine changes. He was born at term after an uncomplicated pregnancy and delivery, and audiology testing is normal. Which of the following is the strongest risk factor for this child's likely condition?
  • AAn older sibling with autism
  • BAdvanced paternal age at birth
  • CMaternal obesity before pregnancy
  • DMale sex of the affected child
Reveal answer & full explanation
Correct answer: A — An older sibling with autism
  • AAn older sibling with autism✓
  • BAdvanced paternal age at birth
  • CMaternal obesity before pregnancy
  • DMale sex of the affected child

Why An older sibling with autism is correct

  • ASD is highly heritable (~80%), and a full sibling with ASD confers a recurrence risk of roughly 10-20% — by far the largest single risk factor among the options.
  • This child's social-communication deficits, lining up toys, and insistence on sameness fit ASD, and familial recurrence outweighs every other exposure listed.

Why the others are wrong

  • Advanced paternal age at birth is a real but modest contributor that raises the de novo mutation burden; the increase in risk is far smaller than that conferred by an affected sibling.
  • Maternal obesity before pregnancy has been linked to a small and inconsistent rise in neurodevelopmental risk, an effect far weaker than familial recurrence and not a leading ASD risk factor.
  • Male sex of the affected child is present here and carries a real 3-4x higher diagnostic rate in boys, but that sex difference is a much smaller effect than the 10-20% sibling recurrence risk.
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Side-by-side comparison

FeatureAttention-Deficit/Hyperactivity DisorderAutism Spectrum Disorder
At a glancePersistent inattention and/or hyperactivity-impulsivity present before age 12 with cross-setting impairment.Persistent deficits in social communication plus restricted/repetitive behaviors present in early development.
Classic presentationInattention: careless mistakes, difficulty sustaining attention, doesn't listen, fails to follow through, organization difficulties, avoids sustained mental effort, loses things, easily distracted, forgetful; Hyperactivity-impulsivity: fidgets, leaves seat, runs/climbs inappropriately, can't engage quietly, 'on the go', talks…Social communication: reduced social-emotional reciprocity, atypical nonverbal communication, difficulty developing and maintaining relationships appropriate to developmental level; Restricted/repetitive: stereotyped/repetitive motor movements or speech, insistence on sameness/routines, highly restricted fixated interests, hyper- or…
Workup / key labsDSM-5-TR: (A) >=6 inattention and/or >=6 hyperactivity-impulsivity symptoms for >=6 months in children, or >=5 for individuals age 17 and older; (B) Several symptoms present before age 12; (C) Present in >=2 settings; (D) Clear interference with functioning; (E) Not better explained by another disorder. Specify combined, predominantly…DSM-5-TR: (A) Persistent deficits in social communication and interaction across contexts — all three subcriteria (reciprocity, nonverbal communication, relationships); (B) Restricted/repetitive patterns — >=2 of four (stereotypies, insistence on sameness, restricted interests, sensory differences); (C) Symptoms in early developmental…
ImagingNot routinely indicatedMRI not routine; obtain if focal findings, atypical regression (after age 2-3, motor regression, or multiple regressions), seizures, microcephaly, or macrocephaly with neurologic signs; the typical language/social regression at 18-24 months seen in about a quarter of children with ASD does not by itself require MRI or EEG
First-line treatmentBehavioral parent training and classroom interventions — first-line in preschool age (4-5 years) and adjunct at all ages; Stimulant — methylphenidate, lisdexamfetamine, mixed amphetamine salts (first-line pharmacotherapy school-age and older); titrate to effect over weeks; methylphenidate blocks dopamine and norepinephrine reuptake…Early intensive behavioral intervention — applied behavior analysis (ABA), naturalistic developmental behavioral interventions (NDBI), Early Start Denver Model; Speech-language therapy; occupational therapy for sensory and motor issues; Educational supports — IEP, structured teaching; Family support and psychoeducation; respite care;…

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Full outlines

Attention-Deficit/Hyperactivity Disorder (ADHD) Autism Spectrum Disorder (ASD) All 514 diagnoses

Educational use only. This outline is a study aid for PA students and is not medical advice or a substitute for clinical judgment. FirstPassPA is an independent study tool and is not affiliated with, endorsed by, or sponsored by NCCPA or PAEA. PANCE® and PANRE® are registered trademarks of the National Commission on Certification of Physician Assistants; End of Rotation™ is a program of the Physician Assistant Education Association.