ADHD and Autism

What is the connection between ADHD and autism?

Autistic people are more likely to also have ADHD, even though the two diagnoses are very different. What is ADHD? It's a difference that makes it harder to pay attention and concentrate. Often the person can also be impulsive and hyperactive. ADHD does not make you less intelligent.

Attention deficit disorder (ADHD) and autism are very different disorders. Yet around 30% of autistic people also have a diagnosis of ADHD. These two conditions have contradictory symptoms. In fact, being autistic and having ADHD is a bit like having two forces pulling Quel est le lien entre le TDAH et l’autisme in opposite directions: one force pulling towards order and routine, the other towards impulsivity and improvisation. For autistic people and ADHD, it can be difficult to distinguish which traits come from autism and which from ADHD.


ADHD comprises two categories of traits: inattention, hyperactivity and impulsivity. To be ADHD, you need to have 6 or more traits in at least one of these categories. Here are some of the traits that make up ADHD.


Impulsivity and hyperactivity

These traits, although specific to ADHD, can often be confused with those of autism, and vice versa. For example, impulsive behaviours such as talking a lot and cutting others off in conversation can resemble autistic traits of social communication. Autistic traits related to social communication include difficulty understanding the implicit rules of communication. This trait can make it difficult for an autistic person to understand turns of speech. A diagnosis of autism may therefore prevent them from perceiving the impulsivity behind responding too quickly or cutting others off. Also, a diagnosis of ADHD could mask the difficulties in understanding the rules of social communication associated with autism.

So it’s important to be vigilant when making a diagnosis. It’s important to be open to the fact that certain behaviors may stem from a condition other than autism.

Autism and ADHD: two opposing forces

Many autistic people attach great importance to their routine, and have a taste for uniformity. This means that autistic people usually prefer to follow an already familiar schedule and use the same objects and products over and over again (e.g., one brand of cereal). This contrasts with the impulsivity often seen with ADHD. Indeed, ADHD sufferers have great difficulty maintaining a routine.

In fact, ADHD and autism bring with them needs that can be difficult to reconcile. For example, to avoid feeling bored and losing concentration, people with ADHD feel the need to experience new sensations. They will therefore seek out a variety of experiences, whether by meeting new people, changing hobbies or never playing the same video game for more than two weeks at a time. Autistic people, on the other hand, prefer routine and uniformity. It’s a need. Uniformity and routine help avoid sensory overload and autistic meltdowns. These needs are contradictory, yet autistic and ADHD people can have them all at the same time.

Autism and ADHD: some similarities

Autism and ADHD share common characteristics. People diagnosed with both ADHD and autism have social difficulties, even if these difficulties are different (see previous example).


Autistic people, like people with ADHD, have self-regulating behaviors called stims. Stims include a wide variety of behaviors, such as sticking a weighted (heavy) doggie or listening to the same song over and over again; there’s something for everyone. Stims are thought to have different functions in autism than in ADHD.

In autism, stims can help by providing a known sensation that helps the brain to understand and manage other, unknown sensations.

Further information

In autism, stims help avoid sensory overload by providing a point of comparison for the brain, which can use a uniform sensation to better understand different sensations. For people who have ADHD, stims can stimulate a brain that would otherwise find reality too boring to pay attention to. Stims can be used for both functions in the same person.

Both autism and ADHD can cause executive dysfunction, i.e. difficulties in functioning that interfere with the completion of everyday tasks. Thus, both ADHD and autistic people may have difficulty starting or completing a new task. Autistic people may find it difficult to continue with a task, because if something unexpected happens, they can no longer coordinate their actions. For example, if the soap is not in the same place as usual in the bathroom, it can be difficult to finish a shower. Some autistic people plan each of their movements in advance; if one object is moved, all subsequent movements must be modified. This can make a task more difficult to complete.

People with ADHD may have difficulty completing a task because they no longer have the concentration needed to continue. The brain is “bored”, and no longer has enough dopamine (the motivating neurotransmitter) to continue the task properly. The person risks not completing the task or making careless mistakes. Autistic people and ADHD can also be distracted by external stimuli.

A person who has both ADHD and autism will see their autistic and inattentive traits combine, increasing these difficulties.


Sometimes, ADHD can compensate for the difficulties of autism, and vice versa. For example, the impulsivity inherent in ADHD can help a person with autism to change their routine or overcome cognitive rigidity. On the other hand, the presence of a strict routine in autism can reduce the chances of forgetting or losing objects due to inattention.

Autism can be associated with the ability to pay attention to detail. Thus, the difficulty of paying attention to detail in ADHD can be compensated for. The details that autistic people observe are different from those of allistic (non-autistic) people. ADHD sufferers can also experience periods of hyperfocus, when they become so absorbed in one subject that they forget everything else. These are moments when the concentration required to complete a task is very high. This moment of concentration, combined with attention to different details, can enable autistic people and ADHD to accomplish tasks that only they can do in this way, which can be a strength in the arts in general. And art is everywhere! Drawing, writing, graphic design, photography, sound arrangements are all around us, from the little sound that tells us our computer has just opened, to the architecture of our homes. The difference in artistic expression multiplies the possibilities.

I have two specific interests: biology and human rights. But over the course of my life, I've had dozens of hyperfixations, most of which relate to one or other of my specific interests. For example, I've had hyperfixations on fashion, sewing and the history of clothing. Each time, it has given me a more nuanced understanding of the human body and the social dynamics behind the discrepancies in respect for human rights.


Les personnes avec un diagnostic de TDAH ont souvent des hyperfixations, c’est-à-dire des sujets d’intérêt dans lesquels elles s’investissent avec passion pour une courte période allant de quelques heures à quelques semaines. Les personnes autistes ont souvent des intérêts spécifiques, c’est-à-dire des sujets d’intérêt dans lesquels elles s’investissent sur une longue période allant de quelques mois à plusieurs années, voire toute leur vie. Les personnes à la fois TDAH autistes peuvent avoir les deux types d’intérêts. Cela leur donne la possibilité de devenir expertes dans un sujet et de diversifier leur expertise grâce à l’exploration d’autres sujets variés.

Catherine Bouchard-Tremblay

Science popularizer