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ADHD Vs. Autism in Adults: What's the Difference

October 11th, 2023


Neurodevelopmental disorders are complex conditions that begin at early developmental stages. They can have very different presentations and can influence an individual's quality of life and functioning. Autism and ADHD are both under the umbrella of neurodevelopmental disorders. Autism affects about 1.5% of the worldwide population. ADHD affects about 5% of people worldwide.

Autism and ADHD are more prevalent neurodevelopmental disorders, but there can also be misconceptions about them. Each has distinct traits, as well as unique strengths and challenges. This blog post will provide an overview of autism and ADHD and discuss their symptoms, the process of diagnosis, and potential interventions. Finally, this blog post will address the similarities and differences between autism and ADHD.


Autism affects how individuals communicate, behave, and interact with others. Because it exists on a spectrum, a wide range of symptoms and behaviors can contribute to a diagnosis.

Symptoms of Autism

The symptoms of autism spectrum disorder (ASD) include:

  • Deficits in Social Interactions: Individuals with autism may struggle with, or have limited interest in, social interactions. They may have issues with nonverbal communication, such as interpreting others' body language. As a result, forming and maintaining relationships can be challenging.1,3
  • Repetitive, Restrictive Patterns of Behavior: Individuals with autism may engage in repetitive behaviors, such as motor repetitions (e.g., hand flapping, and repeating phrases).4 They may also develop fixed interests around specific topics, objects, or activities.1 Some fixed interests can be intense attachments to specific TV shows, toys, or hobbies.
  • Intellectual or Language Impairments: Some people with autism may have intellectual or language impairments that can vary in severity.1 According to recent studies, 38% of children with ASD have an intellectual disability. These individuals may struggle more with social and communication skills.5

Because autism occurs on a spectrum, specific symptoms vary from person to person. Those at lower severity levels may be independent and only need minimal support. Those with more severe issues may require more extensive, long-term assistance. This severity may vary based on context.1

Symptoms of Autism

Diagnosing Autism

The following criteria apply for an ASD diagnosis:

  • Early Onset: Symptoms must be present from a young age, often around age two or three. Some markers may even be present at younger ages. These include delays in speech and language development and other developmental milestones.6
  • Impact on Functionality: These symptoms must impact an individual's functionality in several areas of life. These domains include family, social, academic, or career.1

Professionals who specialize in ASD diagnosis can diagnose autism. These include medical professionals (pediatricians, psychiatrists, etc.) and mental health professionals (psychologists). Related professionals, such as speech-language pathologists or occupational therapists, may also diagnose autism.7,8

Several factors contribute to a diagnosis. They can include an individual's behavior, developmental history, input from close contacts, personal interviews, and diagnostic evaluations (including psychometric testing).9 Not everyone receives an autism diagnosis in childhood.

A diagnosis can help individuals understand their specific challenges and support options.

Interventions for Autism

Because each individual's experience of autism is unique, treatment will address specific needs. Goals can be to increase independence and reduce daily challenges. Some interventions include behavior therapy, speech-language therapy, occupational therapy, and physical therapy. Social skills training, individual therapy, and family therapy may also be helpful.10,11,12

The presence of other medical issues may influence treatment approaches.


Attention-Deficit/Hyperactivity Disorder (ADHD) is characterized by difficulties with attention, concentration, hyperactivity, and impulsivity. Some individuals may struggle more with attention than hyperactivity, and vice versa. Some may present with several symptoms in both areas.1

Symptoms of ADHD

Symptoms of ADHD

Symptoms associated with ADHD fall under two categories: inattention and hyperactivity-impulsivity.

Inattention symptoms include:

  • Difficulty paying attention to details or when others are talking
  • Difficulty sustaining attention for long periods
  • Difficulty following instructions and/or completing tasks
  • Struggling with organizing and/or time management
  • Avoiding tasks that require sustained effort
  • Often losing or misplacing things
  • Being easily distracted
  • Being forgetful

Hyperactivity-Impulsivity symptoms include:

  • Frequent fidgeting
  • Difficulty staying in place
  • Being or feeling restless
  • Excessive talking
  • Often talking over or interrupting others in conversations
  • Answering questions before the speaker finishes the question
  • Difficulty in waiting their turn

Not every symptom has to be present for an ADHD diagnosis. However, a certain number must be present in each category to receive the diagnosis. Criteria for diagnosing ADHD vary from child to adult.1,13

Diagnosing ADHD

For an ADHD diagnosis, the following criteria apply:

  • Early Onset: Symptoms must have been present since before age 12.
  • Duration: Symptoms must have occurred for at least six months.
  • Impact on Functionality: These symptoms must impact an individual's functionality in several areas of life. These domains include family, social, academic, or career.1 For children, functionality may be impacted at home and school. Adults may experience significant difficulties managing tasks at work or home, as well as feelings of restlessness that get in the way of other activities. Making or sustaining relationships may also be challenging.13,14

Qualified medical or mental health professionals or related specialists can diagnose ADHD. Observation, diagnostic evaluations, and interviews help these professionals arrive at an ADHD diagnosis.13,15 Not everyone receives an ADHD diagnosis in childhood.

Interventions for ADHD

Treatment options for ADHD include:

  • Behavior modification: Learning behavioral interventions can help individuals strengthen their executive functioning skills.16 They can put in place strategies to organize their environments. These skills can help them manage impulsivity and deal with daily stressors.
  • Medication management: Medication may help make ADHD symptoms more manageable for some individuals with ADHD.16 Medication may improve motivation, attention, and concentration.
  • Individual therapy: Individual therapy may help individuals strengthen emotional regulation and distress tolerance skills. It may also help them work through potential mood issues related to living with and managing ADHD.

Those with ADHD may have other mental health issues like anxiety or depression. Treating these issues may also help individuals better cope with their ADHD symptoms.

Relationship Between Autism and ADHD

Relationship Between Autism and ADHD

There can be similar behaviors and challenges between autism and ADHD. Symptoms of these disorders can present at early ages. Symptoms may contribute to issues with executive functioning, learning, or socializing. There may be emotional regulation and sensory issues and challenges with sustaining attention and task switching in both disorders. Individuals with these disorders can struggle to manage daily tasks and address life stressors.

Both ADHD and autism can co-occur with other mental health and medical issues.

Differences Between Autism and ADHD in Adults

ASD and ADHD each have specific characteristics. These distinctions account for the main differences between autism and ADHD in adults. Adults with autism may have social deficits, repetitive behaviors, and restricted interests. Adults with ADHD may experience attention, concentration, hyperactivity, and impulsivity issues. Intellectual and language development issues are not criteria for an ADHD diagnosis.

Similar symptoms, such as communication issues, differ in presentation between autism and ADHD. Adults with autism may strain to start and sustain conversations. They may have limited interest in conversing. Adults with ADHD may struggle with excessive talking or impulsivity issues in conversations. Understanding these differences can help distinguish between autism and ADHD.

Autism and ADHD present with distinct characteristics, challenges, and strengths. More knowledge about these disorders can deepen individuals' awareness of their symptoms. Understanding diagnostic criteria and potential treatment approaches can help empower individuals to seek support where needed.

Written By: Sarah Tarabey, LCPC

Clarity Clinic

At Clarity Clinic, we have highly trained staff specializing in therapy and psychiatry services. Clarity Clinic currently offers Medication Management, Therapy, and TMS Services across Illinois. To learn more about how we can support your mental health, call Clarity Clinic at (312) 815-9660 or schedule an appointment today.

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1. American Psychiatric Association. (2013). *Diagnostic and Statistical Manual of Mental Disorders* (5th ed.).

2. MDPI. (2021). Where Do Neurodevelopmental Disorders Go? Casting the Eye Away from Childhood towards Adulthood. Healthcare, 11(7), 1015.

3. Autism Speaks. (n.d.). What is autism? [Website].

4. Caldwell-Harris, C. L. (2021). An Explanation for Repetitive Motor Behaviors in Autism: Facilitating Inventions via Trial-and-Error Discovery. *Frontiers in Psychiatry, 12*, 657774.

5. Children's Hospital of Philadelphia. (n.d.). Intellectual disability and ASD. [Website].

6. Autism Speaks. (n.d.). Signs of autism. [Website].

7. Centers for Disease Control and Prevention. (n.d.). Autism screening and diagnosis. [Website].

8. Children's Hospital of Philadelphia. (n.d.). Who is able to diagnose autism spectrum disorder? [Website].

9. National Institute of Mental Health. (n.d.). Autism spectrum disorders (ASD). [Website].

10. National Institute of Child Health and Human Development (NICHD). (n.d.). Treatments for autism spectrum disorder. [Website].

11. Centers for Disease Control and Prevention. (n.d.). Autism treatment. [Website].

12. Autism Science Foundation. (n.d.). Treatment options. [Website].

13. National Health Service. (n.d.). Diagnosis of attention deficit hyperactivity disorder (ADHD). [Website].

14. Centers for Disease Control and Prevention. (n.d.). ADHD diagnosis. [Website].

15. Children and Adults with Attention-Deficit/Hyperactivity Disorder (CHADD). (n.d.). Diagnosis of ADHD in adults. [Website].

16. Children and Adults with Attention-Deficit/Hyperactivity Disorder (CHADD). (n.d.). Treatment. [Website].

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