Autism Spectrum Disorder

ADHD and Adult Autism: Symptoms, Diagnosis & Interventions for Both

Autism and ADHD coexist at significantly elevated rates, and adults with both disorders face unique challenges. Symptoms of both conditions can resemble one another – one reason why clinicians typically screen for both during assessment. While research on adult autism and ADHD is scarce, clinicians largely agree on best practices in the evaluation and treatment of patients with both disorders.

By Benjamin E. Yerys, Ph.D. Verified Updated on April 27, 2023
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Illustration of a group of people to demonstrate adult autism and adhd

Autism spectrum disorders (ASD) and attention deficit hyperactivity disorder (ADHD) are commonly co-occurring conditions with significantly elevated prevalence rates. Though they are distinct, people with diagnoses of either autism or ADHD often struggle in similar situations. Also, autism can influence the presentation of ADHD and vice versa; accurate assessment for each is complicated and critical.

While autism and ADHD are life-long conditions for most people, research has focused almost exclusively on children because that is when symptoms first emerge. This emphasis on childhood leaves clinicians to extrapolate interventions and supports for adults. What we do know is that co-occurring autism and ADHD in adults carries unique implications and considerations that don’t exist for either condition on its own. In short, autistic who exhibit more ADHD symptoms also experience greater functional impairments.

Despite anemic research beyond childhood, there is a growing clinical consensus regarding approaches to evaluation, treatment, and support for autistic adults with a co-occurring ADHD diagnosis.

Adult Autism: Evaluation and Diagnosis

Autism Symptoms and Criteria

Autism is broadly characterized by persistent challenges in social communication and social interaction, as well as the presence of repetitive behaviors. Full diagnostic criteria for autism spectrum disorder are outlined in the Diagnostic and Statistical Manual of Mental Disorder (DSM-5). During an evaluation, clinicians look for significant challenges in the following domains to determine whether an adult is on the autism spectrum. These behaviors must be present during development, and they must cause significant impairment in functioning to warrant a diagnosis:

[Read: What Does Autism Spectrum Disorder Look Like in Adults?]

1. Deficits in Social Communication and Social Interaction

Social emotional reciprocity refers to the back-and-forth interaction that takes place with another person during social interactions and conversations. Naturally, clinicians evaluate different behaviors in adults and children.

Non-verbal communication is another way of saying body language. Clinicians evaluate the use and integration of gestures, facial expression, and other body parts in communication. Lack of eye contact while communicating is one common behavior observed in individuals on the autism spectrum. Clinicians also evaluate a person’s ability to understand non-verbal communication in others.

Developing, maintaining, and understanding relationships. Clinicians often evaluate understanding of how relationships work, differences among types of relationships (friendships, acquaintances, romantic, and family, including how the patient adjusts behavior to suit context and their level of interest in close relationships.

2. Repetitive Behaviors

Clinicians look for restrictive, repetitive patterns of behavior, interests, or activities that are maintained across the following four categories; only two categories need to be present for a diagnosis:

  • Stereotypes or repetitive motor movements, use or objects, or speech. Some examples include hand flapping, odd or unusual finger movements, and pacing; lining up toys rather than playing with them (when younger); a narrow repertoire for starting or maintaining conversations or using idiosyncratic phrasing.
  • Insistence on sameness. Autistic adults may want things to be exactly the same day after day (from taking the same route to eating the same food, for example), and will experience difficulty if routines are changed. They often experience difficulties with unexpected or rapid transitions, suffer extreme distress at small changes, and exhibit rigid thinking patterns.
  • Interests. Autistic adults can be highly fixated on interests that can span any subject or theme. Their interest and intensity level are far greater than they would be for other people, to the point that they may interfere with other activities and functioning. These interests must last for at least 3 months.
  • Sensory reactivity. Many individuals on the autism spectrum identify as having unusually strong or diminished responses to sensory information. Certain sensory inputs that would be “everyday sounds” for many people may be particularly bothersome or fascinating to people on the spectrum. Autistic adults may want to avoid certain sensory experiences because they find them aversive, or they may seek experiences they find particularly appealing. Some individuals may also have an apparent “absence” of reaction (e.g. indifference to pain and temperature).

[Read: Commonly Missed Signs of Autism in Adults]

Clinicians should also specify co-occurring conditions in the following three domains:

  • intellectual disability (present in about 30 percent of autistic people)
  • language impairment (can be receptive, expressive, or mixed expressive/receptive)
  • association with a known medical, genetic, or environmental factor (e.g., roughly 25% to 50% of people with Fragile X syndrome, particularly males, will also meet criteria for autism)

At the time of diagnosis, clinicians should also acknowledge an appropriate and helpful level of support for each patient. Many individuals who receive an ASD diagnosis in adulthood tend to fall under Level One, i.e. “requires support,” as they have developed and utilized coping mechanisms over time that allowed them to move through childhood and adulthood with enough success to not seek or be referred for an evaluation. Without supports, however, impairments may be noticeable.

Adult Autism Assessment

An autism diagnosis at any age typically follows a referral. Some factors that usually prompt a referral in adulthood include difficulty with work and relationships; “failure to launch”; and, especially in the age of social media, learning about autism and seeing personal similarities.

There is no single test that identifies autism in adulthood or at any age. There are, however, gold standard screening and diagnostic tools that clinicians use to evaluate patients for autism:

  • Detailed developmental histories help clinicians understand how a patient’s symptoms unfolded over time, and whether signs were present early in life or driven by major life changes.
  • Autism screening tools, like the Social Communication Questionnaire and the Autism Spectrum Quotient, carry some pros and cons. Some autistic individuals report that the questions do not accurately capture their experience.
  • The Autism Diagnostic Observation Schedule-2 (ADOS) includes a clinical interview and observation of the patient’s non-verbal communication and other social skills, as well as observation of repetitive behaviors.
  • An Adaptive Behavior Assessment focuses on skills needed in everyday life to achieve independence. It covers three major domains: conceptual skills (e.g. communication, cognitive tasks), daily living skills (e.g. hygiene, household management), and socialization (e.g. relationships, coping skills, hobbies). For many autistic adults, these skills can lag compared to their general intelligence, and may be a bigger barrier to living independently than any autism symptom.
  • Psychiatric assessments help ascertain an autism diagnosis by ruling out other conditions that could explain symptoms. Common diagnostic differentials for autism include social anxiety, generalized anxiety disorder, ADHD, and obsessive compulsive disorder (OCD).

Adult Autism and ADHD

Though little research exists on autism and ADHD in adults, some studies estimate that the disorders coexist at rates between 20% and 37%.1 2

ADHD is characterized by symptoms of inattention, hyperactivity, and/or impulsivity – different from the social communication symptoms and restricted behaviors associated with autism.

Still, some ADHD symptoms relate to the diagnostic criteria for autism. Not listening when spoken to directly, for example, is indicative of inattention, a common ADHD symptom. But given the strong social demands embedded in rating a person on this symptom, it could also indicate autism. If an adult is not making eye contact during a conversation, then it may give the appearance of ‘not listening when spoken to directly’. Differential psychiatric assessments as well as other diagnostic tools can help clinicians determine whether this symptom stems from distractibility (which indicates ADHD) or from deficits in social-emotional reciprocity and nonverbal communication (which indicate autism).

It’s critical for clinicians to consider whether an ADHD symptom appears in non-social situations. If a patient reports feeling distracted when working alone and without social demands, that may indicate ADHD more than autism. Distractions should be further analyzed – is the patient daydreaming, or are they being pulled into a sound they hear that may be bothering them? The latter may indicate sensory sensitivity related to autism.

ADHD in Autistic Adults: Outcomes

Greater functional impairments exist in autistic adults as more ADHD symptoms are present. That’s according to a recent study involving 724 autistic adults who were asked about the frequency and severity of behaviors associated with autism and ADHD, their quality of life, and other aspects of living. In all cases, comorbid ADHD explained measurable variances in adaptive behaviors compared to controls.3

Adult Autism and ADHD: Treatment and Interventions

There are currently no studies available on the use of ADHD treatments with adults with both ADHD and autism diagnoses. Most treatment recommendations for adults have been adapted from research on autistic children.

Clinicians, however, generally agree on the supports and therapeutic interventions that matter most to autistic adults with ADHD — and which ones increase independence and improve quality of life, as highlighted in a recent paper authored by ASD and ADHD researchers. The recommendations cover pharmacological and non-pharmacological interventions, as well as behavioral and environmental approaches in work and higher education. They include but are not limited to:

Non-pharmacological Interventions

  • Cognitive behavioral therapy (CBT), cognitive remediation therapy, and similar approaches; specific adaptations may be necessary for individuals with social communication and intellectual limitations. Adults may respond better to group-delivered treatments than do children.
  • Therapies focusing on executive function; Flexible Futures is an upcoming program that targets these skills in autistic adults with ADHD (a children’s version, Unstuck and On Target, is available and has research supporting its efficacy).
  • Psychoeducation helps to support many patients and families.

Educational/Vocational Supports

  • Identifying realistic career goals
  • Seeking volunteer opportunities to learn about the work environment
  • Using supports for completing applications and job interviews
    Identifying and seeking adjustments and accommodations at work or school (Standardized accommodations like extended time on tests, for example, may not be suitable for autistic adults with an ADHD diagnosis, who may benefit more from a mid-point break)
  • Coaching to support long-term goals
  • Using strategies to aid concentration and reduce anxiety
  • Adopting assistive technology devices
  • Making use of organizational supports (peer systems, skills training)

Pharmacological Interventions

Pharmacological treatments for co-occurring ASD and ADHD in adults do not differ significantly from the treatments used with each disorder individually. Stimulant and non-stimulant medications are commonly prescribed to treat ADHD. Though there are no FDA-approved pharmacological medications to address core symptoms of ASD, antipsychotics like risperidone and aripiprazole are often used to address anger and irritability. Behavioral and environmental interventions, however, are more common and appropriate first-line approaches for targeting core autism behaviors.

Still, expert consensus is that prescribers should start on low doses and move slowly through treatment, as adults with both conditions may be more treatment resistant and sensitive to medication. The goals and targets for medications (as with any intervention) should also be clarified at the outset along with measures of effectiveness.

Other best practices:

  • Adults with ASD and ADHD diagnoses may be unable to swallow medications in pill/tablet form due to sensory issues and/or physical difficulties. Clinicians should consider liquid formulations and alternative preparations.
  • Some adults may have difficulty describing their thoughts, feelings, and sensations, which could impact patient feedback on treatments. Clinicians should use visual tools, including mood scales and drawings, to aid with reporting.

The content for this article was derived from the ADDitude Expert Webinar “Do I Have Autism? ADHD? Both? An Adult’s Guide to Diagnosis and Treatment”  [ADDitude ADHD Experts Podcast Episode #354] with Benjamin E. Yerys, Ph.D., which was broadcast live on May 11, 2021.

Adult Autism and ADHD: Next Steps

The Clinicians’ Guide to Differential Diagnosis of ADHD from Medscape and ADDitude

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1 Hollingdale J., Woodhouse E., Young S, Fridman A, Mandy W. (2019) Autistic spectrum disorder symptoms in children and adolescents with attention deficit/hyperactivity disorder: a meta-analytical review. Psychol Med, BMC Psychiatry. 19:404. https://doi.org/10.1186/s12888-019-2284-3

2 Lai, M. C., Lombardo, M. V., & Baron-Cohen, S. (2014). Autism. Lancet (London, England), 383(9920), 896–910. https://doi.org/10.1016/S0140-6736(13)61539-1

3 Young, S., Hollingdale, J., Absoud, M. et al. (May 2020). Guidance for identification and treatment of individuals with attention deficit/hyperactivity disorder and autism spectrum disorder based upon expert consensus. BMC Medicine 18, 146. https://doi.org/10.1186/s12916-020-01585-y