Autism vs ADHD: How to Tell the Difference and Why Diagnosis Matters

The discussion around autism and ADHD has been taking social media by storm lately, with more and more people sharing their own diagnoses and finding communities where they can relate. As a psychologist, I welcome these conversations and encourage my clients to explore their symptoms and discuss their experiences with me so that we can collaborate on the best approaches for them.

Whether someone seeks an assessment due to a referral from a doctor, teacher, or community leader, or simply because they came across information online, a diagnosis can be a valuable tool in developing an effective treatment plan.

When I go to my doctor, I explain my symptoms, they run some tests, and give me a diagnosis for the purpose of giving me the right solutions to my problem. A doctor does not prescribe the same treatment to everyone – the treatment depends on what is bothering me. Note, however, that two people can go into a doctor’s office with a cough and they might get very different treatments if the diagnosis is different or there are other contributing medical factors that make one preferred treatment not ideal for one of the individuals.

 Just as a medical doctor would tailor treatment based on a patient’s specific diagnosis and symptoms, a psychologist will differentiate between symptoms of ADHD and autism spectrum disorder (ASD) to create a personalized treatment plan.

It’s important to note that the debate around diagnosing these conditions is ongoing, but a diagnosis can provide valuable insights and help individuals better understand their experiences. So if you’re wondering whether you or someone you know may have ADHD or autism, don’t hesitate to seek an assessment and discuss your options with a trusted healthcare professional.

What does ADHD have in common with autism?

Both ADHD and autism are neurodevelopmental disorders which means both of them are brain-based differences in brain development. The way the brain develops for each is unique but studies involving MRIs (brain scans) suggest that both have decreased connectivity to the prefrontal cortex, the foremost part of the brain responsible for executive functioning. (For a brief overview of executive functioning, read Introduction to Executive Functioning for Parents).

Weaknesses in executive functioning for both autism and ADHD explain the common symptoms that disrupt everyday functioning for these individuals:

  • Emotion regulation – having more frequent and/or bigger emotional reactions than others
  • Perseveration – getting stuck on the same idea or topic, repeating something over and over again
  • Rigid thinking – seeing things as “black or white”, “all or nothing”, and having little tolerance of things in between; lower tolerance for change
  • Social – friendships marked by more instability and fewer friends, overall
  • School/work performance – conflicts with peers/teachers
  • Attention – variable attention; hyperfocus for areas of interest and decreased focus when less interested; can be quick to change the topic

Outside of the frontal lobe, some other brain areas contribute to potential sensory differences in each (e.g., increased or decreased need for sensory input in one or more areas – sight, sound, touch, taste, hearing, and body movement).

How can you tell the difference between autism and ADHD?

With so many symptoms in common, it can be difficult to tell the difference. Here are some primary differences between the two. On a basic level, ADHD’s characteristic symptoms are inattention, hyperactivity, and/or impulsivity. Note that a child does not have to have high amounts of energy to have ADHD. What was previously called ADD, is now diagnosed as ADHD, inattentive type (to learn more about the types of ADHD, see my previous post here). With autism, the hallmark symptoms are difficulty with social communication and interaction (verbal and nonverbal communication) and having a few interests or behaviors (e.g., motor movements) that are very repetitive.

High enjoyment of novelty and new experiences – resists schedulesLoves routine and predictability – resists change
Impulsivity and inattention are the drivers of social disruptionProblems interpreting social cues are the drivers of social disruption
Hyperfocuses on an activity or hobby for a short period of time and then enthusiastically moves on to something newSpecial interests stay relatively constant over many years

Is it possible to have both?

The answer is yes! Interestingly, before 2013 when psychologists were using a previous diagnostic ruleset, they were not allowed to diagnose ADHD and autism. However, since the Diagnostic Statistical Manual Fifth Edition (DSM-5) was released, psychologists can properly now diagnose both. As a neuropsychologist, the ability to diagnose both makes a lot of sense because they are unique brain development differences. However, it is crucial that a person truly meet criteria for both conditions and that symptoms of one are not the sole driver behind the other.

Is an assessment actually useful?

Having a diagnosis of ADHD or autism also increases a person’s likelihood of having another diagnosis. Learning disabilities, oppositionality, anxiety, depression, and PTSD/trauma are just a few that cooccur with these diagnoses. An experienced psychologist should also be screening for these and others during your initial intake so that they can test for them.

Failure to screen for cooccurring diagnoses could result in misdiagnosis. For example, a student is referred for ADHD, but their attention problems are actually explained by a learning disability. Without proper testing, they may be diagnosed with something they do not have and receive treatment (e.g., ADHD medication) that will not treat their symptoms.

On the other side, sometimes an individual only receives one diagnosis and another equally disruptive diagnosis is overlooked. When a diagnosis is overlooked, the symptoms often persist which can be confusing, frustrating, or discouraging.

As you can see, accurate diagnosis of each is important to creating a treatment plan that will yield the best results. Not all psychologists are knowledgeable about the differences and similarities, so make sure to see a psychologist who is knowledgeable about both when seeking out an assessment.