ADHD and autism
DESCRIPTION:
New research shows that autistic symptoms determine common brain patterns in ADHD and autism – regardless of diagnosis. What does this mean for you as an adult? Understanding the diagnosis of AUDHS, autism, ADHD and neurodiversity. Psychology vs. ICD-10.
ADHD and autism in adults: Why both share the same brain signature
Have you been diagnosed with ADHD, but also recognise yourself in descriptions of autism? Or have you been diagnosed with autism, but struggle with attention problems and impulsivity? For a long time, autism spectrum disorders (ASD) and attention-deficit hyperactivity disorder (ADHD) were considered clearly separate disorders. The clinical reality – especially in adulthood – is different: up to 80% of autistic people also meet ADHD criteria. A groundbreaking study by the Child Mind Institute now shows neurobiologically that it is not the diagnosis but the severity of autistic symptoms that determines common brain patterns.
This article explains
· why our traditional diagnostics are reaching their limits,
· what this means for you as an adult, and
· how you can use these findings to improve your self-understanding and therapy.
How often do ADHD and autism occur together in adults?
The co-occurrence of ADHD and autism is anything but rare – and is increasingly being recognised in adults. Studies show that around 30–80% of people with autism also meet the criteria for ADHD. Conversely, around 30% of people with ADHD exhibit pronounced autistic traits. Many adults are diagnosed late in life – sometimes in their forties or fifties – often after years of struggling with depression, burnout, or relationship problems have led them to seek professional help.
This overlap was diagnostically problematic for a long time because, until the DSM-5 in 2013, both diagnoses could not be made simultaneously – even though clinical reality clearly showed they occurred together. For adults, this often meant that they were diagnosed with ADHD in their youth, but later showed more pronounced autistic traits. Or they were dismissed as "shy" and "oversensitive" until, in adulthood, their neurological peculiarities could no longer be compensated for.
The frequency of overlap presents practical difficulties for professionals: which diagnosis is primary? Many of my patients report diagnostic odysseys with conflicting assessments. New research suggests that this uncertainty may be inherent in the condition: if both conditions share neurobiological similarities, the categorical separation inevitably becomes artificial. The neurodivergent community has long recognised this and increasingly speaks of a spectrum of neurological differences rather than rigid diagnostic categories.
What does the new study reveal about the brain in ADHD and autism?
The Child Mind Institute study examined 166 children aged 6 to 12 using resting-state fMRI, an imaging method that measures spontaneous brain activity at rest. Sixty-three children were diagnosed with autism, and 103 had a diagnosis of ADHD. Although the study examined children, the implications for adults are highly relevant: the brain patterns identified develop in childhood and persist into adulthood.
The key finding of the study was that the more pronounced the autistic symptoms, the stronger the hyperconnectivity between the frontoparietal network (executive control, working memory, planning) and the default mode network (social cognition, self-reference, rumination). These brain patterns were evident regardless of whether the children had been formally diagnosed with ADHD or ASD. For you as an adult, this means that if you have autistic traits, your brain is likely to show this specific connectivity – regardless of your diagnostic label. At the same time, the researchers did not find any particular connectivity patterns associated with ADHD symptoms.
Particularly significant: the brain patterns identified correlated with gene expression patterns that had previously been linked to both ADHD and autism spectrum disorders. This explains why many adults recognise themselves in both diagnostic descriptions: the neurobiological basis actually overlaps. Their self-perception of "I am somehow both" has a scientific basis.
Why are the boundaries of diagnosis becoming blurred?
Traditional diagnostic systems such as DSM-5 and ICD-10 work categorically: either someone meets the criteria for a disorder, or they do not. But with ADHD and ASD or ADHD, this system reaches its limits. The symptoms overlap massively: attention difficulties, impulsivity, social interaction problems, sensory hypersensitivity to stimuli and a strong need for structure and routine are found in both areas.
New research shows that the brain does not organise itself along diagnostic categories, but along functional dimensions. As an adult, you may have pronounced autistic traits (e.g. in social communication, small talk or perception of irony), but at the same time exhibit classic ADHD symptoms such as hyperactivity or inner restlessness. Many of my patients report: "I am too restless for an autistic person, too socially awkward for someone with ADHD." Rigid categories cannot adequately represent these individual profiles.
For clinical practice in adulthood, this means that the question "ASD or ADHD?" is increasingly being replaced by a more nuanced approach: "Which symptom dimensions are pronounced and how do they affect your functioning at work, in relationships and in everyday life?" This dimensional perspective corresponds to the lived experience of many neurodivergent people who have long since ceased to identify with classic diagnostic labels.
Which symptoms overlap in ADHD and autism?
The overlaps between ADHD and autism are manifold and often manifest themselves differently in adulthood than in childhood. Both groups have difficulties with attention, but for different reasons: while inattention in ADHD is usually related to distractibility and lack of drive, in autism it often results from sensory overload (e.g. in open-plan offices) or from intense focus on special interests that block out other stimuli. Clinically, I usually see patients with ADHD forgetting appointments due to impulsivity, and autistic people forgetting due to excessive focus on a current task.
Social difficulties occur frequently in both conditions, but manifest themselves differently: autistic people often have problems empathising with others, making small talk or understanding irony. They prefer clear communication, find eye contact uncomfortable and may speak monotonously. In ADHD, social problems tend to arise from impulsivity, interrupting others or difficulty perceiving social cues due to inattention. Many adults with both conditions report: "I constantly interrupt (ADHD), but then don't understand why others react irritably (autism)."
Special sensory perception characteristics also affect both groups: those affected may be sensitive to certain noises, textures or visual stimuli. The deficit here is not in perception itself, but in the processing of sensory information. These similarities explain why many people with ADHD exhibit autistic traits and vice versa – and why an official diagnosis often has to cover both areas to capture the individual challenges adequately.
What are the neurobiological similarities?
There are remarkable parallels at the neurobiological level. The current study identified a high-speed connection between neurons in the frontal-temporal region and a group of brain regions that become active when the brain is at rest, i.e. when it is not focused on external tasks but is, for example, daydreaming or thinking about oneself (hyperconnectivity between the frontoparietal network and the default mode network) as a standard feature in pronounced autistic symptoms – regardless of the formal diagnosis. These networks are crucial for executive functions, self-regulation and social cognition. In the everyday lives of adults, this means that difficulties in organising work (frontoparietal) can be linked to social withdrawal and brooding (default mode network) – neurologically, not characteristically.
Genetic studies confirm these findings: many risk genes for ADHD and autism overlap. Genes involved in neuronal growth, synaptic functions and brain development have been identified in both conditions. The new study showed that the identified connection patterns correspond to precisely these gene expression patterns – a strong indication of common neurobiological roots. For adults, this often explains a familial clustering: "My father has ADHD, my sister has autism" – genetically possibly the same variants, phenotypically expressed differently.
What does this mean in practical terms? It explains why therapeutic approaches can often be helpful for both groups. Medications such as stimulants, which are classically used for ADHD, can also be effective for autistic people with attention problems. Conversely, adults with ADHD often benefit from structure, routine, visual aids and explicit social rules – approaches typically developed for autism. Neurobiological research underpins what clinical practice has long shown: symptom-oriented treatment is more effective than diagnosis-oriented approaches.
How are autistic people diagnosed with ADHD?
Diagnosis of co-occurring autistic and ADHD symptoms is particularly complex in adulthood. Standardised instruments such as the Autism Diagnostic Observation Schedule (ADOS-2) were developed primarily for children; in adults with high compensatory abilities, they often produce false-negative results. Many autistic adults have learned to imitate eye contact, engage in small talk and mask their peculiarities – which makes diagnosis difficult.
Since the DSM-5 was published in 2013, dual diagnosis has been officially recognised, which has simplified diagnostic practice. Nevertheless, affected adults often report conflicting assessments from different specialists. One is diagnosed with "ADHD with autistic traits," another with "autism with ADHD comorbidity" – usually depending on which specialist was consulted first. To make matters worse, many psychiatrists are unfamiliar with the modern autism spectrum in adults and still look for stereotypical "Rainman" characteristics.
New research suggests that this diagnostic uncertainty may be unavoidable if we stick to categorical systems. A dimensional diagnosis would instead state: "Pronounced autistic characteristics in social communication and sensory processing (severity X), moderate attention and executive problems (severity Y), high need for routine (severity Z)." This would not only be more precise, but would also provide direct therapeutic starting points – without years of diagnostic odysseys.
What does neurodiversity mean for those affected?
The term neurodiversity, coined by the autistic community, describes neurological differences as natural variations in human brain development – not as disorders or deficits. This perspective has fundamental implications for adults: Instead of viewing ADHD and autism primarily as conditions that need to be "cured," the neurodiversity paradigm recognises them as different ways of thinking, feeling and perceiving the world. In adulthood, this perspective is often liberating – after years of thinking "I am wrong," comes the realisation: "I am wired differently."
For neurodivergent adults, this means a fundamentally different self-perception. Instead of experiencing themselves as "defective," they can understand their neurological differences as part of their identity – with specific strengths and difficulties. Autistic people often have exceptional detail perception, pattern recognition and expertise in special interests. People with ADHD usually display creativity, spontaneity and the ability to work with high concentration in crises. These skills are valuable in the workplace – if the environment is right.
New research supports this perspective: if autistic and ADHD traits lie on standard dimensions neurobiologically, it makes little sense to speak of "normal" and "disordered". Instead, it is about understanding individual profiles and creating environments in which neurodivergent people can develop their potential – without having to constantly adapt to neurotypical expectations, which often leads to burnout, exhaustion and psychological stress in adulthood. Many of my patients report that it is only the diagnosis and the concept of neurodiversity that enable true self-acceptance.
What are the practical consequences of dimensional diagnostics?
The dimensional perspective fundamentally changes therapeutic practice with adults. Instead of asking, "Does this person have autism or ADHD?", I increasingly ask, "What specific difficulties arise in everyday life, in relationships, at work – and which evidence-based interventions address these most effectively?" An adult with pronounced impulsivity may benefit from stimulants – regardless of whether the primary diagnosis is ADHD or autism. Someone with sensory overload in the workplace needs sensory strategies – irrespective of the label.
For workplace design, this means that instead of standardised "autism accommodations" or "ADHD adjustments," individualised solutions are needed. An autistic person with attention problems may need low-stimulus rooms, structured work breaks and flexible deadlines. A person with ADHD and social difficulties benefits from opportunities for movement, explicit communication rules within the team, and home-office options to reduce stimuli.
Research into neurobiological similarities is also opening new therapeutic avenues: once common brain patterns have been identified, biological markers could be developed to predict therapeutic response – regardless of diagnostic labels. This would be true personalised medicine in the field of neurodiversity: treatment based on individual brain symptom profiles rather than administrative diagnostic codes. For my adult patients, this already means that we focus on their actual difficulties, not on textbook definitions.
What should professionals consider when making a diagnosis?
Professionals face the challenge of applying current diagnostic systems (DSM-5, ICD-10) on the one hand, while taking into account the growing evidence for dimensional models on the other. Clinically, this means that, in adults, careful recording of all symptom dimensions is more important than selecting a primary diagnosis. Autism-specific instruments such as ADOS-2 were developed for children and often only capture the tip of the iceberg in highly compensating adults. Supplementary self-reports, third-party anamnesis and the exploration of compensation strategies are essential.
Critical in adulthood: consideration of context and life history. Autistic symptoms can be masked by years of adaptation – social withdrawal only manifests itself when the individual is overwhelmed. ADHD symptoms may only appear in specific work contexts. A differentiated diagnosis captures these situational variations and the costs of compensation: how much energy does it take to appear "normal"? Where do the strategies break down?
New research also suggests that the severity of autistic symptoms is a better predictor of neurobiological patterns than diagnostic labels. Professionals should therefore not only document "Autism: yes/no" but also quantify "Social communication difficulties: pronounced; sensory sensitivity: moderate; repetitive behaviours: low; executive dysfunction: high." This dimensional information is therapeutically much more relevant than a categorical diagnosis and prevents the common problem of "you have autism, but not classic autism."
How will diagnostics change in the future?
Psychiatry and psychology are gradually moving from categorical to dimensional models. The Research Domain Criteria (RDoC) Framework of the US National Institute of Mental Health already organises psychiatric phenomena along dimensional constructs and biological levels – from genes to brain circuits to behaviour. The current study provides precisely the kind of evidence that this framework calls for. For adults, this could mean a consistent, biologically informed profile instead of frustrating changes in diagnosis ("First depression, then ADHD, now maybe autism?").
In the long term, imaging techniques and genetic markers could become part of routine diagnostics – not to confirm categories, but to create individual neurobiological profiles. In the future, an adult could receive a "brain symptom profile" that precisely describes which networks communicate with one another and which therapeutic approaches, based on similar profiles, have been most successful. This would be particularly helpful for those diagnosed late in life, who have often been confronted with incorrect diagnoses and ineffective treatments for years.
This development is not only scientific but also political: it supports the neurodivergent community's demands for individualised support rather than standardised "treatments". At the same time, it poses challenges for insurance systems based on clear diagnostic codes. The transition will be gradual – but the direction is clear: away from rigid categories and towards differentiated, biologically informed dimensions that do justice to the complexity of human neurodivergence. For you as an adult, this means validation of your experience of "not quite fitting into a box."
The most important points at a glance
Key findings on ADHD and autism in adults:
• High overlap even in adulthood: 30–80% of autistic people also meet ADHD criteria; 30% of people with ADHD show autistic traits – many receive both diagnoses late in life.
• Neurobiological commonality: Autistic symptoms (not diagnostic labels) correlate with specific brain patterns – hyperconnectivity between the frontoparietal network (working memory, planning) and the default mode network (rumination, social cognition)
• No ADHD-specific signature in this study: The identified common brain patterns correlated with autistic traits, not with ADHD symptoms – explaining why many people recognise themselves as "somehow in both".
• Gene expression overlap: Identified brain patterns correlate with genes for neural growth that are implicated in both conditions – explaining familial clusters of different diagnoses.
• Dimensional rather than categorical diagnosis: Symptom severity and individual profiles are more clinically relevant than diagnostic labels; the question "ASD or ADHD?" is increasingly being replaced by differentiated symptom dimensions.
• Therapeutic implications: Treatment should be based on specific difficulties – a person with ADHD may benefit from "autism interventions" and vice versa; medication and therapy are based on symptom clusters, not labels.
• Late diagnosis common: Many adults only receive an appropriate diagnosis after decades of difficulties; masking and compensation make detection in adulthood more difficult.
• Neurodiversity perspective: Research supports the view that neurological differences are variations, not deficits – important for self-acceptance after years of feeling "wrong."
• Workplace accommodations: Individualised solutions based on specific difficulties are more effective than standardised, diagnosis-centred disability accommodations.
• Future of diagnostics: The move towards biologically informed, dimensional profiles that capture individual brain-symptom patterns validates the experience of being "between categories."
For adults, this means that the feeling of "not really fitting into a diagnosis" has a neurobiological basis. Their individual difficulties are more important than the diagnostic label – and therapy should be based on this, not on textbook definitions.