What is AuDHD
- ADHD and Autism are both neurodevelopmental conditions involving distributed brain networks.
- 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
- There is a strong link between autism & ADHD, with both having high heritability & genetic overlap.
AuDHD is a community term for people who are both Autistic and ADHD.
AuDHD website by Dr Anna Neff
- 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.
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 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
Sensory Overstimulation
1. Reduced sensory filtering
Main brain areas involved:
- Thalamus — acts as the brain’s sensory “filter” or relay station.
- Thalamocortical pathways — connections between the thalamus and the cortex that regulate how much sensory information reaches awareness.
When this system is less efficient, more background sensory information reaches conscious processing instead of being automatically filtered out.
2. Sensory amplification (“everything feels louder or stronger”)
Main brain areas involved:
- Primary sensory cortices
- Auditory cortex → sound
- Visual cortex → light and visual information
- Somatosensory cortex → touch and body sensations
- Association cortices (especially parietal and temporal regions) — combine and interpret sensory information.
- GABA/glutamate regulatory systems across cortical networks.
These systems influence how strongly sensory information is experienced and how effectively the brain “turns down” unnecessary input.
3. Stronger threat or stress responses to sensory input
Main brain areas involved:
- Amygdala — detects emotional significance and threat.
- Salience network
- Anterior insula
- Anterior cingulate cortex (ACC)
These systems help the brain decide what feels important, urgent, or potentially unsafe. When highly activated, sensory input may feel emotionally overwhelming or threatening.
4. Cognitive overload and shutdown
Main brain areas involved:
- Prefrontal cortex (PFC) — especially the:
- Dorsolateral prefrontal cortex (DLPFC) → planning, working memory, organisation
- Ventromedial/orbitofrontal regions → emotional regulation and impulse control
- Anterior cingulate cortex (ACC) — attention control and effort regulation.
When overloaded, these systems struggle to maintain executive functioning, emotional regulation, speech organisation, and social processing.
5. Slower recovery after overload
Main brain areas involved:
- Large-scale brain connectivity networks involving:
- Prefrontal cortex
- Parietal cortex
- Temporal cortex
- Limbic system
- Default Mode Network (DMN)
- Salience Network
- Executive Control Network
These systems coordinate attention, emotional regulation, recovery, and energy use across the brain. Differences in network efficiency may increase mental fatigue and prolong recovery after overstimulation.
6. The impact of masking
Main brain areas involved:
- Prefrontal cortex (PFC) — sustained conscious self-monitoring and behavioural control.
- Social cognition networks, including:
- Medial prefrontal cortex
- Temporoparietal junction (TPJ)
- Superior temporal sulcus (STS)
Masking relies heavily on conscious monitoring, social analysis, behavioural inhibition, and ongoing self-regulation, which increases cognitive load and mental exhaustion over time.
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 may 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
- increased risk of sensory overstimulation due to amplification of underlying hypersensitivity.
RMC 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
- 25 questions
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. 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.
- 50 questions
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
RMC does screen for Autism traits, however we do not offer full diagnostic Autism Spectrum Disorder assessments at our clinic, we highly recommend the following professionals known for their expertise and compassionate approach in this area:
Dr Victoria Carr at Phoenix Psychology
https://www.phoenixpsych.com.au/phenix-psychology-team
Tabitha Frew, Clinical Psychologist at Ascentem
Specialises in autism spectrum disorders and neurodiversity.
Jenny Lewis at Strategic Psychology.
Feel to Heal Psychology.
Neurodiversity-affirming and LGBTQIAP+ affirming practice
https://feeltohealpsychology.com.au/.
Ms Paige Mewton at Paige Mewton Psychology
paigemewtonpsychology@gmail.com
Dr Gilbert Mak (Psychologist)
Evo Psychology
Here Psychology Canberra
Resources on Autism
Why Autism is so difficult to diagnose in girls & women with ADHD Video
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
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
Neurodivergent Compassion Activities & Self-Care
This data forms part of the research Phil undertook as part of his dissertation on his Masters Degree.
Researched & written by our Clinical Director Phil
AuDHD
Embrace Autism website has articles on ADHD & Autism
Neurodivergent Insights multiple articles & guides on ADHD & Autism
- AuDHD: why Autism is so difficult to diagnose in girls & women with ADHD Video
- 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
