Autism vs ADHD: What Are the Differences?

Autism and attention deficit hyperactivity disorder (ADHD) are both listed in the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, Text Revision, as neurodevelopmental disorders, meaning that they emerge in childhood. Autism and ADHD have similarities that can be challenging to distinguish. They can also co-occur.

Current research estimates that 50% to 70% of autistic people also have ADHD. In this article, you'll learn more about the differences between autism and ADHD and how they are distinguished.

Characteristics

There are many similarities between autism and ADHD. Both autistic people and those with ADHD can experience impulsivity, hyperactivity, and difficulty with focus and attention.

Although both autistic people and those with ADHD can struggle with inattention, while people with ADHD struggle with inattention in all aspects, autistic people can focus when they find a task that interests them. In fact, in some scenarios, they might even become hyper-fixated. 

Diagnostic Criteria for Autism 

Autism is typically marked by social communication style and behaviors that are not consistent with neurotypical norms. Common examples of these symptoms can include:

• Discomfort with direct or sustained eye contact
• Not responding verbally when called
• Difficulty accurately interpreting people's emotional cues 
• Using atypical tone, rhythm, or volume of voice
• Repeating certain words or phrases
• Having a specific routine and struggling to function if it's disrupted 

Traits of ADHD 

On the other hand, ADHD manifests as inattention, hyperactivity, and impulsivity. Some people with ADHD primarily experience inattentive symptoms, some experience predominantly hyperactive-impulsive presentation, and some experience a combination of both symptom sets. Inattention symptoms make it difficult for people with the condition to be focused or organized. Those who experience hyperactivity may experience restlessness and fidgeting. Impulsivity makes it difficult for a person with this condition to exhibit self-control.

Common ways in which ADHD can manifest include: 

• Being easily distracted 
• Difficulty carrying out organized tasks and activities 
• Being forgetful even with daily activities 
• Speaking excessively 
• Often interrupting others when they are speaking 
• Having difficulty waiting their turn 
• Being constantly "on the go"

Causes 

We do not fully understand how autism or ADHD develop. What is clear is that a combination of genetic and environmental factors come into play with their development. Both also affect the brain, albeit in different ways. 

Causes of Autism 

There is no single cause of autism. Some research shows that autistic people are more likely to have some chromosomal disorders, such as Fragile X Syndrome, compared to non-autistic people. Other risk factors that increase the likelihood of autism developing include: 

• Having an autistic sibling
• Pregnancy complications 
• Being born to older parents 

Causes of ADHD 

Although it's unclear what causes ADHD, certain things make people more likely to have ADHD. It is not definitively known if these factors cause ADHD or if people who develop ADHD are also more likely to experience these factors. Some of these risk factors include: 

• Being born prematurely 
• Early exposure to environmental toxins 
• Substance use during pregnancy 
• Low birth weight 
• Brain injury 

Diagnosis 

A person can be diagnosed with both autism and ADHD (sometimes referred to as AuDHD, though this is not a clinical term). However, no specific medical or blood tests can be done to diagnose either disorder, which can make diagnosing both conditions challenging. 

Diagnosis of Autism

The American Psychiatric Association's Diagnostic and Statistical Manual (DSM-5-TR) provides specific criteria for the diagnosis of autism. According to the DSM-5-TR, for a person to be diagnosed with the condition, they must exhibit deficits in the following areas social communication and interaction. 

• Persistent and unusual social interactions 
• Difficulty forming and maintaining relationships with people 
• Difficulty with non-verbal communication

They should also exhibit at least two forms of the following restricted and repetitive behaviors.

• Repetitive behaviors with movement or speech
• Having unusually fixated interests 
• Being either too sensitive or under-sensitive to sensory stimuli 
• Having inflexible routines and becoming distressed when it's disrupted 

The DSM-5 also provides that symptoms must be severe enough to disrupt daily functioning. 

While the DSM-5-TR criteria for autism use language about it being a "disorder," the autistic community has worked to change the language and understanding of an autism diagnosis and what it means to be autistic.

Diagnosis of ADHD 

The DSM-5-TR is also used to help diagnose ADHD in children and adults. The manual provides a diagnostic standard to prevent misdiagnosis of the condition and help ensure people with the condition get the treatment they need as soon as possible.

The same rule applies to symptoms of hyperactivity and impulsivity. The signs should also occur in two or more locations. For instance, at home and in school, and be severe enough to interfere with daily functioning. 

Again, the language used in the DSM emphasizes deficits while the neurodiversity-affirming movement emphasizes that ADHD, like autism, is a neurotype difference that comes with both strengths and difficulties.

Management

ADHD and autism manifest differently for each individual. Support needs and treatment will vary based on individual needs. Both autistic people and those with ADHD may benefit from cognitive-behavioral or other therapies to cope with difficulties that come from being neurodivergent in a world developed for neurotypical standards as well as any comorbid mental health issues, such as depression or anxiety.

Management for Autism 

As a neurotype, autism is not a "problem" to be "cured." However, if an autistic person experiences irritability that interferes with their quality of life, Risperdal (risperidone) and Abilify (aripiprazole) are antipsychotics that the FDA has approved to address this difficulty.

Autistic people may also benefit from antianxiety and antidepressant medication for comorbid mental health issues.

Management for ADHD 

Medication used for treating ADHD include both stimulant and non-stimulant medications. These medications help manage neurodivergence and can be administered to children as young as six.

These medications can help improve concentration, reduce impulsive behavior, and improve learning: 

• Stimulants: These are the most common type of ADHD medication. Stimulants boost activity in the brain's parts that control your behavior and attention. Adderall (amphetamine/dextroamphetamine), Ritalin/Concerta (methylphenidate), Focalin (dexmethylphenidate) and Vyvanse (lisdexamfetamine) are all commonly used.
• Non-stimulants: Only three non-stimulant medicines have been approved by the FDA for the treatment of ADHD. They are Kapvay (clonidine), Strattera (atomoxetine), and Intuniv guanfacine). In 2021 the FDA also approved Qelbree (violxazine) for treating ADHD in adults and children older than six. They generally work slower than stimulants but are an excellent alternative for people who don't cope well with the side effects of stimulants. 
  

A Word From Verywell

ADHD and autism are both neurotypes that affect the brain's development and can cause impairment. However, although the characteristics overlap, they are distinct from each other.

Both ADHD and autism have different diagnostic criteria, and people with each have unique support needs. It's also possible for both conditions to overlap. This means that some autistic people could also have ADHD.