ADHD and Autism: Understanding the Overlap

If you have one diagnosis and keep recognising yourself in descriptions of the other, you are not imagining it. ADHD and autism overlap significantly — in genetics, in brain circuitry, and in the daily experience of people living with them. Research suggests that 50–70% of autistic people also meet criteria for ADHD, and somewhere between 20% and 50% of those with ADHD show meaningful autistic traits. These are not rare edge cases. The overlap is the norm.

For a long time, the diagnostic systems made co-diagnosis impossible. Until 2013, the DSM-IV explicitly excluded an autism diagnosis if ADHD was already present. That prohibition has now gone. The DSM-5 allows dual diagnosis, and clinicians are increasingly trained to assess for both. But the mental health system moves slowly, and many adults who were diagnosed with one condition in childhood — or only recently as adults — are now asking: could I have both?

This article is for those people. It explains what the two conditions share, where they genuinely differ, what AuDHD (the informal shorthand for being autistic and having ADHD) looks like in daily life, and what to do if you want to pursue assessment in the UK.

What ADHD and Autism Actually Share (and Why They Get Confused)

The confusion between ADHD and autism is not a clinical error. It reflects genuine biological overlap.

A landmark 2014 review by Yael Leitner, published in Frontiers in Human Neuroscience, confirmed shared genetic architecture between the two conditions, with multiple candidate genes implicated in both. Studies using twin methodology have estimated genetic correlation between ADHD and autism at around 0.5, meaning roughly half the genetic liability for one condition is also associated with the other. This is a substantial shared foundation.

At the neurological level, both conditions involve atypical functioning in areas governing executive function: the ability to plan, prioritise, shift attention, regulate emotion, and manage working memory. Both also involve differences in the default mode network — the brain's resting state circuitry, which is active during self-reflection, mind-wandering, and social processing. In neurotypical brains, the default mode network suppresses when task-focused attention is required. In both ADHD and autism, this suppression is often incomplete, which contributes to difficulties with sustained focus, intrusive thoughts, and social reading.

Sensory processing differences appear in both. Hypersensitivity to sound, light, or texture; hyposensitivity that leads to sensory-seeking behaviour; difficulty filtering background noise — these are commonly reported across both diagnoses, though they are more reliably present in autism.

Social difficulties are also shared, though for different reasons. Both groups can struggle to pick up on unspoken social rules, read tone of voice, or feel comfortable in group settings. The result can look identical from the outside.

Executive dysfunction is perhaps the clearest shared trait. Both ADHD and autistic individuals often report difficulty with planning, time-blindness, task initiation, and emotional regulation — particularly rejection sensitivity, which is formally termed rejection-sensitive dysphoria in the ADHD literature but is widely reported by autistic adults as well.

The Key Differences: Executive Function, Masking, and Social Patterns

Shared traits do not mean identical conditions. ADHD and autism are distinct in their core mechanisms, and getting this right matters for treatment.

The stability question

Autistic traits tend to be stable across contexts, though they may be expressed differently depending on environment. The autistic brain is often characterised by strong pattern detection, a tendency toward routines and sameness, deep focus on specific subjects (sometimes called monotropism — the channelling of attention into one topic at high intensity), and a relatively consistent preference architecture. Change is frequently experienced as aversive.

ADHD symptoms, by contrast, are famously context-dependent. The hallmark is not an inability to focus, but an inability to regulate focus on demand. Interest-based dopamine dysregulation — a phrase associated with the work of psychiatrist William Dodson and researcher Ari Tuckman — means that ADHD brains are activated by novelty, urgency, challenge, or passion, and can struggle profoundly with tasks that are dull, repetitive, or externally imposed. This variability is less typical in autism.

Masking and its different roots

Both conditions involve masking — the effortful suppression of natural responses in order to appear neurotypical. But the mechanisms differ.

In autism, masking often involves consciously suppressing stimming (self-regulatory movements or sounds), scripting social interactions in advance, mirroring others' behaviour, and suppressing sensory responses. Research by Dr Sarah Cassidy and colleagues at the University of Nottingham has found that autistic people who mask heavily show significantly higher rates of anxiety, depression, and suicidal ideation than those who mask less.

In ADHD, masking tends to look different: presenting as calm and attentive while internally dysregulated, managing to hold it together in structured environments and collapsing at home, or spending enormous cognitive energy on appearing organised while inwardly overwhelmed.

Social patterns

In autism, social difficulties often trace to differences in social motivation, differences in social comprehension (difficulty reading implicit cues, non-literal language, social hierarchy), and sensory overwhelm in social environments.

In ADHD, social difficulties more commonly arise from impulsivity (interrupting, speaking before thinking), inattention (missing what someone said), emotional dysregulation, and poor working memory. ADHD social difficulties are less consistently present and more tied to executive function than to social comprehension.

When both are present, these patterns can compound.

What AuDHD Looks Like in Practice

AuDHD — the informal shorthand widely adopted in the autistic and ADHD communities — is not a formal clinical term, but the experience it describes is real.

People who are both autistic and have ADHD often report that the two conditions create apparent contradictions. They may be deeply routine-dependent (a common autistic trait) but also easily bored and craving novelty (a common ADHD trait). They may have intense, persistent special interests (monotropism) that are also subject to ADHD hyperfocus — meaning they can disappear into a topic for days, but the specific topic shifts over time.

Sensory overload and executive dysfunction can interact: a sensory environment that is distressing can consume the executive resources needed for focus, planning, and self-regulation, leaving very little left for anything else.

Clinicians writing on co-occurring conditions — including Antshel et al. in a 2011 paper published in the Journal of Child Psychology and Psychiatry — note that children with both conditions showed more severe impairment than those with either alone across multiple domains, including academic functioning, social competence, and behavioural regulation. This is not a reason for alarm; it is a reason to ensure that assessment is thorough and that support addresses both conditions.

Why Getting Both Diagnoses Matters

The clinical community has largely moved on from treating ADHD and autism as mutually exclusive. But the legacy of the old exclusion still surfaces in clinical practice. Some practitioners, particularly those trained before 2013, will still assess for one condition and stop if they find it.

This matters practically because the two conditions have different treatment pathways. ADHD responds to stimulant medication (methylphenidate, lisdexamfetamine) in a way that autism does not. Stimulant medication improves the dopamine regulation underlying ADHD inattention, impulsivity, and emotional dysregulation. It does not address autistic traits — social processing differences, sensory sensitivities, preference for routines.

A dual diagnosis also opens different support pathways: ADHD coaching, which focuses on external structure and accountability; autism-specific support such as occupational therapy for sensory regulation; and the legal protections that come with each recognised disability under the Equality Act 2010.

In the UK, there is also growing recognition of the late-diagnosis experience for both conditions. A 2022 NHS England report on neurodevelopmental pathways acknowledged significant diagnostic delays, with autistic women in particular diagnosed on average several years later than autistic men. Many adults now seeking assessment were raised at a time when autism was understood primarily as a condition affecting non-verbal children, and ADHD was associated mainly with disruptive behaviour in boys.

How to Pursue Assessment in the UK

The starting point in most cases is a GP referral. You can ask your GP to refer you for autism assessment and ADHD assessment separately or together. Wait times on the NHS vary significantly by region and can be substantial.

Right to Choose is a provision under NHS rules that allows patients in England to choose a provider for certain services, including in some areas neurodevelopmental assessment. Providers such as Psychiatry UK and ADHD 360 operate under Right to Choose contracts with some NHS commissioners, allowing patients to be seen more quickly by an independent provider at NHS cost.

For autism specifically, the National Autistic Society (NAS) provides clear guidance on the assessment process, what to expect, and how to raise concerns if you feel your presentation has been dismissed.

Private assessment is available from specialist psychiatrists and psychologists. If you go this route, ensure any professional you see is appropriately accredited — for autism, look for assessors trained in tools such as the ADOS-2 (Autism Diagnostic Observation Schedule).

When seeking assessment, it helps to document your history before appointments: specific examples of where you struggle, how long these difficulties have been present, and what strategies you have used to cope. Bringing someone who knows you well to provide collateral information can also strengthen the picture for clinicians.

What Helps When You Have Both

Structure Without Rigidity

Both ADHD and autism benefit from predictable structure. For autistic individuals, routines reduce the cognitive load of decision-making. For people with ADHD, external structure substitutes for internal self-regulation that is genuinely harder to sustain.

What tends to work is structure with built-in flexibility: consistent frameworks that allow variation within them. The Priority Pad works well for this purpose: it provides a consistent daily structure while the daily page means you are never trying to match today to yesterday.

Sensory-Aware Environments

Executive function is not separate from the sensory environment. When the environment is aversive — too loud, too bright, too unpredictable — executive resources are consumed managing distress, leaving less available for everything else. Noise-cancelling headphones, natural light rather than fluorescent, clear desk surfaces — these are adaptations that free up cognitive capacity for the work that matters.

Planning Tools for AuDHD Brains

Planning is harder when you have both ADHD time-blindness and autistic all-or-nothing thinking. Breaking tasks into concrete, very small steps addresses both: each step is achievable now, and the sequence provides structure.

The Could Do Pad is useful here: its explicit separation of priority from could-do reflects the AuDHD reality that not everything on the list is possible today, and naming that is not failure.

For reflection and tracking patterns — which conditions are worse on which days, what environments help, what tasks consistently stall — a journal builds self-knowledge that no clinician session can match. The Morning Mindset Journal uses a consistent daily format that suits the autistic preference for routine while being brief enough to sustain with ADHD attention: a 15-minute session in the morning creates the day's frame rather than taking the day over.

Related Reading

• ADHD Masking: What It Is and the Cost of Keeping It Up
• ADHD Burnout: What It Is and How to Recover
• ADHD in Women: Why It Looks Nothing Like You'd Expect

When to Take It More Seriously

If you are struggling significantly — with work, relationships, mental health, or daily functioning — and have not been assessed, it is worth pursuing that assessment. The NHS, the National Autistic Society (nas.org.uk), ADHD UK (adhduk.co.uk), and Neurodiversity in Business all provide guidance on next steps in the UK.

Frequently Asked Questions

Can you have both ADHD and autism?

Yes. The DSM-5, published in 2013, removed the previous exclusion that prevented dual diagnosis. Research now shows that 50–70% of autistic people also meet criteria for ADHD, and around 20–50% of people with ADHD show meaningful autistic traits. Dual diagnosis is common and increasingly well recognised in clinical practice.

How is AuDHD different from having just ADHD or just autism?

People with both conditions often experience the traits of each in ways that interact with and compound each other. The routine-preference of autism can sit alongside the novelty-seeking of ADHD. The social difficulties of autism can be added to by the impulsivity and inattention of ADHD. Sensory overload can reduce the executive capacity that ADHD already challenges.

Why was I told I couldn't be diagnosed with both?

This was the clinical rule under DSM-IV (in use before 2013), which explicitly excluded autism if ADHD was already diagnosed, and vice versa. This rule has been removed in DSM-5. If you were assessed before 2013, or by a clinician who trained primarily on DSM-IV criteria, your assessment may not have considered both conditions.

How long does it take to get assessed for both in the UK?

NHS wait times vary significantly by region. Currently, some areas have waits of two years or more for autism assessment; ADHD waits are similarly variable. The Right to Choose provision can provide access to providers such as Psychiatry UK or ADHD 360 on an NHS-funded basis with shorter waits. Private assessment is available more quickly but involves significant cost.