Until recently, autism and ADHD were thought to be mutually exclusive. However, recent research shows that these neurotypes very often coexist. This increases diagnostic and therapeutic challenges, but also leads to a better understanding of how individuals function.

The comorbidity of autism and ADHD remains poorly understood and under-researched. Until 2013, these diagnoses were considered mutually exclusive. However, current research suggests that autism (ASD) and ADHD share many genetic and neurobiological characteristics, which may explain why they often co-occur in families and even in individuals. This shift has led to an increase in the number of co-occurring diagnoses (so-called AuDHD).

"Research shows that 40-70% of autistic people also have ADHD. My clinical experience suggests it's around 60%. In other words, most autistic people also have some ADHD characteristics, sufficient to warrant a dual diagnosis," said Prof. Tony Attwood from Griffith University in Australia during the Neuroshow conference, which took place on October 10–11 in Warsaw.

The situation isn't the same the other way around: most people with ADHD don't have autism. However, the numbers are still impressive. A 2020 study estimates that 1 in 8 people diagnosed with ADHD also have ASD.

In some cases, a person may not meet all the diagnostic criteria for both ADHD and autism. For example, a person with ADHD may have more autistic traits than the general population, but not enough to make a clinical diagnosis—and vice versa.

Both neurotypes are characterized by deficits in executive function, social function, and emotional intelligence, with the co-occurrence of ADHD and ASD often leading to impaired executive function. Social dysfunction and difficulties with emotion regulation are also common and are exacerbated when both conditions co-occur. This diagnosis leads to a lower quality of life than ADHD and ASD alone.

ADHD and Autism Comorbidity Is a Challenging Diagnosis

Autism and ADHD, when diagnosed individually, can significantly impact daily life. However, when diagnosed together, they can exacerbate each other's symptoms, creating even more barriers and challenges than a single diagnosis.

There are several hypotheses regarding the causes of the frequent comorbidity of ADHD and autism. One leading theory is a shared genetic etiology. Twin studies show significant genetic overlap (approximately 50–72%) between these two neurotypes, suggesting that genetics may play a role in their frequent comorbidity in individuals and families.

Another theory suggests that comorbidity may result from shared neurobiological mechanisms, particularly those involving executive function, attention, and the reward system.

However, further research is needed to fully understand the complex causes of the overlap between ADHD and autism.

"Patients with ADHD most often complain not so much of a deficit in attention, but of paying attention to everything and feeling overwhelmed." They are unable to identify what is important and manage it. The part of the brain responsible for prioritizing, integrating, and sorting information is underperforming. Their brains function like a Ferrari with bicycle brakes. They lack a cataloging system, or—as doctors call it—executive function. Therefore, they lack the ability to pay attention, explains the specialist's explanation of the difficulties faced by people with ADHD.

People with ADHD don't devote time to things that don't interest them. However, if they are motivated and interested, they can focus intensely.

An autistic person perceives the world differently due to their different sensory processing, which can lead to hypersensitivity or hyposensitivity to sounds, light, touch, smells, and tastes. They don't like to cuddle, eat certain foods, or look people in the eye.

Maintaining relationships with peers in both cases requires enormous effort, often accompanied by a fear of failure. Hence, among people with autism and ADHD, we have fewer friendships, and those that do exist tend to be fluid due to emotional impulses, hyperreactivity, and frequent conflicts.

"Adolescence makes people with ADHD feel increasingly lonely and can expose themselves to even greater risks than their peers—for example, experimenting with early sexual intercourse or substance abuse. 

When they are unable to maintain attention, they experience emptiness and anxiety, because when nothing happens, they perceive it as a very unpleasant experience. So they seek new experiences because they need a strong impulse, a drive," explains Professor Tony Attwood.

People with autism can hide and mask, but this is extremely exhausting. Some say they don't accept that they have to create unreal perceptions to meet others' expectations, thus losing themselves. They become chameleons, and if they fail to meet these expectations, they struggle with feelings of rejection.

The main problem in ADHD and autism is executive function, which is crucial for planning, organization, concentration, and flexible thinking. With ADHD, we often talk about procrastination, or putting off tasks until later. How can one plan to start a specific activity when time awareness fails? Therefore, such individuals often have numerous projects underway and operate in a chaotic environment. Loved ones observe that initial enthusiasm quickly fades, leaving behind a multitude of unresolved issues that generate problems.

Cognitive flexibility, the ability to change one's way of thinking, adapt to new situations, and respond to unexpected events, is also impaired in autism spectrum disorder. This is crucial not only for our well-being but also for effective action in everyday matters, as it allows us to avoid rigid thinking and respond more openly to challenges.

Auditory processing and memory—used when conveying verbal instructions—also often fail, leading to them being forgotten.

ADHD and ASD: Much in Common, Many Differences

Besides many common features, ADHD and autism spectrum disorders also share many differences. For example, people with ADHD have difficulty inhibiting their reactions and impulsivity. In autism, the situation is the opposite: the time to process information and react is prolonged.

People on the spectrum often say, "I don't know if I can handle this, if I can do this, I need to think about it." Those with ADHD undertake things with enthusiasm but overestimate their abilities or don't complete tasks because they have difficulty planning.

People with ADHD can be impulsive and sociable, while those with ASD have difficulty picking up on signals and connecting with others. Due to hyperactivity, ASD often dominate social interactions, while ASD can be withdrawn and may have difficulty expressing their feelings.

Perception of People with Autism and ADHD

Very often, in childhood, the behavior of people with ADHD is misinterpreted by parents or teachers, often hearing: "You're lazy, rude, or mean."

Peers also misinterpret the behavior of these individuals – they perceive them as rude and aggressive, often saying: "I don't want to play with you because you break toys or get into trouble, I'd rather avoid contact and play with you."

In contrast, people with ASD may have difficulty establishing relationships, experience a dislike for social gatherings or group work; are reluctant to express their feelings; and dislike discussing emotions. They tend to take everything very literally, avoiding eye contact during conversations; This can lead to them being perceived as "loners," "people-averse," "weird," or "different."

"Now imagine a person who has characteristics of both ADHD and autism spectrum disorder (AuDHD). This creates confusion," says Professor Attwood.

A person with ADHD enjoys spontaneity and loves trying new foods, while people on the spectrum will be very picky about the taste and texture of food, so such a person will be careful about what's on their menu. People with ADHD love new experiences, but autistic people need predictability and consistency.

"Being a person with AuDHD sometimes makes me feel like a walking contradiction. I can become absorbed in an activity, only to lose interest after a few days, or forget to meet my basic needs when the hyperfixation becomes overwhelming. However, this isn't entirely negative—for me, AuDHD also means excelling in areas of interest and being incredibly empathetic," says George, an adult with AuDHD. There's no cure for ADHD or autism, as they aren't diseases. These diagnoses simply mean that the brain works differently and in a certain way. So when doctors talk about ADHD and ASD treatments, their goal isn't (or shouldn't be) to "fix" the person, but to lessen the impact of developmental differences on their ability to live the life they desire.Monika Grzegorowska/2025