A clinical guide for referrers navigating overlapping presentations in young people.
ASD, ADHD, and anxiety frequently look alike in young people, particularly in the consulting room. Inattention, social withdrawal, sleep difficulty, irritability, and school avoidance can all signal any one of the three — or a combination. Clear differentiation matters because it shapes treatment, school supports, and family understanding. This guide explains our approach to differential assessment.
Up to 50–70% of autistic young people meet criteria for ADHD, and around 40% meet criteria for an anxiety disorder.
Anxiety is the most common mental health condition in Australian young people, with around 1 in 14 children aged 4–17 experiencing an anxiety disorder.
Co-occurrence is the norm rather than the exception, so the question we are often asking is not ‘which one is it’ but ‘which combination, and what is driving daily functioning right now’.
Where They Overlap
Common surface presentations that can fit all three:
Difficulty concentrating in class or completing homework.
Withdrawal from peers, group work, or social activities.
Sleep difficulty and morning resistance.
Emotional dysregulation, meltdowns, or shutdowns.
Somatic complaints (stomach aches, headaches) before school.
School refusal and avoidance behaviour.
Looking beyond the surface to the why is what separates them clinically.
Signs of ASD
Differences in social-communication that are pervasive and longstanding (not just present when anxious): reciprocity, non-verbal communication, friendship development.
Restricted or repetitive behaviours, deep interests, insistence on sameness, sensitivity to change in routine.
Sensory processing differences across multiple modalities.
Early developmental signs (language profile, play, pretend skills, joint attention).
Difficulty that persists across settings and across mood states.
Signs of ADHD
Inattention, distractibility, and forgetfulness present from early childhood and across multiple settings.
Hyperactivity or restlessness (more obvious in childhood; often internalised in adolescent girls and adults).
Impulsivity in speech, decision-making, or peer interactions.
Executive function difficulties: starting tasks, time management, working memory, emotional regulation.
Family history of ADHD, and a positive response (in retrospect) to high-structure or high-interest environments.
Signs of Anxiety
Worry that is excessive, hard to control, and out of proportion to the situation.
Avoidance that follows a clear stress-relief pattern — the young person feels better immediately after avoiding.
Reassurance-seeking, perfectionism, and a strong need for certainty.
Physical symptoms that intensify before feared situations and ease afterwards.
Symptoms that worsen during transitions and exam periods, and ease during holidays.
A useful clinical question: does the difficulty look the same on a Tuesday afternoon at home with one safe person as it does on a Monday morning in a busy classroom? ADHD and ASD presentations are typically pervasive across contexts. Anxiety presentations are typically context-driven.
Our Assessment Approach
Our assessment helps clarify what is driving the young person’s difficulties:
We take a detailed developmental history across childhood and adolescence.
We use rating scales from several sources to screen for ASD, ADHD, anxiety, depression, and trauma.
We use direct observation, including the ADOS-2, when ASD is being considered.
We assess thinking and learning when attention, executive function, or learning concerns are present.
We consider trauma, sleep, and family context before finalising a diagnosis.
We provide a clear formulation, with the main concern, any co-occurring conditions, and practical next steps.
Referral Pathways
If anxiety appears primary
Start with therapy, such as CBT, ACT, or exposure-based work. Treatment may reduce anxiety enough to show whether ASD or ADHD features are still present. We can begin therapy and review the need for assessment later.
If ASD or ADHD appears primary or strongly suspected
Formal assessment can clarify the picture before treatment begins. A diagnosis may also support NDIS access, school adjustments, and family understanding.
If you are not sure
Please call us. A short clinician-to-clinician conversation can reduce uncertainty and help match the young person to the right pathway.
HELPFUL RESOURCES
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Australian centre for child mental health. Free online learning for GPs and paediatricians on child mental health differentials.
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Evidence-based parenting information across neurodevelopmental and mental health topics.
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Mental health information, including anxiety and depression in young people.
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Australian Evidence-Based Clinical Practice Guideline for ADHD (2022).
