AuDHD
ADHD and autism are both neurodevelopmental conditions involving distributed brain networks; however,
ADHD is primarily characterised by dysregulation of attention, inhibition, and motivation systems.
Autism is characterised by differences in sensory integration, social cognition, and predictive processing networks.
Overlap may occur, particularly in executive functioning, but the underlying neural mechanisms differ.
✨At RMC we view Autism and ADHD as differences not disorders ✨
*Research shows that 60–70% of autistic people also have ADHD.
Embrace Autism website has articles on AuDHD
AuDHD is an unofficial but popular term used to describe individuals who are Autistic and ADHD. This means that an AuDHDer has been self/formally diagnosed with autism and ADHD because they have traits characteristic of both conditions.
AuDHD is a colloquial term, but it does not exist as an official diagnosis. This means that an AuDHDer who has a formal diagnosis will have documents listing both conditions separately; it will likely say that they have ADHD and autism.
The diagnostic criteria conceptualise ADHD as an attentional deficit. However, ADHDers are perhaps better described as having a form of hyper-attention.
ADHDers experience all stimuli at once and these stimuli all fight for our attention, making it difficult to attend to any one thing.
The exception is when we are absorbed in something interesting. In this case, ADHDers experience hyperfocus just like autistics do.
*The Prevalence of Attention Deficit/Hyperactivity Disorder Symptoms in Children and Adolescents With Autism Spectrum Disorder Without Intellectual Disability: A Systematic Review (Eaten et al., 2023)
What is AuDHD
There is a strong link between autism and ADHD, with both having high heritability
and genetic overlap.
Common traits shared in ADHD and autism include:
Sensory differences, Executive dysfunction, Hyperfocus and intense interests.
Rejection sensitivity, Social challenges, Sleep problems.
Differences in eye contact, Difficulties with interoception, such as noticing when you are hungry.
Although there are many similarities, differences exist; ADHD individuals may crave novelty and exhibit impulsivity, while autistic people often seek routine and similarity.
If someone is autistic and has ADHD, which some people refer to as AuDHD, they may experience an internal struggle between these contrasting traits.
An AuDHD person is likely to experience a heightened version of the shared autism and ADHD characteristics, such as an intense focus on hobbies and interests, or experience challenges socialising with neurotypical people.
- Someone with ADHD is more likely to seek out novelty and make more impulsive decisions, whereas an autistic person is more likely to crave routine and structure.
- If someone is autistic and has ADHD, known as AuDHD, they may experience an internal struggle between their competing autistic and ADHD traits and a heightened experience of shared traits.
Explaining Autism
Neuroimaging research indicates that autism is associated with differences in the development and connectivity of multiple brain regions involved in;
- social cognition
- sensory processing
- emotional regulation
- executive functioning.
These differences reflect a neurodevelopmental variation in brain organisation rather than focal pathology.
There are many clinicians who explain Autism from a Differences perspective.
Autism is usually written in deficit-based context and pathological in nature.
Clinical definition:
Autism is characterised by persistent difficulties in communication and social interactions and restricted, repetitive patterns of behaviour, interests or activities.
Neurodivergent Insights website written and created by the exceptional Dr. Megan Anna Neff
explains Autism in a visual way.
Reframing Autism website has extensive resources and help explanations
Autism podcast & featuring detailed website on female presentation of Autism by Dr Henderson
Embrace Autism website
All the key Autism self report assessments can be accessed and results given
immediately. Helpful perspectives on Autistic strengths.
From the authors: “Dissatisfied with the lack of information available on autism in adults, in 2018 we founded Embrace Autism, which we intended as a platform to distribute research and experience-based information on autism. We did this as a way to empower ourselves and fellow autistics. Because for many of us, we don’t come to fully understand and appreciate ourselves until we find out that we are autistic”.
Autism Awareness Australia website
Why Sensory Overstimulation Happens in Autism
Many autistic adults experience sensory overstimulation. This does not mean being “too sensitive” or not coping well. It reflects differences in how the brain processes information.
Your brain is constantly receiving input — sounds, lights, movement, touch, smells, conversations, internal thoughts. In most people, the brain automatically filters out background information so only what is important reaches conscious awareness.
In autism, this filtering system can work differently.
1. More information gets through
The brain has a “gatekeeper” system that usually dampens background noise. In autism, this filter can be less efficient. This means more information reaches awareness at once — conversations, fluorescent lights, air-conditioning hum, clothing textures — all at similar intensity.
Instead of fading into the background, everything arrives together.
2. The brain’s volume control works differently
Brain cells communicate using signals that either turn activity up (like an accelerator) or turn it down (like a brake). In autism, the “brake” system may not dampen signals as strongly. As a result, ordinary sensory input can feel amplified — brighter, louder, sharper, or more intrusive.
It’s similar to a sound system where the volume limiter is weaker. The input itself hasn’t changed, but it feels more intense.
3. The nervous system reacts quickly
When the brain receives strong or confusing input, it may tag it as important or urgent. This can activate the body’s stress response, even when there is no real danger. The experience can feel like rising anxiety, irritability, panic, or a strong urge to escape.
This is a nervous system reaction, not a conscious decision.
4. Executive functioning can temporarily “drop offline”
The front part of the brain helps with regulating emotions, planning, speaking clearly, and staying organised. When sensory load becomes too high, this system becomes overloaded.
That is why during overstimulation you might:
- Struggle to find words
- Feel emotionally flooded
- Shut down and withdraw
- Or experience a meltdown
This is not behavioural weakness — it is cognitive overload.
5. Recovery can take time
After overload, the nervous system may stay sensitised for a while. This is why overstimulation can build up across a day or week, especially if there are few opportunities to decompress.
Masking (actively monitoring and controlling behaviour in social situations) also uses a lot of mental energy. It reduces the brain’s reserve capacity, meaning overload can happen sooner and recovery may take longer.
Sensitivity to ADHD medication
There is evidence that, in some clients with co-occurring Autism Spectrum Disorder and ADHD (AuDHD), the autistic neurobiological profile may increase sensitivity to stimulant medication side effects.
Reported effects can include increased irritability, mood lability, or anxiety; appetite suppression (with greater impact in those with sensory-based feeding challenges); sleep disturbance; exacerbation of repetitive or stereotyped behaviours in some individuals; and increased risk of sensory overstimulation due to amplification of underlying hypersensitivity.
Our clinic has extensive experience supporting AuDHD clients to initiate and adjust ADHD medication over a slower and longer titration period, allowing for careful dose optimisation while minimising destabilisation and overload risk.
Overstimulation in autistic adults reflects neurobiological differences in how the brain filters, amplifies, integrates, and recovers from input. It is not a failure of coping or emotional control; it is a systems-level load problem.
1. Reduced sensory filtering (thalamocortical gating)
The thalamus functions as the brain’s sensory “gatekeeper,” filtering and prioritising incoming sensory information before transmission to cortical regions. In many autistic adults, sensory gating is less efficient, allowing excessive, unprioritised background input (noise, light, movement) to reach the cortex.
As a result, information that is automatically filtered in others must be consciously processed. This rapidly consumes cognitive resources and contributes to baseline sensory overload. Environments may feel persistently intense, busy, and exhausting, even in the absence of psychological stress.
2. Excitation–inhibition imbalance (sensory amplification)
Neural signalling depends on a balance between excitatory activity (primarily glutamate) and inhibitory modulation (primarily GABA). Excitatory signals increase neural activity — essentially telling the next neuron to “turn up” or respond more strongly. Inhibitory signals act as the brake system, dampening activity and preventing excessive amplification.
In most brains, these systems operate in dynamic balance:
- Excitatory signals function like an accelerator.
- Inhibitory signals function like a brake.
In autism, evidence suggests reduced inhibitory modulation within key cortical circuits, meaning the “brake system” may be less efficient. When inhibition is reduced, excitatory signals have a greater impact, and sensory information can feel amplified.
Key cortical circuits involved include:
- Primary sensory cortices (auditory, visual, somatosensory), which process raw sensory input.
- Association cortices (e.g., posterior parietal and temporal regions), which integrate multisensory information.
- Prefrontal regulatory circuits, which provide top-down modulation of attention and emotional responses.
- Corticocortical and thalamocortical loops, which coordinate signal amplification and suppression across networks.
When inhibitory control in these circuits is reduced:
- Sensory signals are less effectively dampened.
- Neural “volume control” is limited.
- Habituation (getting used to stimuli) is slower or absent.
A helpful analogy is a sound system: excitatory signals are the volume knob turning up, and inhibitory signals are the automatic limiter preventing distortion. If the limiter is weaker, even ordinary input can sound amplified.
Clinically, this means sounds, lights, textures, and movement may feel sharper, louder, or more intrusive. Sensory input accumulates rather than fading into the background, increasing the likelihood of overload.
3. Hyper-reactive salience and threat detection (amygdala & salience network)
The amygdala and salience networks evaluate the emotional and behavioural relevance of incoming stimuli. In autistic adults, ambiguous or intense sensory input may be tagged as highly salient or potentially threatening.
This drives autonomic arousal via sympathetic nervous system activation. Clinically, overstimulation may be experienced as anxiety, irritability, urgency, panic, or a strong need to escape, even when no objective danger is present.
4. Prefrontal cortex overload (executive collapse)
The prefrontal cortex (PFC) governs attention allocation, emotional regulation, behavioural inhibition, planning, and the cognitive demands of masking and social monitoring.
When sensory and emotional input exceeds capacity, PFC resources are diverted toward basic regulation. Executive functions deteriorate: speech may reduce, planning and organisation decline, impulse control weakens, and emotional regulation becomes impaired.
Clinically, this produces either shutdown (withdrawal, mutism, reduced responsiveness) or meltdown (acute behavioural dysregulation and loss of control).
5. Network inefficiency and slower recovery (large-scale connectivity)
Autistic brains often demonstrate differences in long-range connectivity and increased local processing demand, resulting in greater metabolic cost for everyday tasks.
Following overload, neural recovery may be slower and sensory thresholds may remain lowered. This explains cumulative overload across a day or week and increased vulnerability during periods of fatigue or burnout.
6. The cost of masking (PFC-driven load)
Masking requires sustained top-down prefrontal activation to monitor social cues, suppress natural responses, and translate internal experiences into socially acceptable behaviour.
Neurologically, this raises baseline cortical load, reduces reserve capacity, and lowers
the threshold for overstimulation. Masking does not prevent overload; rather, it brings it closer and may prolong recovery once overload occurs.
Putting it together
Overstimulation occurs when:
- Excessive input enters the system
- Sensory filtering is reduced
- Input is amplified and fails to habituate
- Stimuli are tagged as urgent or threatening
- Executive regulatory capacity is exhausted
- Recovery mechanisms are slower and reserve is depleted
The outcome is a neurological overload state. It represents a threshold phenomenon within interconnected neural systems, not a psychological choice or deficit in effort.
Autism Tests
Camouflaging Autistic Traits Questionnaire
Clinical Interpretation Principles
A higher CAT-Q score may:
- Support an autism formulation when aligned with:
- Developmental history
- Social communication differences
- Sensory profile
- Restricted/repetitive patterns
- Be particularly informative in:
- Late-identified adults
- Women and gender diverse individuals
- High-masking presentations
A lower score does not rule out autism, particularly in:
- Individuals with limited social exposure
- Individuals with reduced insight into camouflaging
- Those with burnout or decompensation
Important Caveats
- CAT-Q measures camouflaging behaviour, not core autistic traits.
- High scores can also occur in:
- Social anxiety disorder
- Trauma-related adaptation
- High rejection sensitivity
- Chronic impression management tendencies
It should be interpreted within a full neurodevelopmental assessment framework, not in isolation.
25 Questions.
The CAT-Q measures camouflaging in general, as well as three subcategories:
1. Compensation — Strategies used to actively compensate for difficulties in social situations.
Examples: copying body language and facial expressions, learning social cues from movies and books.
2. Masking — Strategies used to hide autistic characteristics or portray a non-autistic persona.
Examples: adjusting face and body to appear confident and/or relaxed, forcing eye contact.
3. Assimilation — Strategies used to try to fit in with others in social situations.
Examples: Putting on an act, avoiding or forcing interactions with others
It may be used to identify autistic individuals who do not currently meet diagnostic criteria due to their ability to mask their autism.
Social camouflaging is defined as the use of strategies by autistic people to minimise the visibility of their autism during social situations. Social camouflaging encompasses an explicit effort to ‘mask’ or ‘compensate’ for autistic characteristics; and to use conscious or unconscious techniques which result in a less autistic behavioural presentation article
Ritvo Autism Asperger Diagnostic Scale–Revised (RAADS‑R)
80 Questions.
This is a validated instrument that helps identify autism in adults by examining lifelong patterns of cognition, perception, and behaviour. It’s especially helpful for those who relate to autistic traits but were not recognised due to masking, gender bias, or late-identified neurodivergence. It is designed to uncover developmental, social, sensory, and communication traits that may indicate autism, especially in adults who were missed or misdiagnosed earlier in life.
The Autism Spectrum Quotient (AQ) is a self-administered questionnaire used to measure autistic traits in adults (age 16+). 50 questions. The AQ measures 5 areas often associated with autism spectrum conditions:
- Social Skill – comfort and ability in social situations.
- Attention Switching – flexibility in shifting attention.
- Attention to Detail – preference for and noticing of small details.
- Communication – ease of verbal interaction.
- Imagination – ability to imagine and empathize with others.
Psychologists with experience in AuDHD
While we do not offer Autism Spectrum Disorder assessments at our clinic, we highly recommend the following professionals known for their expertise and compassionate approach in this area:
Tabitha Frew, Clinical Psychologist at Ascentem
Specialises in autism spectrum disorders and neurodiversity.
ascentem.com
Jenny Lewis , Strategic Psychology. Jenny is a Senior Clinical Psychologist who has been registered for approximately 20 years.
In the last 10 years, she has been working in private practice primarily undertaking psychological assessments for ASD, ADHD, cognitive/IQ, learning disorder, intellectual developmental disability. Jenny can be reached at https://strategicpsychology.com.au/. 02 62 62 6157
Leah Rackmann, Clinical Psychologist, at Feel to Heal Psychology. Neurodiversity-affirming and LGBTQIAP+ affirming psychologis.. Contact Leah at (02) 6189 4840 or visit https://feeltohealpsychology.com.au/.
Dr Victoria Carr at Phoenix Psychology
https://www.phoenixpsych.com.au/phenix-psychology-team
Feel to Heal Psychology Clinic
https://feeltohealpsychology.com.au/services/
Ms Paige Mewton at Paige Mewton Psychology
paigemewtonpsychology@gmail.com
Dr Gilbert Mak (Psychologist)
Evo Psychology
Here Psychology Canberra
Extensive resources on Autism
Interoception. Perceiving & interpreting signals from own bodies. Website
Alexithymia: Challenges with identifying and describing feelings. Website
Nociception: Autistic Experiences of Pain. Website
Hypermobility and Autism: Website
Self identifying as Autistic Website
Communication: Practical tips for fostering a meaningful approach Website
Eye Contact : Understanding Autistic Differences Website
Avoidant Restrictive Food Intake Disorder (ARFID). Website
Anorexia Vs. ARFID: Differences In Neurodivergent Eating Disorders. Website
Autistic Inertia: Stranded in the Moment. Website
Autism and Emotions: Autistic People Process Emotions Differently. Website
Situational Mutism: A Guide for Allies. Website
Hypersensitive & Hyper focused: An Autistic Experience of Sensory Anxiety. Website
Education on Autism
Autism Spectrum Disorder
AuDHD: why Autism is so difficult to diagnose in girls & women with ADHD
Divergent Voices YouTube Channel video
Autism & Eating Disorder Challenges video by Divergent Voices
Autism & ADHD video by Divergent Voices
Could I be on the Autism Spectrum ? video
Overlook traits of Autism in Women video
Late Autism Diagnosis in Women video by Divergent Voices
