ADHD and Autism: How to Tell the Difference (2026)

If you've been told you might have ADHD, or autism, or both — and you're not sure which one fits — you're in good company. These two conditions look remarkably similar on the surface, and they're frequently confused even by clinicians. Both affect executive function, sensory processing, social interaction, and emotional regulation. Both start in childhood. And importantly, you can have both at once.

The confusion runs in both directions. People with autism are often initially diagnosed with ADHD because their attention difficulties are more visible than their social communication differences. People with ADHD are sometimes misidentified as autistic because their social difficulties (driven by inattention and impulsivity) look similar to autistic social communication patterns on the surface.

This diagnostic confusion has real consequences. The wrong diagnosis leads to the wrong treatment. A person with unrecognised autism who is treated only for ADHD may find that stimulant medication improves their focus but does nothing for sensory overwhelm, social exhaustion, or need for routine. A person with unrecognised ADHD who receives only autism supports may develop excellent routines and structures but still struggle with initiation, sustained attention, and impulse control.

The AADPA Clinical Practice Guide (2022) acknowledges this overlap and recommends that clinicians conducting ADHD assessments should consider whether autism may also be present, and vice versa. The RANZCP similarly recognises the importance of differential diagnosis between the two conditions.

Understanding the key differences — and importantly, where they overlap — is essential for getting an accurate diagnosis and effective support.

While ADHD and autism share surface-level similarities, the underlying mechanisms and patterns differ in important ways:

• Social interaction:**
• ADHD: Typically wants social connection but struggles to maintain it. May interrupt conversations (impulsivity), miss social cues (inattention), forget to reply to messages, or overshare. The desire for connection is usually strong.
• Autism: May have fundamentally different social processing — not necessarily less interest in people, but a different way of understanding and navigating social dynamics. May prefer fewer, deeper relationships. Social exhaustion comes from the processing effort, not from inattention.

• Routine and change:**
• ADHD: Generally resists routine. Finds sameness boring. Craves novelty, spontaneity, and stimulation. May start many projects but finish few.
• Autism: Generally needs routine and predictability. Becomes distressed by unexpected changes. Finds comfort in sameness and repetition. May have intense, sustained interests.

• Attention patterns:**
• ADHD: Difficulty sustaining attention across the board, except during hyperfocus (which is driven by interest/novelty rather than importance). Attention is inconsistent and context-dependent.
• Autism: Can sustain deep, focused attention on areas of intense interest for extended periods. This looks like "hyperfocus" but is more accurately described as a deep, sustained special interest. Attention difficulties are more related to switching between tasks or attending to things outside areas of interest.

• Sensory processing:**
• ADHD: Often sensory-seeking — needs background noise, movement, or fidgeting to maintain focus. Under-stimulation is the core problem.
• Autism: Often sensory-avoidant — overwhelmed by bright lights, loud noises, certain textures, or strong smells. Over-stimulation is the core problem. Some autistic people are also sensory-seeking in specific modalities.

• Emotional regulation:**
• ADHD: Emotional reactions are often fast, intense, and short-lived. Rejection sensitivity is common. Frustration tolerance is low. Emotions shift rapidly.
• Autism: Emotional reactions may be intense but slower to build and slower to resolve. Meltdowns (from sensory or cognitive overload) differ from ADHD emotional impulsivity. Alexithymia (difficulty identifying emotions) is more common in autism.

Despite the differences outlined above, there are genuine areas of overlap that make differential diagnosis challenging even for experienced clinicians:

Executive function difficulties: Both ADHD and autism involve executive function challenges, but the profile differs. ADHD executive dysfunction centres on initiation (can't start tasks), sustained attention (can't maintain focus), and working memory (forgets what they were doing). Autistic executive dysfunction centres more on cognitive flexibility (difficulty switching between tasks or perspectives), planning (difficulty organising multi-step processes), and generalisation (difficulty applying skills from one context to another). In practice, both presentations lead to difficulty with organisation, time management, and completing tasks — making the underlying cause hard to distinguish without careful assessment.

Stimming and fidgeting: Both ADHD and autistic people engage in repetitive movements, but for different reasons. ADHD fidgeting is typically about increasing stimulation — tapping a pen, bouncing a leg, clicking a button — to maintain alertness and focus. Autistic stimming serves a broader range of functions including self-regulation (managing emotions or sensory input), communication (expressing excitement or distress), and comfort (rocking, hand-flapping). The distinction is in the function, not the behaviour.

Sensory sensitivity: Research suggests that up to 70% of people with ADHD report atypical sensory processing, as do the vast majority of autistic people. Sensory issues were historically considered unique to autism, but are now recognised in ADHD as well. The pattern tends to differ (ADHD = more seeking; autism = more avoidance), but there is significant individual variation.

Social difficulties: Both conditions can result in social challenges — missed cues, difficulty maintaining friendships, social rejection. The mechanisms differ (ADHD = inattention and impulsivity; autism = different social processing), but the lived experience of social difficulty is similar.

Emotional dysregulation: Both ADHD and autism involve difficulty regulating emotions. Rejection Sensitive Dysphoria (RSD) is commonly described in ADHD. Autistic meltdowns and shutdowns reflect emotional overwhelm. Both can look like "overreacting" to observers.

Sleep difficulties: Both conditions are associated with disrupted sleep — difficulty falling asleep, irregular sleep-wake cycles, and non-restorative sleep are reported in both ADHD and autism.

Yes. Since the DSM-5 (2013), ADHD and autism can be diagnosed in the same person. This is not rare — it is common. Research consistently finds that 50–70% of autistic people also have ADHD, and 20–50% of people with ADHD meet criteria for autism.

The co-occurrence of both conditions is often called AuDHD in community spaces. It is not a separate diagnosis — it is two distinct diagnoses in one person. But the lived experience of having both is qualitatively different from having either alone, because the conditions interact in complex ways.

• For example, a person with AuDHD might:
• Crave routine (autism) but be unable to maintain it (ADHD)
• Want social connection (ADHD) but find it exhausting (autism)
• Need quiet to avoid sensory overwhelm (autism) but need stimulation to focus (ADHD)
• Start many special interests enthusiastically (ADHD novelty-seeking) then maintain some with intense depth (autism)

Implications for treatment: Having both conditions means that treatment for one must account for the other. Stimulant medication for ADHD may increase sensory sensitivity (an autism-related concern). Autism-focused strategies that rely on rigid routines may not work for someone whose ADHD makes routine maintenance difficult. The most effective approaches are flexible and integrate understanding of both conditions.

If you think you might have both: We have a detailed companion guide that covers AuDHD in depth: AuDHD: When You Have Both ADHD and Autism. It covers assessment pathways, treatment considerations, NDIS implications, and how to find a provider experienced with dual diagnosis.

Differential diagnosis between ADHD and autism requires a comprehensive assessment that goes beyond symptom checklists. Experienced clinicians use a combination of clinical interview, standardised tools, developmental history, and direct observation.

• Assessment tools for ADHD:**
• DIVA-5 (Diagnostic Interview for ADHD in Adults) — structured interview covering current and childhood symptoms
• CAARS (Conners' Adult ADHD Rating Scales) — self-report and observer-report questionnaires
• ASRS (Adult ADHD Self-Report Scale) — screening tool developed by the WHO
• QB Test — computerised test measuring attention, impulsivity, and activity (used by some Australian clinics)

• Assessment tools for autism:**
• ADOS-2 (Autism Diagnostic Observation Schedule) — gold-standard observational assessment
• ADI-R (Autism Diagnostic Interview-Revised) — structured developmental history interview
• AQ-50/AQ-10 (Autism Quotient) — screening questionnaires
• RAADS-R (Ritvo Autism Asperger Diagnostic Scale-Revised) — self-report screening for adults

What a thorough differential assessment includes:

• Detailed developmental history — ADHD and autism are both present from childhood, but the developmental trajectory differs. Early language development, social play patterns, and sensory behaviours in infancy/toddlerhood can help distinguish the conditions.
• Contextual analysis of symptoms — Is the social difficulty driven by inattention (ADHD) or by different social processing (autism)? Is the rigidity about anxiety/overwhelm (autism) or about hyperfocus/interest (ADHD)?
• Assessment across multiple settings — both conditions should be evident in more than one context (home, work, social). Informant reports (from partners, parents, or close friends) add valuable perspective.
• Consideration of masking — particularly important for women, who may present very differently from textbook descriptions of both conditions.
• Screening for the other condition — the AADPA guideline recommends that any ADHD assessment should consider autism, and vice versa.

The importance of getting it right: An accurate diagnosis guides effective treatment. Stimulant medication helps ADHD but does not address core autism traits. Autism-focused therapy helps autistic people but does not address ADHD executive dysfunction. If both conditions are present, both need to be identified and addressed.

If you are unsure whether your difficulties are better explained by ADHD, autism, or both, the assessment pathway you choose matters:

Recommended approach:

• Start with your GP — discuss your concerns and ask for a referral. Mention that you want an assessment that considers both ADHD and autism. In Queensland and South Australia, GPs can now diagnose ADHD directly (see our GP ADHD diagnosis guide).

• Choose a clinician experienced with both conditions — this is the single most important factor. A clinician who only assesses for one condition may miss the other. Look for providers who explicitly list both ADHD and autism in their clinical experience.

• Consider a neuropsychological assessment — a comprehensive neuropsych assessment (conducted by a clinical psychologist or neuropsychologist) tests cognitive functioning across multiple domains and can help distinguish ADHD, autism, and other conditions that affect executive function and social cognition. These assessments are thorough but expensive ($1,500–$3,000+).

• Prepare thoroughly — bring school reports, developmental history, and examples of current difficulties. If possible, have a parent or partner attend part of the assessment to provide informant history. The more information the clinician has, the more accurate the diagnosis.

What to watch out for:

• Clinicians who say "you can't have both" — this is based on outdated DSM-IV criteria and is simply wrong under current diagnostic standards
• Very brief assessments — a 20-minute screening cannot adequately distinguish ADHD from autism. Comprehensive assessment typically takes 2–4 hours across one or more sessions.
• Over-reliance on a single tool — diagnosis should not rest on one questionnaire score. Multiple sources of information are needed.
• Dismissal based on stereotypes — "You make eye contact, so you're not autistic" or "You did well in school, so you don't have ADHD" are not valid clinical reasoning.

Use our directory to search for providers experienced with both ADHD and autism assessment. We currently list 1000 ADHD providers across Australia. Filter by your state and check that the provider lists experience with both conditions before booking.